WO1993016204A2 - Process and apparatus for extracting solutes from their aqueous solutions - Google Patents

Abstract

Nickel and/or copper cations can be extracted, from their aqueous solutions also containing chelating agents, by liquid-liquid extraction with an organic solvent containing suitable complexing extractants for the nickel and/or copper. However, with the most efficient such complexing extractants, the phenolic ketoximes and aldoximes, the pH of the aqueous solutions to be extracted should be substantially more alkaline than those known in the prior art for extraction of solutions with about the same amounts of extractable metals but without chelating agents. Apparatus for carrying out the extraction process includes a tank for permanently containing an organic solvent, and a plurality of pumps and valves operable for transferring aqueous feed solution from a source thereof to the organic solvent tank, for mixing therewith, thereafter draining off the raffinate, followed by transferring regenerant solution into the organic solvent tank for regenerating the solvent, followed by draining off the used regenerant solution.

Description

DESCRIPTION

PROCESS AND APPARATUS FOR EXTRACTING SOLUTES FROM THEIR AQUEOUS SOLUTIONS

FIELD OF THE INVENTION

This invention relates to a process for extracting copper, nickel, or both nickel and copper from aqueous so¬ lutions that contain these metals as cations together with chelating agents for the metal ions, particularly the che¬ lating agents commonly used in electroless plating baths. The process is particularly advantageous for recovery of metal values from spent solutions for electrolessly plating nickel or copper. This invention further relates to an apparatus or system broadly applicable for extracting solutes from aqueous feed solutions.

STATEMENT OF RELATED ART

The general use of complexing agents soluble in water- immiscible organic solvent to extract metal values from aqueous solutions is well known and is described with re¬ spect to the extraction of copper in particular in U. S. Patent 4,507,268 of Mar. 26, 1985 to Kordosky et al. This reference, particularly in columns 2 and 3, also gives the commercial names and chemical characterizations of many of the commercially available complexing agents known for this purpose.

The metal plating industry has come under increasing environmental regulatory pressure within the last two dec- ades, and is increasingly faced with the need to comply with rules that severely restrict the amounts of metals such as copper and nickel that they can discharge to waste water effluents or in solid form to landfills. Electroless plating presents a special problem in this regard, because the chelating agents that are usually present in electro- less plating baths tend to render conventional metal remov¬ al methods, such as hydroxide precipitation or extraction by ion exchange resins, inefficient and incomplete. Also, acids and/or salts of metals other than the metal desired to be plated from the bath are formed as the metal content of an electroless plating bath is transferred to the plat¬ ing formed. The metal content can be, and in large scale commercial applications of electroless plating usually is, replenished by adding more salt(s) of the metal to be plat- ed, but the accumulation of other salts eventually causes the plating performance to fail to meet at least one of the required quality criteria for the plating, such as speed of plating, appearance of the plate, hardness of the plate, or the like. The bath then must be discarded, even though its concentration of platable metal ions is as high or nearly as high as when the bath was freshly prepared. W. Ying et al.. Journal of Hazardous Materials 18 (1988) , 68 - 89 re¬ view the characteristics of electroless nickel plating baths and treatment of spent baths to meet anti-pollution restrictions on the discharge of nickel to waste streams. They conclude that precipitation of the nickel by pH ad¬ justment is the most economical method for meeting the re¬ quirements.

U. S. Patent 4,303,704 of Dec. 1, 1985 to Courdevulis et al. teaches recovering copper and/or nickel from waste waters in which they are present together with chelating agents by passing the waste waters through an ion exchange column packed with exchanger having an iminodiacetic acid functionality. DESCRIPTION OF THE INVENTION

Except in the claims and the operating examples, or where otherwise expressly indicated, all numerical quant¬ ities in this description indicating amounts of material or conditions of reaction and/or use are to be understood as modified by the word "about" in describing the broadest scope of the invention. Practice within the exact numeri¬ cal limits stated is generally preferred. Summary of the Invention

As noted above, nickel and copper can readily be ex¬ tracted from most of their aqueous solutions previously in¬ vestigated by use of liquid-liquid extraction with oximes and/or some other complexing extractant molecules dissolved in a water-immiscible solvent, and such extractions are normally effective over a wide range of pH values for the aqueous solutions to be extracted. However, attempts to extract nickel from spent electroless plating solutions with conventional complexing agents dissolved in a water immiscible solvent were unsatisfactory, because the frac¬ tion of the metal values present in the aqueous solutions that was extracted in a single extraction stage was found to be far less than expected from other extractions of aqueous solutions containing similar amounts of nickel at similar pH values. It has now been found that these ini¬ tially unsatisfactory results were apparently due to the presence of chelating agents for nickel in the aqueous so¬ lutions commonly used for electroless nickel plating, and that both nickel and copper ions can be effectively and efficiently extracted from their aqueous solutions that also contain chelating agents for the ions, for example, by assuring that the aqueous solutions have a pH value within a properly selected range before use of liquid-liquid ex- traction of the aqueous solutions. The extraction is pref¬ erably accomplished with an immiscible organic solvent con¬ taining an organic oxime or organic hydroxyquinoline com¬ plexing extractant agent. The pH value that is optimum for extracting aqueous solutions of nickel or copper that also contain chelating agents is generally substantially differ¬ ent from the value that would be expected to be optimum, based on the experience of the prior art with other types of aqueous solutions that do not contain substantial amounts of chelating agents but do contain about the same concentrations of nickel and/or copper. After extraction, the metal values can be recovered from the organic cosol- vent phase by extraction with aqueous acidic solutions in a manner that is conventional per se. An optional step that is often highly advantageous for use in connection with this invention is to wash the organic cosolvent phase with a suitable aqueous wash liquid, as further described below, before the metal values are extracted with an aqueous acidic solution.

A process according to this invention can be and often is applied to extract substantially all of the content of extractable metal(s) in an aqueous solution to be treated. However, if the aqueous solution to be treated contains both nickel and copper, it may be possible and desirable to extract predominantly only one of these metals, by proper choice of the extractant complexing agent and/or of operat¬ ing conditions. Various embodiments of the invention include the ex¬ traction process itself and combinations of the extraction process with metal plating, particularly electroless plat¬ ing. In its simplest form, one embodiment of a process ac¬ cording to this invention includes a step of contacting (i) an aqueous solution containing extractable metal ions and chelating agent molecules for these extractable metal ions and having an appropriate pH with (ii) a water-immiscible solvent phase containing a complexing extractant for the nickel and/or copper to be extracted. Preferably, the com- plexing extractant is selected from the group of alkyl sub¬ stituted phenolic ketoximes, alkyl substituted phenolic al- doximes, and alkyl substituted 8-hydroxyquinolineε, more preferably all containing from 7 to 17 total carbon atoms in the alkyl substituents. The contact occurs over a suf- ficiently large interfacial area for a sufficient time at an appropriate temperature to result in the transfer of at least part of the content of the extractable metal ions in¬ itially in the aqueous solution into the water-immiscible organic solvent phase, where the metal is believed to be dissolved in the form of a complex of the metal ions by the oxime or hydroxyquinoline, when this type of complexing extractant is used. The metal ions may be, and preferably are, recovered from this water-immiscible organic solvent phase, as may be readily accomplished by extraction with strong acid, in a manner that is conventional in itself, when a phenolic oxime or an 8-hydroxyquinoline complexing agent is used as the complexing extractant. The basic ex¬ traction and/or the recovery process may be, and generally preferably is, divided into multiple stages in a manner well known in the art. A flow diagram for a three stage process is given, for example, in U. S. Patent 4,957,714 of Sep. 18, 1990 to Olafson et al.

In another embodiment of the invention, a system is provided that may be generally applied for use in extracting solutes from aqueous feed solutions. All of the embodiments of the system or apparatus include mixing tank means for permanently containing an organic solvent that is less dense than water. The organic solvent never leaves the mixing tank in any processing cycle. In certain extraction applications, such as the extraction of amino acids from fermentation broth, the system only requires in addition to the mixing tank, a feed tank for receiving the aqueous feed solution for processing, and a regenerant tank for containing regenerant solution for regenerating the organic solvent in the mixing tank after an extraction cycle. A controller is programmed for controlling pumps and control valves in transferring aqueous feed solution to the mixing tank for mixing with the organic solvent, for causing the organic solvent to extract solute from the aqueous feed solution. After extraction, and a predetermined settling or quiescent time, an aqueous phase substantially depleted of solute is pumped from the mixing tank to a raffinate holding tank for later processing. Regenerant solution is then pumped from the regenerant tank into the mixing tank, for mixing with the organic phase, for regenerating the organic solvent by causing the solute to be transferred to the regenerant solution. After a quiescent time, the used regenerant solution phase iε pumped from the mixing tank back to the regenerant solution tank for reuse. The regenerated organic solvent is then ready for mixing with a new batch of aqueous feed solution, in a subsequent extraction cycle. The present inventors discovered that by retaining the organic solvent in the mixing tank at all times, an improved and more efficient system is provided relative to the prior art.

In another embodiment of the invention, the inventors conceived mechanisms for substantially eliminating cross- contamination of fluids, involved in processing in the mixing tank, by residual fluid left in common fluid paths with the mixing tank from a prior cycle or operational step. To accomplish this, whenever a processing step requires that fluid be drained from the mixing tank, an associated interface pot or tank is provided in association with that drainage step, whereby after the primary draining step is completed, means are employed for immediately thereafter further draining fluid from the mixing tank and all fluid lines and control valves that have a common open fluid path with the mixing tank, whereby all of these common paths are drained into the associated interface tank, for insuring that prior to the next processing step these fluid lines all have a common fluid composition substantially the same as that presently existing in the fluid in the mixing tank before the next processing step. In this manner, cross-contamination is substantially eliminated. In certain applications, means are included for draining from the mixing tank to an interface pot prior to initiating a primary drainage step, and after completing the primary drainage step. This eliminates contamination of the extracted aqueous with organic and unextracted aqueous held up in the drain lines and valves.

In still other embodiments of the system for the present invention, a first wash tank may be added for containing wash solution that is transferred from the first wash tank to the mixing tank, for washing the organic phase remaining in the mixing tank after an extraction cycle, to remove contaminants from the organic phase. After washing, and a quiescent time, fluid transfer means are used to transfer the used first wash solution back to the first wash tank.

In yet other applications, a second wash tank is included for containing a second wash solution, that is transferred to the mixing tank by transfer means after regeneration of the organic solvent, for washing the organic solvent to remove contaminants therefrom, in preparation for the next extraction cycle. Thereafter, fluid transfer means are used to remove the used second wash solution from the mixing tank back to the second wash tank, or in certain applications to the first wash tank if the used second wash solution has a pH level rendering it applicable for use as a first wash solution. The present inventive system in its various embodiments optimizes the use of the inventive process taught herein.

Brief Description of The Drawings

The system or apparatus of the present invention is described below with reference to the drawings, in which like items are identified by the same reference designation, wherein:

Fig. 1 is a process control logic flow diagram for one embodiment of the invention. Figs. 2A and 2B show a flow schematic diagram for one embodiment of the invention.

Fig. 3 is a detailed view showing phase detection, control valve, and manifold apparatus for the embodiment of the invention of Fig. 2. Fig. 4 is a simplistic sectional view of a normal valve configuration for a typical control valve.

Fig. 5 shows a modified valve configuration for the control valve of Fig. 4, for one embodiment of the invention. Fig. 6 shows a side elevational view of an impeller configuration for one embodiment of the invention.

Fig. 7 shows a top view of the impeller of Fig. 6. Fig. 8 shows a process control logic flow diagram for another embodiment of the invention.

Figs. 9A and 9B show a flow schematic diagram for another embodiment of the invention for carrying out the process of Fig. 8.

Fig. 10 shows a detailed view of phase detection, control valve, and manifold apparatus for the embodiment of the invention employed in the system of Fig. 9.

Description of Preferred Embodiments

With increasing preference in the order given, the concentration of metal ions of the type(s) selected to be extracted within the aqueous solutions to be extracted ac¬ cording to this invention is within the range from 0.01 to 100, from 0.2 to 45, from 0.5 to 20, from 1 to 15, or from

2 to 10 grams per liter (hereinafter abbreviated as "g/L") .

Chelating agents that are present together with the metal values to be extracted in a process according to this invention may include any aqueous-soluble organic mole- cules, except phenolic oximes and substituted 8-hydroxy quinolines, that contain two or more functional groups, each of which includes an atom with an unshared electron pair capable of complex-forming donation to the metal ions concerned, provided that at least two of these functional groups are positioned within the molecule so as not to be sterically hindered from forming a complex coordination bond with a single metal atom, to form at least one chelate ring therewith. The most common and preferred functional groups of this type are carboxylate, hydroxyl (including carboxyl, which, along with carboxylate, is to be under¬ stood herein as a single donor group) , amino, phosphonic and phosphonate, and sulfonic and sulfonate. Chelating agents containing at least one, or more preferably at least two, carboxylate or carboxyl electron donating groups are preferred for this invention. Non-limiting examples of such preferred chelating agents for use when the metal cat¬ ions are nickel include citric, malic, tartaric, succinic, lactic, hydroxyacetic, and aminoacetic acids and their salts, and organic diamines. Non-limiting examples of such preferred chelating agents for use when the metal cations are copper include multi-dentate phosphonic acids, amino acids and amino alcohols, especially nitrilotriacetic acid ("NTA") , aminodiacetic acid, nitrilotrimethylenephosphonic acid, and (ethylenedinitrilo)-tetra(methylenephosphonic acid) . Particularly preferred chelating agents with copper include (ethylenedinitrilo)-tetraacetic acid (hereinafter abbreviated "EDTA") and its salts and N.N.N' .N'-tetrakis-2- hydroxypropyl-ethylenedia ine (hereinafter denoted as QUAD- ROL™) .

With increasing preference in the order given, it is preferred that the total concentration of chelating agents in solutions to be extracted according to the process of this invention be sufficiently high to chelate with at least 1, 5, 10, 25, 50, or 100% of the type of ion(s) se¬ lected for extraction that are present in the same solution with the chelating agents. Any substantially water immiscible liquid solvent can be used for solution of the oxime. Typically the solvents are the aliphatic and aromatic hydrocarbons, halohydrocar- bons, and halocarbons. Aliphatic hydrocarbons such as al- kanes, including cycloalkanes, and halogenated alkanes are suitable. Preferred alkanes have a minimum of five carbon atoms. Preferred halogenated alkanes have a minimum of two carbon atoms. Aromatic hydrocarbons which can be used in¬ clude benzene, and substituted products such as toluenes, xylenes and cumene. Also suitable as solvents are those esters, ethers, ketones and alcohols which are substantial¬ ly water immiscible and preferably contain not more than one moiety selected from the group consisting of: 0 0 0 -0-C II-, -CII-, -CI-, -CI-O-CI- per molecule of solvent and no other atoms except carbon, hydrogen, and halogen atoms. It is preferred that the sol¬ vent used have a solubility in water, at the temperature at which the process of extraction is performed, not greater than 1.3, 0.8, 0.2, 0.1, 0.02, 0.005, 0.001, or 0.0005% by weight, with increasing preference in the order given. Furthermore, any blend of these substances with a water im- miscible kerosene is also suitable. Practically preferred organic solvents are aliphatic hydrocarbons having flash points of 65° C and higher and solubilities in water of, with increasing preference in the order given, less than 0.1%, 0.04%, or 0.005% by weight. These solvents are chem- ically inert and the costs thereof are currently within a practical range. Representative commercially available solvents of this type are: Kermac™ 470B (an aliphatic kerosene available from Kerr-McGee, with a flash point of 79° C) ; Kermac™ 400-500, an aliphatic kerosene similar to Kermac™ 470B, but having a flash point of 82° C; Chevron Ion Exchange Solvent (available from Standard Oil of Cal¬ ifornia) , with a flash point of 91° C; Escaid™ 100 and 110 (available from Exxon-Europe, with a flash point of 82° C) ; Exxsol™ D 80, available from Exxon USA and corresponding to Escaid™ 110; Norpar™ 12 (available from Exxon USA, with a flash point of 71° C) ; Aromatic 150 (an aromatic kerosene available from Exxon USA, with a flash point of 66° C) ; Conoco C 1214L (available from Conoco, with a flash point of 71° C) , and various other kerosenes and petroleum frac- tions from other oil companies.

The complexing agent used in the organic phase may be selected from among any type of molecules that are capable of forming with copper cations, nickel cations, or both copper and nickel cations, a complex that is more soluble in the organic solvent component used in the organic phase than it is in water. The complexing agent is preferably selected from the group consisting of phenolic ketoximes and aldoximes conforming to the general chemical formula

(I):

(R)

where a is a positive integer with a value in the range from 1 to 4 inclusive; each of the number "a" of R groups present in the molecule is independently selected from the group consisting of saturated aliphatic moieties having one free valence and from 1 to 25 carbon atoms, ethylenically unsaturated aliphatic moieties having one free valence and from 3 to 25 carbon atoms, and moieties conforming to the general chemical formula -O-R¹ * , where R' • is selected from the group consisting of saturated aliphatic moieties having one free valence and from 1 to 25 carbon atoms and ethylen¬ ically unsaturated aliphatic moieties having one free val- ence and from 3 to 25 carbon atoms; and R¹ is selected from the group consisting of hydrogen, saturated aliphatic moie¬ ties having one free valence and from 1 to 25 carbon atoms, ethylenically unsaturated aliphatic moieties having one free valence and from 3 to 25 carbon atoms, and moieties conforming to the general formula -CH₂C₆H₄-R* ' , where C₆H₄ represents a benzene ring minus two hydrogen atoms, which may be from any two positions on the ring, and R¹ ' has the same meaning as above; all with the proviso that the total number of carbon atoms in the group R¹ and the "a" R groups is in the range from 3 to 25. More preferred compounds conforming to formula I are those in which a = 1, R is a straight or branched chain alkyl group having from 7 to 12 carbon atoms and attached to the position para to the hy¬ droxyl group, and R' is hydrogen or methyl. A particularly preferred group of complexing agents is ketoximes, especi¬ ally 2-hydroxy-5-nonylbenzophenone oxime, 2-hydroxy-5-do- decylbenzophenone oxime, 2-hydroxy-5-nonylacetophenone ox¬ ime, 2-hydroxy-5-dodecylacetophenone oxime, 2-hydroxy-5-oc- tylacetophenone oxime, 2-hydroxy-5-heptylacetophenone ox¬ ime; and aldoximes, especially 2-hydroxy-5-octylbenzaldox- ime, 2-hydroxy-5-nonylbenzaldoxime, 2-hydroxy-5-dodecyl- benzaldoxime, 2-hydroxy-5-heptylbenzaldoxime, and mixtures thereof, particularly mixtures of only ketoximes or of only aldoximes. The ketoximes and aldoximes employed are sub¬ stantially water insoluble and are soluble in organic sol- vents.

Although generally less preferred than the ketoximes and aldoximes, alkyl-substituted 8-hydroxyquinolines with the same numbers of total carbon atoms in the alkyl sub- stituents as described for the aldoximes and ketoximes con- forming to formula I above and the same types of substitu- ents as described for R above may also be used as the com¬ plexing agents in the organic extractant phase. Among the hydroxyquinolines, those with alkyl substituents at the 7 position are most preferred. Modifiers can be added to the organic phase, in addi¬ tion to the complexing agent, in order to modify or improve the extraction of the metal. Substances which are pre¬ ferred as modifiers if modifiers are to be used are straight or branched chain alcohols having from 6 to 30, or more preferably from 8 to 20, carbon atoms, such as isodec- anol, 2-ethylhexanol, and tridecanol; phenols such as the 6 to 20, or more preferably, the 8 to 12 carbon atom alkyl substituted phenols e.g. , nonyl phenol; branched chain est¬ ers containing from 6 to 30 carbon atoms, e.g. , 2,2,4-tri- methyl-l,3-propanediol diisobutyrate; and various organo- phosphorus compounds such as tributylphosphate (cf.. e.g. , Ritcey et al.. Transactions of the International Solvent Extraction Conference, 1974, pp. 2437 - 2481) ; any or all of which can be added to improve stripping, solubility, phase separation and/or other important characteristics of the organic solution. When typically employed in the ex¬ traction step, the modifier will be employed in amounts up to about 25 % in the organic solution. Generally, however, no modifier is needed in a process according to this inven¬ tion.

The amount of complexing agent in the organic phase is not critical and may vary between wide limits. However, the complexing agent will preferably be present in an amount of 1 - 50% by weight of the organic phase, more preferably about 5 - 20%. The amount of complexing agent in the organic phase which is present relative to the metal in the aqueous phase is a function of both the concentra¬ tion of complexing agent and of the volume of organic phase relative to the volume of the aqueous phase. The amount of complexing agent in the organic phase should be sufficient to extract the desired metal values from the aqueous phase, and accordingly the ratio of the total amount of the com¬ plexing agent in the organic phase to the total amount of metal selected to be extracted in the volume of aqueous phase that is mixed with organic phase containing complex¬ ing agent in a single extraction stage according to the in- vention preferably is at least 2:1, more preferably at least 2.5:1, and still more preferably at least 3:1, all these ratios being on a molar basis.

The respective volumes of the aqueous and organic phases in the various extraction and stripping steps are generally determined by the individual needs of the pro¬ cesses performed, such as the type of complexing agent, solvent, metal selected to be extracted, and equipment employed, and the relative concentration of the solutions. The organic phase (O) to aqueous phase (A) volume ratios (O/A) preferably varies from 1:20 to 20:1. More desirably, an effective range of organic to aqueous phases (O/A) is 1:5 to 5:1 and commercial systems will preferably employ a ratio of 1:3 to 3:1.

It is normally preferred that a process according to the invention be a continuous, countercurrent process in which the organic phase is recycled for reuse. The process may, however, be carried out as a batch process. The organic extractant phase should contact the aque¬ ous metal containing phase for a sufficient length of time and with sufficiently vigorous mechanical agitation to re¬ sult in transfer of at least part of the metal content of the aqueous solution into the organic phase. The time of contact depends on the particular system, the type of equipment used, and upon individual needs and desires. As a general rule however, the contact time between the organ¬ ic complexing extractant solution and the aqueous solution should be in excess of 0.1 seconds with some equipment, but generally less than 3 hours. Naturally a minimum contact time is desired, thus a more desirable phase contact time would be in the range of from 5 seconds to 2 hours, while a still more preferred contact time is from about 1 minute to about 1 hour.

After the metal has been extracted or transferred to the organic phase, the two phases are separated by any con¬ venient means for a liquid/liquid phase separation. Rep¬ resentative, but non-exhaustive, examples of means for achieving phase separations include gravity settlers and centrifuges. Generally any system used to separate dif¬ ferent liquid phases may be used.

It is preferable, with increasing preference in the order given, to operate an extraction step according to this invention under conditions such that the fraction of the total amount of extractable metal cations initially present in the aqueous phase that is transferred to the organic phase after completion of contact is at least 50, 75, 90, 92, 95, 98, 99, 99.5, 99.9, or 99.97 %. In cases such as those of waste treatment addressed in this invention, complete (99-99.9%) metal extraction is us¬ ually desired, along with high concentration of the metal into a pure product strip solution, and even small amounts of cross-contamination can have serious consequences. For example, in the extraction of nickel from spent electroless nickel, it is desirable to produce extracted raffinate hav¬ ing a nickel concentration of 5 pp , and preferably less than 1 ppm. But when producing a strip product solution of 100 g/L nickel, if only 0.01% of the strip solution remains unmixed in the drain/valve system during extraction, but then is discharged with extraction raffinate, it would con- tribute 10 ppm of Ni to the average nickel content, poten¬ tially throwing the raffinate out of target discharge lim¬ its even if the extraction step itself had removed all the nickel from the feed.

Precise interface separation, even in principle, is difficult for two reasons: (1) the physical arrangement of the drainage tube and valves normally introduce some cross- contamination due to the small but finite volumes of ex¬ traction liquid(s) which are retained in them; (2) real solutions often produce mixtures of organic and aqueous phases, often referred to in the art as "rag" or "crud", which persist near the interface and lead to cross-con¬ tamination. It is an objective of this invention to pro¬ vide means for overcoming these cross-contamination prob¬ lems, and permit the efficient use of readily automated batch solvent extraction processes. It is a further ob¬ jective to provide effective processes and equipment for treatment of waste electroless (chelated) nickel and copper solutions. These objects are furthered by use of an op¬ tional step or stage of washing of the organic cosolvent phase containing extracted metal values with an aqueous washing phase before the organic cosolvent phase is sub¬ jected to stripping of the metal values with an aqueous acid stripping phase.

While one may use a batch of such washing phase only once and then discard it, economic consideration may favor re-using it several times, preferably discarding and re¬ plenishing only a percentage of it after each use. The purpose of the washing stage is to remove impurities from the loaded organic, but leave the desired metal values as little affected as is practicable. Achieving such selectivity is often aided by controlling pH conditions during wash. The mechanical aspects of our batch system (screen placement, valving system, interface removal, and the like) may be used to handle a wide variety of solvent extraction applications, but generally as already noted above, alka- line conditions are favored for extracting metals such as nickel and copper from solutions of these metals that also include chelating agents. This means that, in addition to extracting other metals that may be present in the extrac¬ tion feed, the loaded organic cosolvent phase will tend to contain acid-consuming components which, if transferred to strip solution, would use up acid unproductively and con¬ taminate the strip solution. In the case of spent electro¬ less nickel treatment, the initial feed solution may be made alkaline with ammonium or sodium hydroxide. The organic phase may transfer alkalinity by entrainment or, when ammonium hydroxide is used, by actual loading of am¬ monia into the extractant; in either case alkalinity is preferably removed by washing prior to stripping. In ad¬ dition, non-nickel metals such as zinc may also be loaded into the organic cosolvent phase and be undesirable to transfer into the same acid stripping solution as the nickel.

A wide range of washing equilibrium pH values, from a low value of 3.5 up to as much as pH 10, can be advantage- ously used to remove alkalinity. Values of pH no higher than 8 are preferred to remove ammonia, and values of pH no higher than 10 to remove sodium hydroxide. In the case of unmodified aldoxime extractants (such as LIX 860) with electroless nickel, it is preferred for zinc removal that the washing equilibrium pH after washing be in range 3.7 to 5.5, and more preferably in the range 4.0 to 5.0. Lower values will tend to remove larger quantities of nickel from the loaded organic phase, and higher values will tend to leave significant portions of zinc in the washed organic phase. Ammonia will be removed under all these conditions, as well as at higher pH values.

To assure that the pH remains in this rather narrow range, it is desirable to use a buffer mixture in the wash solution. For electroless nickel treatment a buffer of acetate/acetic acid is preferred, since its buffering range can be readily adjusted to any value within the preferred range of 3.7 - 5.6; the total amount of acetate (whether as ionic acetate or acetic acid) can be from 0.05-1 M, pref¬ erably from 0.1 - 0.5 M, and more preferably from 0.2 - 0.4 M. To assure that the equilibrium pH remains within the desired range, the initial pH must be sufficiently low (or, expressed another way, the washing solution must have enough residual acidity) to neutralize organic alkalinity and strip the zinc, without consuming all the buffer ca¬ pacity. This means that the initial pH of the wash solution should be held to the range 3.5 to 4.5, preferably 3.7 to 4.2.

If the level of contaminants (ammonia, sodium, zinc, and the like) removed in the wash stage is sufficiently low (this is determined by the rate at which they are carried over by physical means to strip solution) , the wash solu- tion may be re-used for the next cycle of loaded organic phase. In each cycle, the pH of the used wash solution is adjusted as needed back to the target initial pH by addi¬ tion of acid such as sulfuric acid. Preferably, a portion of the wash solution is bled off after each washing contact with the organic cosolvent phase, the volume thus subtract¬ ed is replenished with water and buffer component (such as acetic acid) , and then the pH is adjusted to the target initial pH before the next contact. This permits the wash solution to operate with an acceptable steady state concen- tration of impurities, so that the amount of impurity en¬ tering the wash solution from a single contact with loaded organic is equal to the amount of impurity leaving the wash solution each cycle via the bleed stream. As a fraction of the total volume of wash solution, the bleed stream can be as little as 1% (for slow impurity buildup, or where the impurity tolerance in the strip solution is high) or as high as 100 % (total replacement of wash solution each cycle, for systems with high impurity transfer, and low tolerance of impurity in the strip solution) . Preferred bleed solution rates are normally in the range of 2 - 50 %, more preferably 5 - 20 %, of the total volume of the wash- ing solution being bled after each stage of contact with the organic cosolvent phase being washed.

Although the wash solution can initially be simply water, this is not preferred because the low ionic strength of water results in poor phase disengagement properties, leading to high entrainment of organic phase in the wash liquid. It is preferred to have ionic solutes of at least 0.05 total ionic molarity (defined as the sum of the molar- ities of all the ionic species in solution) up to 5 total ionic molarity, and more preferred to have at least 0.1 up to 1.0 total ionic molarity, in the wash solution. If the wash solution is extensively recycled, this level may be reached automatically at steady state operation. If not, it is preferred that a salt be added to the wash solution. A preferred salt to be added is the sodium salt of the acid used in stripping. Where sulfuric acid is the stripping acid, the preferred salt to be added is sodium sulfate. Where the wash solution is used only once (100% bleed) , the preferred concentration of sodium sulfate is 0.02 to 0.4 molar, and more preferably 0.04 to 0.15 molar. Stripping, also referred to as regeneration, is normally carried out with an aqueous solution of a strong acid. The choice of acid is dependent on factors including cost, corrosivity, solubility, and the desired form of the product. Sulfuric and hydrochloric acids are preferred acids.

A separate step of washing the organic cosolvent phase after stripping but before recycling it to a second extrac¬ tion stage may advantageously be used to prevent stripping solution components (primarily acid) from interfering with extraction. In systems where the acid level in the strip¬ ping solution is low, or where transfer of small amounts of acid from stripping solution to the organic cosolvent ex- traction phase do not cause operational difficulties (i.e., where the extraction feed solution is effectively bufferred sufficiently so the pH does not drop below the level needed for complete metal extraction) , a wash stage after strip- ping is not usually needed. This is the case for electro¬ less nickel where ammonia is used to raise the pH for ex¬ traction. But in systems where acid transfer does impair completeness of metal extraction, a wash stage is most preferably interposed after stripping and before extrac- tion. An example is the extraction of copper from solu¬ tions including complexing agents such as EDTA (ethylene- dia inetetraacetic acid) ; adjustment of feed pH to 12 using alkali such as sodium hydroxide produces little buffering capacity beyond that of hydroxide, and introduction of even small amounts of extraneous acid, such as that carried over from stripping, can lower the pH below the desired extrac¬ tion range of 10 - 10.5).

In such cases, the stripped organic is advantageously washed with an aqueous solution, wherein the acid associat- ed with the organic is largely removed to the aqueous phase. Again, this wash solution should preferably have a minimum ionic strength of at least 0.05 M to avoid problems with phase disengagement. The aqueous phase may be pre- adjusted with alkali or an acid-consuming buffer to assure that the equilibrium acid concentration is low. The aque¬ ous phase exiting this stage may be reused in a subsequent cycle, optionally after re-adjustment of pH with additional base. Alternatively, the exiting aqueous phase, which car¬ ries some acid values, may be used in the stage of washing the loaded organic; the acid values from washing of stripped organic are thus used to neutralize excess alka¬ linity in the loaded organic. A further alternative is the use of the aqueous phase exiting from the washing of loaded organic cosolvent phase to wash stripped organic cosolvent phase, similarly using the alkali removed from loaded or¬ ganic to neutralize excess acid in the stripped organic.

Thus a preferred mode of operation for the treatment of electroless nickel solutions uses the following steps:

(1) Waste electroless nickel feed solution, typically con¬ taining about 5.0 g/L Ni, is adjusted to a pH of about 9 using ammonia, ammonium hydroxide, or a mixture of sodium hydroxide and ammonia/ammonium hydroxide.

(2) The pH-adjusted feed is added to the mixing tank con¬ taining an organic solution made up of LIX™ 860 (5-dodecyl- salicylaldoxime) in kerosene at about 0.6 molar, and the phases are mixed. Any aqueous/organic mixture from the extraction interface pot is also added. Extraction is typ¬ ically complete in less than 15 minutes; the extracted aqueous phase (raffinate) is withdrawn for disposal. The raffinate will typically contain less than 5 ppm Ni, often less than 1 ppm, depending on the source of electroless solution.

(3) Step 2 may be repeated one or more times depending on the concentration of nickel present in the extraction feed. After the last extraction raffinate is withdrawn, the small amount of remaining aqueous phase, the interface and any associated unseparated organic/aqueous mixture, and a small amount of organic phase are withdrawn to the extraction in¬ terface pot.

(4) An extraction-wash solution containing a 0.2 molar acetic acid-acetate buffer at about pH 4 is added to the loaded organic in the mixing tank, along with the contents of the extraction-wash interface pot, and mixed for 5 - 15 min. The separated wash solution will typically rise 0.3 to 0.5 pH units compared to its beginning pH, and will have removed from the loaded organic substantially all of the ammonia, 95 - 100 % of the zinc, but only 0.1 % or less of the nickel. The separated wash aqueous phase is removed from the mixing tank, a portion (5 - 20 %) is bled off for disposal, the bled volume is replaced with an equal volume of 0.2 molar acetic acid, and the pH is adjusted to pH about 4 by addition of sulfuric acid. The small amount of remaining aqueous in the mixing tank, the interface and any associated unseparated organic/aqueous mixture, and a small amount of organic phase are withdrawn to the extraction- wash interface pot.

(5) A stripping solution containing sulfuric acid (and op¬ tionally nickel sulfate from previous stripping contacts) is added to the mixing tank, along with the contents of the strip interface pot, and mixed for 5-15 minutes. To obtain good stripping of the organic phase (i.e., less than 0.5 g/L Ni, or preferably less than 0.1 g/L Ni) when high con¬ centrations of nickel (i.e., 50 g/L or more) are present in the stripping solution, the incoming strip solution should have a pH less than 1.2, and preferably less than 1.0. The separated aqueous solution is removed from the mixing tank and retained for the next stripping contact. If the pH has risen above the desired value, the solution is either acid- ified with additional sulfuric acid, or it is removed as final product and replaced with fresh sulfuric acid solu¬ tion. The small amount of remaining aqueous phase in the mixing tank, the interface and any associated unseparated organic/aqueous mixture, and a small amount of organic phase are withdrawn to the strip interface pot.

(6) Steps 1 through 5 are repeated.

It is especially important to limit the transfer of ammonia, since it will form a double salt, nickel ammonium sulfate, which has markedly lower solubility than nickel sulfate. Zinc contamination of the nickel sulfate is also undesirable because of its negative effects in certain plating operations. The extraction-wash prevents these and other impurities in the waste electroless nickel solution from accumulating in the product nickel sulfate solution. A wash following stripping is unnecessary in this appli¬ cation because the ammonia content of the adjusted feed provides sufficient buffer to absorb the small amount of acid transferred from stripping.

A preferred mode of operation for treatment of a waste chelated solution of copper, such as with the chelating agent EDTA, uses the following steps: (1) EDTA-containing feed solution, containing about 0.5 g/L copper, along with a portion of the aqueous solution from extraction-wash (step 4 below) from the previous cycle if the cycle in question is not the first, is adjusted to pH 11.5 to 12.2, preferably pH 11.8, with sodium hydroxide solution. (The amount of extraction-wash solution added depends on the number of extraction contacts done per cycle, adding an approximately equal portion to each ex¬ traction contact.) (2) The pH-adjusted feed solution is added, along with the contents of the extraction interface pot, to the mixing tank containing an organic solution of about 0.3 molar LIX™ 860 in kerosene, and mixed for 5 - 15 minutes. The sepa¬ rated aqueous phase, typically containing less than 1 ppm copper, is removed for disposal. (3) Step 2 may be repeated one or more times depending on the concentration of copper present in the extraction feed. After the last extraction raffinate is withdrawn, the small amount of remaining aqueous, the interface and any associ¬ ated unseparated organic/aqueous mixture, and a small amount of organic phase are withdrawn to the extraction interface pot.

(4) The retained aqueous solution from washing stripped organic, from step 7 as described below in the previous cycle if available, or in the first cycle a newly prepared aqueous solution of similar composition, is added to the loaded organic in the mixing box, along with the contents of the extraction-wash interface pot, and mixed for 5 - 15 minutes. The separated aqueous phase is withdrawn and re¬ tained for portionwise incorporation into the extraction contacts (step 1 & 2) of the following cycle. The small amount of remaining aqueous phase in the mixing tank, the interface, and any associated unseparated organic/aqueous mixture, and a small amount of organic phase are withdrawn to the extraction-wash interface pot. (5) Aqueous strip solution, optionally retained from the previous cycle, is added to the mixing box, along with the contents of the strip interface pot, and mixed for 5 - 15 minutes. To obtain removal of most of the copper from the LIX™ 860 organic phase, the concentration of the sulfuric acid in the strip solution should be in the range of 250 to 600 g/L, and preferably at least 300 to 400 g/L. After separation, the aqueous phase is withdrawn and retained for further stripping in a subsequent cycle. The small amount of remaining aqueous phase in the mixing tank, the interface and any associated unseparated organic/aqueous mixture, and a small amount of organic phase are withdrawn to the strip interface pot.

(6) Aqueous strip solution from step 5, containing at least 5 g/L, preferably at least 10 g/L, and more preferably at least 15 g/L, of copper, is continuously circulated through an electrowinning bath in which copper metal is deposited, and hydrogen ions and oxygen gas are generated. The cur¬ rent density is adjusted so the rate of copper plating is approximately equal to the rate of copper added by strip¬ ping.

(7) An aqueous salt solution, in which the anion of the salt is preferably sulfate, and the total ionic molarity is at least 0.05 molar, and preferably about 0.2 to 0.3 molar, along with the contents of the strip-wash interface pot, is added the mixer box, and mixed for 5 - 15 minutes. After separation, the aqueous phase is withdrawn and retained for use in the extraction-wash contact (step 3) of the fol¬ lowing cycle. The small amount of remaining aqueous phase in the mixing tank, the interface and any associated unsep¬ arated organic/aqueous mixture, and a small amount of or¬ ganic phase are withdrawn to the strip-wash interface pot. (8) Steps 1-7 are repeated.

Optionally, a portion of the strip solution may be bled to control build-up of impurities in the electrowin¬ ning electrolyte, and added to the aqueous feed in step 1 prior to (or during) pH adjustment. Since the electrowinning solution in the above de¬ scribed preferred method for use with EDTA-containing cop¬ per solutions is (in principle) continually recycled and never discarded, any deleterious components (such as chlor¬ ide) that reach the strip solution will build up with time and interfere with electrowinning performance. Accumula¬ tion of impurities transferred from the EDTA-copper feed solution via the organic cosolvent extraction phase is min¬ imized by use of the extraction-wash contact.

In addition, EDTA-copper solutions typically have very little buffering in the pH range above 10.5, which is the desired pH range for copper extraction. Thus a relatively small amount of acid transferred from stripping can de¬ crease the pH of the extraction aqueous to the point where copper extraction ceases, leading to incomplete extraction. Acid transfer is minimized by use of the strip-wash con¬ tact. Further, for the case of EDTA-copper extraction, the ability to maintain the aqueous pH within the range needed for complete extraction can be enhanced by adding a suit¬ able buffering agent to the EDTA-containing solution to be extracted before pH adjustment. A preferred buffer is phosphate/hydrogen phosphate, added at a preferred molar concentration ranging from 0.5 to 6 times the molar con¬ centration of copper, more preferably about 2 times.

The practice of the invention may be further appreci¬ ated by consideration of the following, non-limiting exa p- les and comparison examples.

Comparison Examples Group 1

This comparison example shows the pH dependence of the extraction of nickel from aqueous solutions not containing any chelating agent. Aqueous nickel sulfate feed solution was prepared to contain approximately 6 g/L Ni (from NiS0₄) and 0.1 M ammonium sulfate. The organic extractant was prepared by diluting LIX™ 860 (supplied as a kerosene so¬ lution of 5-dodecylsalicylaldoxime, commercially available from Henkel Corporation, Tucson, Arizona) with Escaid™ 110 (kerosene, commercially available from Exxon Corporation) to provide a 0.32 M solution of the oxime, which was ap¬ proximately three times the molar concentration of the nickel in the aqueous feed solution. The pH of the feed solution was initially adjusted to the basic side with NH^OH or to the acidic side with H₂S0₄ to give several adjusted feed solutions. The organic and aqueous phases were then combined in a 1:1 volume ratio at room temperature in glass bottles and shaken on a table shaker for 15 minutes. After separating and filtering the two phases, the aqueous equi¬ librium pH values were measured and the percent extraction determined by atomic absorption analysis of the organic and the aqueous layers. Results are given in Table 1. These data indicate that, with a pH_1/2 (i.e. , the pH at which half of the metal is extracted) of about 3.6, LIX™ 860 should give very high extraction of nickel at pH 4.5 or 5.

Table 1: NICKEL pH ISOTHERM

Equilibrium H: 2.41 2.60 3.37 3.53 3.70 3.73 % Extraction: 1.8 2.5 29.5 41 54.8 70.7

Examples and Comparison Examples Group 2 LIX™ 860 at 160 g/L in Escaid™ 110 was used in the same manner as in Comparison Example 1 to extract nickel from three different sources of spent electroless nickel plating bath solutions. The organic reagent was prepared as in Example 1 and its concentration represents three times the molar concentration of the nickel, i.e.. a 50% excess over the stoichiometric ratio, in the most nickel rich feed source, #2 in Table 2 below. Aqueous feed solu¬ tions were used at their existing pH as well as at two higher pH levels achieved by addition of concentrated am- monium hydroxide solution or sodium hydroxide solution. Equal volumes of organic and aqueous phases were combined in a bottle and shaken on a table shaker for 15 minutes at room temperature. The coalesced phases were separated and filtered to eliminate entrainment. The pH of the aqueous raffinates after extraction were observed to be substanti¬ ally the same as before extraction. The nickel concentra¬ tions of the aqueous raffinates and the initial feed solu- tions were determined by atomic absorption, and the results are given in Tables 2 and 3. These data show only partial removal of nickel when extracting at the natural pH (4.5-5) of the bath solutions, in contrast to the high extraction for uncomplexed nickel expected from the results shown in Example 1. To achieve high extraction of chelated nickel in a single extraction stage, the pH must be maintained within the range of 7 to 12.5, or preferably within the range of 8 to 12.

Adjunct Examples Group 3

LIX™ 860 at a concentration of 160 g/L in Escaid™ 110 was first loaded to about 8 g/L Ni by adjusting sample source #2 to pH 9 with NH₄OH, and contacting aqueous and organic phases in the manner generally described in Exam¬ ples Group 2. An aqueous strip solution containing 29.6 g/L Ni (from NiS0 ) and 7 g/L H₂S0₄, simulating a spent electrolyte from nickel electrowinning, was prepared. Strip aqueous and loaded organic solutions were combined in glass bottles in the ratios indicated in Table 4, and were mixed on a table shaker for 15 minutes. The coalesced phases were separated and the Ni concentrations determined by atomic absorption. The results are shown in Table 4. These data show that extracted nickel can be successfully stripped into a concentrated nickel solution as long as it contains sufficient excess acid.

Examples Group 4 These examples demonstrate some kinetics of an extrac¬ tion according to the invention. A stirred mixer box was used to contact electroless nickel spent bath solution and extractant. LIX™ 84 (supplied as a kerosene solution of 2- hydroxy-5-nonylacetophenone oxime, commercially available from Henkel Corporation, Tucson, Arizona) was diluted in Escaid™ 110 to a concentration of 170 g/L. The pH of aque- ous feed source #1 as in Table 2 was adjusted to 9.6 with concentrated NH₄OH. Equal volumes (100 mL each) of the or¬ ganic and aqueous feeds were added to a mixing box in the form of a right parallelepiped with rectangular faces and dimensions of 6.3 x 6.3 x 10.1 centimeters (hereinafter "cm") , which was equipped with an overhead stirrer with a 3.2 cm diameter agitator. The agitator was positioned at the interface and stirred at 2000 + 100 revolutions per minute. Aliquots (10 milliliters {hereinafter "ml"} each) were taken with a pipet at the times indicated in Table 5, the coalesced phases were separated and filtered, and the aqueous Ni concentration was determined by atomic absorp¬ tion. The results are shown in Table 5. These data show that LIX™ 84, a phenolic ketoxime, will extract virtually all the nickel from a spent electroless Ni bath solution within practical contact times.

Examples Group 5

These examples illustrate the extraction of copper from a spent electroless copper bath. 1. Preparation of extraction solutions and aqueous feed solutions

The solvent used in these extraction processes was Es¬ caid™ 110, an aliphatic kerosene. The complexing extract- ant, either LIX™-84, LIX™-860, LIX™-622 or LIX™-984, as noted, was used in the solvent at a concentration of 0.098 M. LIX™ 622 has the same composition as LIX™ 860 except it also contains approximately 17% tridecanol as modifier. LIX™ 984 is a 1:1 mixture of LIX™ 860 and LIX™ 84. The aqueous feed solution, from a spent electroless copper bath, contained 1.93 g/L Cu and had a pH of 11.1.

The aqueous stripping solution was either 150 g/L or 250 g/L sulfuric acid, as noted.

2. Procedure for extraction experiments (Table 6)

The organic extractant solution and the aqueous feed solution, in volume-to-volume ratios of organic to aqueous phases = 5/1, 1/1 and 1/5, were placed in a bottle and con¬ tacted via vigorous shaking for 1 hour. For each test, the phases were then allowed to sepa¬ rate. The aqueous phase was filtered, collected and ana¬ lyzed for Cu concentration by atomic absorption spectros- copy (AAS) , as the original feed solution had been. The results are shown in Table 6.

As shown by the data in Table 6, with the appropriate choice of conditions, essentially quantitative extraction of copper can be achieved.

3. Procedure for stripping experiments (Table 7)

The organic extractant solution (25 ml) was first loaded by vigorous shaking for 1 hour with the aqueous feed solution (25 ml) . The phases were then allowed to separate. Each aqueous phase was filtered, collected and analyzed for Cu concentration by atomic absorption spectroscopy (AAS) . Values for Cu concentrations in the loaded organic solu¬ tions were calculated from the AAS data for the aqueous samples.

The loaded organic solution (25 ml) and the aqueous stripping solutions (25 ml) were placed in a bottle and contacted via vigorous shaking for 1 hour. The phases were then allowed to separate. Each aqueous phase was filtered, collected and analyzed for Cu concentration by atomic ab¬ sorption spectroscopy (AAS) .

As illustrated in Table 7, upon contacting the loaded organic with aqueous sulfuric acid, the copper is trans¬ ferred into the aqueous phase.

These examples illustrate the effect of EDTA and QUAD- ROL™ on copper extraction. 1. Preparation of extraction solutions and aqueous feed solutions

The complexing extractant, LIX™-84 or LIX™-860, as noted below, was used in the solvent at a concentration of 0.1 M. Escaid™ 110, an aliphatic kerosene, was used as the solvent.

The aqueous feed solutions contained copper sulfate pentahydrate (0.05 M) and either (ethylenedinitrilo)-tetra- acetic acid disodium salt (Na-EDTA) or N,N,N' ,N*-tetrakis- (2-hydroxypropyl)-ethylenedia ine (QUADROL) , as noted, to give ratios of copper/chelating agent = 1/1 on a molar basis in deionized water. The EDTA feed solutions were pH adjusted, if needed, with 50% sodium hydroxide until the EDTA went into solution.

2. Procedure for pH Isotherm experiments (Tables 8-9) The aqueous feed solution was pH adjusted with either

50% sodium hydroxide or 150 g/L sulfuric acid to produce samples over a range of pH values.

The organic extractant solution (15 ml) and the aque- ous feed solutions (15 ml) were placed in a bottle and con¬ tacted via vigorous shaking for 1 hour.

For each test, the phases were allowed to separate. The aqueous raffinate was filtered, collected, tested for pH and analyzed for copper concentration by atomic absorp¬ tion spectroscopy (AAS) . It is generally known that, under the conditions of this experiment, in the absence of EDTA and other chelating agents, use of either LIX™-860 or LIX™- 84 would result in complete extraction of the copper in the range of pH 4 to 9. However, as shown in Table 8, in the presence of EDTA, only minimal extraction occurs in this pH range, while acceptable extraction can be achieved within the pH range of 11.5 - 13 with the ketoxime complexing agent in LIX™-84 and with the aldoxime complexing agent in LIX™860.

As shown in Table 9, in the presence of QUADROL , the pH must be maintained in the range of pH 6 to 11, or pref¬ erably within the range of 7 - 10, to achieve high recovery of the copper with LIX™-860 in a single extraction stage. With LIX™-84, the pH must be maintained in the range of pH 6 to 9.5 to achieve high recovery of the copper in a single extraction stage.

Although as indicated above, the basic extraction and/or recovery processes as illustrated above are preferably divided into multiple stages in a manner well known in the art, the present inventors recognized that prior systems for accomplishing this have inherent efficiency and cross contamination problems. As a result, the present inventors designed a system or apparatus, as described and illustrated below in its various embodiments, to overcome the problems in the prior art. Note that although for purposes of illustration, the embodiments are shown and described for extracting nickel from spent electroless nickel solution, and for extracting copper from ethylene diamine tetraacetic acid (EDTA) copper solution, respectively, the apparatus or systems illustrated are not meant to be so limited.

The present apparatus or systems are suitable for use with any batch solvent extraction process in which the organic solvent is less dense than water. Although the apparatus illustrated below includes at least one wash tank in one embodiment, and two wash tanks in another embodiment, for providing one or two wash cycles, respectively, other batch solvent applications may not require any wash cycles, and the illustrated wash tanks incorporated in the systems below can then be eliminated.

With reference to Figs. 1 and 2, apparatus is shown for inclusion in a system for extracting nickel from a spent electroless nickel solution, in this example. The apparatus includes a feed tank Tl, mixing tank T2, raffinate holding tank T3, first wash tank T4, and a regenerant acid tank T5. A pump 2 is connected in series with a filter 3 between a source of spent electroless nickel solution 4 and feed tank Tl. A pump 6 is connected between a source of ammonium hydroxide 8, in this example, and feed tank Tl. A motor 10 is attached to the top of feed tank Tl for turning a drive shaft 12 connected at a lower end to a mixer blade 14. Level sensors 16, 17, and 18 are located at predetermined heights in tank Tl, as shown, for providing level signals LSI, LS2, and LS3, respectively. These level signals LSI through LS3 are individually produced by level sensors 16 through 18, respectively, whenever the fluid in tank Tl is at least at the height of the associated sensor. Similarly, level sensors 20-23 are positioned at different heights in tank T4, level sensor 24 at a predetermined maximum height in tank T2, and level sensors 26 and 27 at respective maximum and minimum predetermined fluid heights in regenerant acid tank T5, for producing level signals LS4 through LS10, respectively, when the level of fluid in an associated tank attains or exceeds the level of the associated sensor, respectively. Note that as an alternative, these level sensors 16 through 18, 20 through 24, and 26 and 27, can be substituted by use of a single level sensor in each tank that provides for producing a signal indicative of the actual height of fluid in an associated tank at any given time, instead of indicating the fluid height has attained a certain predetermined level at which level a level sensor is mounted, as in this example. pH sensors 28, 29, and 30 are located near the bottoms of tanks Tl, T4, and T5, respectively, for providing signals pHl, pH2, and pH3, respectively, indicative of the pH of the fluid in tanks Tl, T2, and T5, respectively.

A pump 32 is connected between tank T4 and a source of sulfuric acid 34. Another pump 36 is connected between tank T4 and a source of acetic acid 38, in this example. A motor 40 is connected to the top of tank T4 for driving a drive shaft 42 connected at one end to a mixer blade 44. A pump 33 is connected between a source of water 37 and tank T4. In certain applications, the water 37 may be deionized water (D.I.).

A mixer motor 46 is connected to the top of tank T2, for rotating a drive shaft 46, the end of which is connected to an impeller 48. Another motor 50 is connected to the top of tank T5, for rotating a drive shaft 51, the end of which is connected to a mixer blade 52.

A pump 54 is connected from tank Tl through an in line filter 3, check valve 56, and check valve 58, for pumping fluid from tank Tl to tank T2. A pump 60 is connected between tank T4, for pumping spent wash fluid from tank T4 to a point of waste treatment or a sewer. Another pump 62 is connected between a drain port 64 (at the bottom of tank T2) and tank T4, for pumping fluid from tank T2 to tank T4. Another pump 66 is connected between drain port 64 and a raffinate holding tank T3, for pumping fluid from tank T2 to tank T3. A pump 68 is connected in series with a filter 3, check valve 56, and a check valve 58, the latter being located near the bottom of tank T2. Pump 68 is operable for pumping fluid from tank T4 to tank T2. A pump 70 is connected through a check valve 56 in series with a check valve 58 (in tank T2) for pumping fluid from tank T5 to tank T2. Another pump 72 is connected between the drain port 64 of tank T2 and tank T5, and is operable for pumping fluid from tank T2 to tank T5. A pump 74 is connected from tank T5 to a product holding tank T6, and is operable for pumping fluid from tank T5 to tank T6. A pump 75 is connected between the source of sulfuric acid 34 and tank T5, and is operable for pumping sulfuric acid from source 34 to tank T5. A pump 49 is connected between tank T5 and a source of water 37, for pumping water into tank T5.

The check valves 56 and 58 are each diaphragm check valves manufactured by RH Plast-O-Matic, as used in an engineering prototype of the system. However, for check valves 58, which typically are immersed in the fluid in tank Tl, the bottom threaded coupling portions of these valves are machined off to avoid any entrapment of fluid in these portions to promote fluid mixing and eliminate dead spots.

A fluid phase detector, in this example an optical sensor 76, is connected to the drain port 64 for providing a fluid phase signal 78. When the fluid in drain port 64 changes from a clear fluid toward one that is more opaque with less light transmission therethrough, the magnitude of fluid phase signal 78 changes. Such magnitude changes provide a measurable indication of the fluid phase in drain port 64 at any given time.

Three interface tanks or pots 80, 82, and 84, respectively, are included as shown. A source of pressurized air is connected via an air line 86 to inlet ports of control valves 88, 90, and 92, respectively, the valves having outlet ports connected to interface tanks 82, 80, and 84, respectively. Control valves 94, 96, and 98 have inlet ports connected to interface tanks 82, 80, and 84, respectively, and are individually operable for serving as pressure relief valves for their associated interface tanks. With reference to Figs. 2 and 3, interface tanks or pots 82, 80, and 84, are connected to outlet ports of control valves 100, 102, and 104, respectively. The inlet ports of control valves 100, 102, and 104 are coupled to drain port 64 of mixing tank T2. This coupling is carried out in a unique manner, that provides a preferred embodiment of the invention. More specifically, Fig. 3 shows a detailed view 106 of connections providing the "coupling" to drain port 64 of tank T2. Control valves 108, 110, and 112, modified as described in detail below, have respective input ports or inlet ports connected to drain port 64. An outlet port of control valve 108 is connected to an input port of pump 66. An outlet port of control valve 110 is connected to an input port of pump 62. An outlet or output port of control valve 112 is connected to an input port of pump 72. The modified control valves 108, 110, and 112 each have inlet port drain lines 114, 116, and 118, respectively, connected to inlet ports 120, 122, and 124, respectively, of a manifold 126. Outlet ports 128, 130, and 132, of manifold 126, are connected via fluid lines 134, 136, and 138, to the inlet ports of control valves 100, 104, and 102, respectively.

The typical air operated fluid control valves used in this example are configured as shown for valve 140 in Fig. 4. This valve is a miniature diaphragm valve part No. 5400-0-10, manufactured by Plast-O-Matic. In this example, normal valve configuration 140 is used for providing control valves 88, 90, 92, 94, 96, 98, 100, 102, and 104. However, as previously indicated, control valve 140 must be modified to the valve configuration 142 as shown in Fig. 5, for providing modified control valves 108, 110, and 112. The difference is that the normal valve configuration 140 does not provide any means for cleaning out or draining its liquid inlet region. After the valve is operated, residual liquid remains in the liquid inlet region that might cause cross-contamination with common fluid paths in the system in later processing. To overcome this problem, the present inventors modified the valve configuration 140 to provide the configuration 142 shown in Fig. 5. As shown, the modification for valve configuration 142 provides for including a hole 144 at the bottom of the liquid inlet region of modified valve 142, for providing a cleanout drain for draining fluid from the liquid inlet region to an associated one of the interface tanks 80, 82, and 84, in this example. The modified valve configuration 142, as used for providing control valves 108, 110, and 112, in this example, substantially eliminates cross contamination in a manner described below.

A controller 146 is programmed for providing automatic operation of the batch extraction system of Fig. 2. The controller 146 can be provided by a programmable logic device, a microprocessor, or even a small dedicated computer. Controller 146 provides at programmed times control signals for individually driving a bank of solenoid operated valves 148. These valves (not shown) individually operate to pass pressurized air from a common pressurized air line 150 as individual air pressure control signals U, V, W, X, Y, Z, AA, BB, CC, to valves 94, 96, 98, 100, 102, 104, 108, 110, and 112, respectively for opening the associated valve

Controller 146 also provides at programmed times electrical control signals R, S, and T, respectively, for operating solenoid valves 88, 90, and 92, respectively, to open for passing pressurized air into interface tanks 82, 80, and 84, respectively, for purging liquid from these tanks, as will be described below. Controller 146 also provides at programmed times individual control signals A, B, D, E, I, J, K, L, M, N, 0, P, Q, HH, and II, to pumps 2, 6, 32, 36, 54, 60, 62, 66, 68, 70, 72, 74, 75, 33, and 49, respectively, for individually operating these pumps. Controller 146 is further programmed for providing control signals C, F, G, and H, for turning on mixer motors 10, 40, 46, and 50, respectively. Controller 146 also monitors liquid level signals LSI through LS10, and pH signals pHl, pH2, and pH3, for operating the pumps, valves, and motors of the present system in a programmed manner, as will be described.

Pumps 2, 6, 32, 33, 34, 36, 60, and 75 are diaphragm metering pumps, in this example. Pumps 54, 62, 68, 66, 70, 72, and 74 are centrifugal pumps, in this example.

Note further that mixing tank T2 includes a screen 59 across the bottom of the tank above the drain port 64. Screen 59 is of a mesh size to substantially accelerate the completion of coalescence of organic/aqueous mixture. During system operation, the area above drain port 64 sometimes becomes filled with "rag", a network of organic films enclosing small zones or globules of aqueous. The mild mechanical stress caused by passing the "rag" through the screen 59 tends to coalesce the rag to a very narrow band of emulsion that is easily transferred to an interface pot 80, 82, or 84, as described below.

The design of the impeller 48 is shown in Figs. 6 and 7. A drive shaft 47 is connected to a central hub 170 of a disk-shaped blade carrier 172. Mixing blades 174 are mounted about the circumference of the blade carrier 172, and equally spaced from one another. In this example, six mixing blades 174 are spaced 60° from one another, as shown.

With further reference to Fig. 1, the generalized logic flow is shown. After adjusting the pH of the spent electroless nickel solution, in this example, it is transferred to mixing tank T2 for mixing with an organic solvent, for extracting the nickel from the feed solution to the organic solvent. Details for the organic solvent, and other chemicals used in the system, are given above with regard to the chemical processing previously described. After extraction is completed, a quiescent time is provided for permitting the aqueous phase depleted of nickel and the organic phase with nickel to break apart from an emulsion therebetween, whereafter the aqueous phase is transferred from tank T2 to a raffinate tank T3, for later waste processing or discharge. The remaining organic phase in tank T2 is then washed with a wash solution transferred from tank T4 into tank T2, for removing contaminants from and neutralizing the organic phase. In this example, the alkalinity of the organic phase is neutralized and co-extracted metals such as zinc are removed. Another important purpose of washing is the removal of aqueous from the previous operation that never left T2 (because of entrainment, hangup on the walls, and so forth) ; effectively the wash aqueous dilutes that aqueous (with its impurities) and removes it when the aqueous wash is drained.

After the washing cycle is completed, the used wash solution is transferred from tank T2 back to tank T4. The washed organic phase iε then regenerated via the transfer of regenerant acid, in this example, from tank T5 to tank T2, for causing the nickel in the organic phase to be transferred to the regenerant acid, sulfuric acid in this example. After the recovery cycle or regeneration of the organic solvent, the used acid is removed from tank T2, and transferred back to tank T5 for reuεe, until such time that the pH of the acid exceeds a predetermined value. The batch processing has been completed for a batch of spent electroless nickel solution. The system is now ready for receiving another batch of spent electrolesε nickel solution from source 4 or feed tank Tl, for processing. Details of each cycle of operation will now be given.

With further reference to Figs. 1 through 3, operation of various embodiments of the invention for extracting nickel from spent electroless nickel solution will now be described in detail. In this example, a source of spent electroless nickel solution 4 is delivered for batch processing via a pump 2 to feed tank Tl. Controller 146 is programmed to sense the level sense signals LSI through LS3 to determine if the spent electroless nickel solution presently in tank Tl is at or above the level of a predetermined one of the level sensors 16, 17, and 18. In this example, the desired level is that of level sensor 17. To initiate the first processing operation for adjusting the pH of the electroless nickel feed solution in tank Tl, controller 146 is programmed to first determine whether sufficient spent electroless nickel solution 4 is contained within tank Tl. To accomplish this, level signal LS2 is sensed, and if this signal is at +5 volts, in this example, indicating that the level of fluid in tank Tl is at the proper level, controller 146 proceeds to generate control signal C for turning on motor 10, for causing mixer blade 14 to rotate for mixing the fluid in tank Tl. However, if LS2 is at 0 volt, controller 146 generates control signal A for turning on pump 2, for causing additional spent electroless nickel solution to be transferred from a source 4 thereof through pump 2, and filter 3, to tank Tl. Note that level sensor 16 for changing level signal LSI from zero volt to +5 volt when fluid in Tl reaches the level of level sensor 16, is a fail safe sensor, whereby controller 146 is programmed to turn off or inhibit operation of pumps 2 and/or 6 if the fluid level attains the level of level sensor 16. In this manner, overflow of fluid from tank Tl is prevented.

When level signal LS2 changes state from 0 volt to +5 volts, for example, controller 146 terminates control signal A for turning off pump 2. Immediately thereafter control signal C is generated for turning on motor 10, for rotating mixer blade 14, as previously described. Controller 146 responds to pH signal pHl being less than a predetermined value, for generating control signal B, for turning on diaphragm pump 6, in this example, for transferring an alkaline solution from a source 8 thereof, ammonium hydroxide in this example, into tank Tl until the signal pHl attains a predetermined value showing that the pH of the solution in tank Tl has been adjusted to a predetermined value. During this pH adjustment period, controller 146 also generates control signal C for energizing motor 10, to rotate mixer blade 14 for ensuring thorough mixing of the ammonium hydroxide with the spent electroless nickel solution. After the proper pH is attained, control signal B is terminated, for turning off pump 6, but motor 10 is continuously energized for another preset period of time, five minutes in this example, during which time the pH in tank Tl is monitored. If the pH reduces again to below the predetermined set point, controller 146 again generates control signal B, for turning on pump 6, for feeding additional ammonium hydroxide into feed tank Tl. This cycle of operation is repeated until the pH stays at the predetermined set point level for at least a predetermined period of time, five minutes in this example. After attaining the proper pH level, controller 146 terminates control signal C for turning off motor 10. Next, controller 146 senses the state of level signal LS8, and if this signal iε at +5 volts, in this example, indicative of no further pH adjusted electroless nickel solution being required for batch processing in mixing tank T2, controller 146 proceeds to enter into an extraction cycle of operation. However, if level signal LS8 is at 0 volt, indicating additional pH adjuεted electroless nickel solution must be added to mixing tank T2, controller 146 generates pump control signal "I" for turning on pump 54 to transfer fluid from tank Tl to tank T2. On senεing that the εtate of level εignal LS8 changeε to +5 volts, controller 146 terminates pump control signal "I", and enters into the programming routine for an extraction cycle of operation.

After controller 146 has operated pump 54 for a sufficient period of time to fill tank T2 to a predetermined level, control signal I is terminated, and the fluid in mixing tank T2 is provided a predetermined quiescent time period for permitting any emulsions therein to break up. After that time, control signal G is generated for turning on motor 46 to rotate impeller 48 for a predetermined time to mix the organic solvent with the pH adjusted electroless nickel solution. Also, after mixing has begun, controller 146 generates control signal S for turning on valve 90 (for one minute in this example) , causing pressurized air to enter interface tank 80, for forcing raffinate fluid from interface tank or pot 80 into mixing tank T2 for addition to the batch of spent electroless nickel solution undergoing nickel extraction. After a mixing time of 15 minutes, in this example, control signal G is terminated, and another quiescent period of time is provided for permitting an emulεion formed in tank T2 to coalesce. In this example, the quiescent time is 15 minuteε. Controller 146 εenεes the condition of fluid phase signal 78 from optical sensor 76, to determine whether a clear liquid phase resides in drain port 64. If not, an additional quiescent time is provided. Next when fluid phase signal 78 signals a clear liquid phase, controller 146 generates control signals V and Y for opening valves 96 and 102, respectively, for a predetermined period of time, for drawing aqueous feed solution from drain port 64, through inlet portions of control valves 108, 110, and 112, through manifold 126, through valve 102, into raffinate pot 80, whereafter control signals V and Y are terminated, for closing valves 96 and 102, respectively. Control signals AA and L are next generated, for turning on raffinate drain valve 108 and pump 66, respectively, to transfer raffinate from tank T2 via itε drain port 64 to raffinate holding tank T3. Note that raffinate is the name given to the aqueous feed solution after it has been extracted. Raffinate collected in tank T3 is later discharged or tranεferred to a waste treatment facility, or to a site for further processing. When fluid phase signal 78 changes value to show that a fluid interface has paεεed through drain port 64, that iε organic phase haε reached drain port 64, controller 146 terminates raffinate control valve signal AA, for closing valve 108, and terminates pump signal L for turning off pump 66. The extraction cycle is continued by controller 146 generating control signal Y for opening control valve 102 for a predetermined period of time, one minute in this example, for again draining fluid from drain port 64 through the inlet portions of control valves 108, 110, and 112, manifold 126, into raffinate interface pot 80, whereafter control signal Y is terminated to close control valve 102. A common fluid composition now exists between the organic phase in tank T2, the fluid in drain port 64, and in the common fluid paths between this drain port 64 and the inlet portions of control valves 108, 110, 112, through to the input port of control valve 102. As previously explained, in this manner, cross-contamination by residual fluids from the extraction cycle of operation contaminating fluids involved in the next cycle of operation is substantially eliminated. Continuing in this extraction cycle, controller 146 is programmed to next increase an extraction counter by one count. If the extraction counter has not reached a predetermined count limit, the aforesaid extraction cycle steps are repeated in an iterative fashion until the extraction counter counts up to the predetermined limit, whereafter controller 146 then enters the εystem into a wash cycle. Note that the extraction counter is not shown in the drawings, in that it is a software based counter provided via the programming of controller 146, aε would be known to one of εkill in the art. Programming for the wash cycle of operation will now be described in detail.

Before the wash cycle is initiated, controller 146 is programmed to determine whether the wash solution in wash tank T4 is ready for transfer to tank T2. First, if level signal LS5 is not indicative of the level of fluid or liquid in tank T4 being at or above the level of senεor 21 (in this example, LS5 would then be at +5 volts) , valve control signal HH iε generated for operating diaphragm metering pump 33, to pump DI water from εource 37 into wash tank T4, until LS5 changes state from 0 volt to +5 volts, whereafter the pump signal HH is terminated for turning off pump 33. Control signal E is generated for turning on diaphragm metering pump 36 to add a predetermined amount of acetic acid from source 38, for buffering the wash solution as required. Note that level senεor 20 is a fail safe sensor, whereby if associated level signal LS4 changes state from zero to +5 volts, controller 146 is programmed to respond by turning and/or inhibiting operation of pumpε 32, 33, 36, and 62. In this manner, overflow of fluid from tank T4 is prevented. If the value of pH2 εignal iε at a predetermined value indicative of the waεh εolution in tank T4 being at a predetermined pH, no further action will be taken. However, if the pH iε not at or below the predetermined value, control εignal F iε generated for turning on mixer motor 40, followed by generating control εignal D for turning on diaphragm metering pump 32 to pump εulfuric acid from εulfuric acid εource 34 into tank T4. When the pH in the waεh εolution attainε a predetermined value, control signal F is terminated for turning off mixer motor 40. Once controller 146 haε determined through εensing level signal LS5, and pH signal pH2 that the wash solution in tank T4 iε ready for tranεfer to mixing tank T2, provided that level εignal LS8 iε at 0 volt, in thiε example, indicative that the level of fluid in mixing tank T2 has not attained the height of level sensor 24, control signal M is generated for turning on pump 68, for tranεferring wash solution from tank T4 to tank T2. When the level of liquid in mixing tank T2 attains the height of senεor 24 (level εignal LS8 changes state from 0 volt to +5 volts) , controller 146 respondε by terminating control εignal M, for turning off pump 68. The programmed quieεcent time iε entered into, for one to two minuteε in this example, to permit breakup of emulsion in tank T2.

After this quiescent period, control signal G is generated for turning on mixer motor 46, for mixing together the wash solution and organic phase in tank T2, for a predetermined period of time. Also at this time, control signal T is generated for turning on solenoid valve 92, to cauεe preεεurized air to enter waεh interface pot 84, forcing any fluid therein to be transferred into mixing tank T2. In this example, control signal T is generated for a one minute time period, and thereafter terminated. In this example, the mixing time iε 15 minuteε, whereafter control εignal G is terminated, for turning off motor 46. Another quiescent period of predetermined duration is then provided. In this example, a fifteen minute quiescent time is provided for permitting any emulsion to coalesce in tank T2. When fluid phase signal 78 signals a clear liquid phase, controller 146 generates control signals W and Z for opening valves 98 and 104, respectively, for a predetermined period of time, for drawing wash solution from drain port 64, through inlet portions of control valves 108, 110, and 112, through manifold 126, through valve 104, into waεh pot 104, whereafter control εignals W and Z are terminated, for closing valves 98 and 104, respectively. Thereafter, valve control signal BB is generated for opening modified control valve 110, and control signal K is generated for turning on pump 62 to transfer used wash water from tank 2 back to tank 4, for reuse. In certain applications, when used wash solution iε transferred from mixing tank T2 back to wash tank T4, it may be required that controller 146 be programmed for generating control signal J to operate pump 60 for transferring a εubεtantial portion of the used wash solution to waste treatment.

The transfer of used wash solution from tank T2 back to wash tank T4 is completed upon controller 146 sensing a change in state of fluid phase signalε 78 from optical sensor 76, for terminating control signal K to turn off pump 62. Next, control signal Z is generated for turning on control valve 104, control signal W iε generated for turning on control valve 98 for preεεure relieving tank 84, for draining fluid tank T2, through drain port 64, through the inlet portions of control valves 108, 110, 112, through manifold 126, and through valve 104 into wash interface pot 84. After a predetermined time, one minute in this example, control signalε W and Z are terminated for cloεing valveε 98 and 104, for terminating the drainage. Note that similarly, whenever control signal Y is generated for opening control valve 102, controller 146 is programmed to alεo generate control εignal V for opening preεsure relief valve 96, and whenever control signal X iε generated for opening control valve 100, control εignal U iε alεo generated for opening control valve 94 for pressure relieving interface pot 82.

Controller 146 is programmed to now enter into a recovery cycle of operation. In this example, controller 146 iε programmed to insure that the regenerant acid in tank T5 is at a proper pH and level, before the recovery cycle is actually initiated. First, the state of liquid level εignal LS9 iε monitored to determine whether the regenerant acid in tank T5 iε at or above the level of level εenεor 26. If LS9 iε at +5 voltε, for example, controller 146 will proceed to insure that the pH is at the proper level. However, if LS9 is at 0 volt, control signal II is generated for operating diaphragm metering pump 49 to deliver water from a source 37 into tank T5. When the state of level signal LS9 changes from 0 volt to +5 volts, pump signal II is terminated, for turning off pump 49. Thereafter, the value of pH3 signal is sensed to determine if the pH of the regenerant acid solution in tank T5 is below or at a predetermined value. If the answer is yes, controller 146 is programmed to proceed to the recovery cycle as described below. If the answer is no, controller 146 iε programmed to determine whether a εoftware baεed acid addition counter haε reached a predetermined count limit. In the event of determining that the acid addition counter had not reached its count limit, controller 146 is programmed to generate control εignal H, for turning on mixer motor 50. In the next εtep, control εignal Q is generated for turning on diaphragm metering pump 75 for a predetermined period of time, for transferring a predetermined amount of concentrated sulfuric acid from tank 34 into regenerant acid tank T5. The software baεed acid addition counter iε increased in count by one count. The value of pH3 is again senεed, and if the pH of the regenerant acid in tank T5 iε εtill above the predetermined value, another predetermined amount of acid is added as previously indicated. This cycling is repeated until the pH is at or below the predetermined value as indicated by senεing pH3. Thereafter, control signal H is terminated, for turning off mixer motor 50. Controller 146 is programmed to now begin the actual recovery cycle.

In initiating the recovery cycle, controller 146 senεeε whether the liquid in mixing tank T2 iε at the level of level εensor 24, as indicated by level signal LS8 being at +5 volts, for example. Typically at thiε time, the level of liquid in mixing tank T2 εhould be substantially below the level of level senεor 24, causing level signal LS8 to be at 0 volt. If this is the case, controller 146 is programmed to generate pump controller drive signal N, provided that the acid in tank T5 is ready for transfer, for turning on pump 70 to transfer regenerant acid from tank T5 to mixing tank T2. When controller 146 εenεeε that liquid level εignal LS8 changes state to +5 volts, pump drive signal N iε terminated for turning off pump 70. Control signal R is generated for one minute, in this example, for opening valve 88 to transfer the contents of acid pot 82 into tank T2. Drive signal G is generated, for turning on mixer motor 46 for a predetermined period of time, after which signal G is terminated. A programmed quiescent time, 15 minutes in this example, is entered into for permitting emulsion to break up in mixing tank T2. Next, when fluid phaεe εignal 78 εignalε a clear liquid phaεe, controller 146 generates control signalε U and X for opening valveε 94 and 100, reεpectively, for a predetermined period of time, for drawing aqueouε feed solution from drain port 64, through inlet portions of control valveε 108, 110, and 112, through manifold 126 through valve 100, into acid pot 82, whereafter control signals U and X are terminated, for closing valves 94 and 100, respectively. After this pre-drain operation, control signal CC iε generated for opening acid drain valve 112, and pump drive εignal "0" iε generated for turning on pump 72 to tranεfer uεed acid from mixing tank T2 back to acid tank T5. When a fluid interface iε detected by controller 146 εenεing a change in state of fluid phase signal 78, acid drain control valve signal CC is terminated for closing this valve, and pump control signal "O" is terminated for turning off pump 72.

Next, valve control signal X is generated for opening valve 100, and valve control signal U iε generated for opening preεεure relief valve 94, all for draining fluid from tank T2 through drain port 64, through the inlet portionε of modified control valveε 108, 110, and 112, and through valve 100 into acid interface pot 82, for inεuring that any potential cross-contaminating fluids are purged from the asεociated common fluid lineε or paths. Control signals X and U are generated for a predetermined period of time, one minute in this example, after which these signals are terminated.

If it is determined above that the software based acid addition counter has reached a predetermined count limit, a special "partial strip" cycle is initiated. First, the recovery cycle described above iε initiated and completed. Immediately after used acid being returned from T2 to T5, controller 146 generates signal P for turning on pump 74 to transfer the spent acid from tank T5 to tank T6. After senεing level signal LS10 changing state from +5 volt to zero volt, in thiε example, controller 146 terminateε pump drive signal P. Controller 146 is programmed to generate motor drive signal H for turning on mixer motor 50, signal Q for turning on pump 75, and signal II for turning on pump 49, to add water and acid (at predetermined times) to tank T5 as appropriate, while senεing level signal LS9 and pH3, to restore the level of acid at a proper pH in tank T5 aε indicated in detail above. Thereafter, a normal recovery cycle iε initiated, aε described above.

Controller 146 then senεeε the value of εignal pH3 for determining whether the pH of the acid in tank T5 is at or below a predetermined εet point. If it iε, controller 46 enterε into the next extraction cycle. If the pH is above the predetermined set point at this time, controller 146 then operates pump 75 for adding acid as indicated above. Note that the nickel sulphate collected in the product holding tank T6 is transferred from this tank for use or further processing.

As shown in Figs. 8 through 10, in another embodiment of the invention, the system is expanded to include a second wash tank, and additional programmed processing steps, for extracting copper from a chelated copper εolution, εuch aε the chelating agent EDTA. With reference to the process control logic flow diagram of Fig. 8, relative to the embodiment of the invention described above, this embodiment includes the addition of a second wash tank T7, and in the preferred embodiment electrowinning apparatus (not shown) coupled to tank T6. As in the syεtem configuration for processing nickel, prior to the extraction cycle, the EDTA copper solution for procesεing iε tranεferred to tank Tl for pH adjustment. After the pH of the solution is adjusted, it is transferred to the mixing tank T2 for mixing with the organic solvent, as described above. After a quiescent period, raffinate iε drawn off and collected in a holding tank T3, as before. A wash solution is then transferred from tank T4 to mixing tank T2 for washing the organic phase to remove contaminants, and neutralize the alkalinity. The used wash εolution iε tranεferred back to waεh tank T4, and in certain applicationε iε tranεferred in portionε from tank T4 to tank Tl, for blending with incoming aqueouε feed. A εecond waεh tank T7 iε added for washing the organic solvent after regeneration thereof, for removing contaminants and acidity from the organic solvent. Under appropriate conditions, assuming that the pH of the used second wash solution is within a predetermined range, it is tranεferred from mixing tank T2 to the first wash tank T4, for use aε a portion of the firεt waεh εolution in the next first wash cycle, that iε the extraction waεh cycle. Alεo, conventional electrowinning apparatuε can be aεsociated with product recovery tank T6, for permitting copper to be directly plated out of spent acid pumped into tank T6 from the regenerant acid tank T5. The copper that is plated out can then be removed from tank T6 for reuse. Also, the acid that is formed as the copper is plated out via the electrowinning apparatus is in effect regenerated, and iε pumped back into acid tank T5 for reuεe in the εyεtem as a regenerating agent. If electrowinning is used, regenerant is continuously pumped between tanks T5 and T6. If electrowinning is not uεed, the copper laden acid can be proceεεed off site for removal of the copper.

Note in the procesε control logic flow diagram that a εmall bleed εtream iε εhown by fluid path 172, for bleeding off a εmall amount of acid laden with copper from tank T6 to the feed tank Tl. The purpoεe of thiε iε to reduce the buildup of contaminantε, εuch aε chloride in the acid εolution in acid tank T5. In other words, masε balancing is provided through this small bleed εtream mechaniεm, to reduce the level of contaminantε in the acid. This fluidic bleed εtream is provided in the syεtem of Fig. 9 via diaphragm metering pump 154 being operable for pumping a εmall amount of copper laden acid from tank T6 to the feed tank Tl, as shown.

With further reference to Fig. 9, the EDTA copper proceεεing iε εubεtantially εimilar to the proceεεing of εpent electroless nickel solution, as previously described, relative to the system or apparatus. The programming of controller 146 is as a result substantially similar, particularly for the pH adjustment in feed tank Tl. One difference is that the feed pump 2 is used for pumping EDTA copper εolution from a εource 4¹ thereof into tank Tl, inεtead of pumping electroleεε nickel. Alεo, in thiε example, the alkaline εolution added to Tl for pH adjuεtment is sodium hydroxide from a source 8* thereof, rather than ammonium hydroxide from a source 8, as in processing the electrolesε nickel. Otherwise, the pH adjustment is carried out in substantially the same manner. Similarly, the extraction cycle, first wash cycle, and regeneration cycles, are all carried out in substantially the same manner as previously described for the above example of extracting nickel from spent electroless nickel solutionε.

When uεing sulfuric acid to strip copper and build up a copper sulfate solution, the regeneration cycle is quite similar to that of nickel. However, the regeneration cycle is significantly different when using electrowinning. No acid addition counter is used, since the copper sulfate solution is never "finished", but rather iε continuously treated by electrowinning to plate out copper and regenerate acid.

The major differences between the expanded system of Fig. 9, relative to the syεtem of Fig. 2 now follows. After the recovery cycle or regeneration of the organic solvent cycle of operation, it is important in the EDTA copper procesεing to both remove contaminantε, and neutralize the remaining acidic component of the organic εolvent reεulting from the recovery or regeneration cycle. To accompliεh thiε, the second wash tank, T7, has been added to the system. Also, level sensors 158 through 161 have been included at different heights in wash tank T7, and a pH sensor 162 is mounted near the bottom of tank T7, for producing level signalε LS11 through LS14, and pH signal pH4, respectively. A motor 157 is mounted on the top of tank T7, and is energized by a control signal JJ for turning a drive shaft 174 to rotate a mixer blade 176. A pump 165 driven by a controller drive signal KK is connected between tank T7 and mixing tank T2, for pumping fluid from T7, through a filter 3, and check valves 56 and 58, to T2. Another pump 178 driven by a drive signal LL is connected between drain port 64 of tank T2 and tank T7, for pumping fluid from tank T2 to tank T7. During the extraction wash cycle, used second wash solution from a previous cycle is pumped by pump 165 to tank T2. After completing washing of the organic phaεe in tank T2, controller 146 iε programmed to turn on pump 62 via drive εignal K, for tranεferring the uεed firεt waεh εolution back to tank T4. Portionε of the uεed firεt waεh εolution are then pumped by pump 190 (driven by εignal QQ) from tank T4 to feed tank Tl. Thiε iε different than the εyεtem of Fig. 2 for proceεεing spent electrolesε nickel, in that portionε of the uεed firεt waεh solution are pumped to waste treatment.

In the system of Figs. 8 and 9, after the organic solvent has been recovered or regenerated, and used acid returned to tank T5, as in the system configuration of Fig. 2, a second wash cycle is entered into. Controller 146 is programmed to senεe level εignalε LS11 through LS14, and pH εignal pH4, for turning on pump 156 via εignal FF, and mixer motor 157 via control signal JJ, as necessary to attain the proper level of fluid in tank T7, and adjuεt the sodium εulphate therein. Note that the εodium εulfate helpε maintain good phaεe diεengagement rateε. In thiε regard, water from a εource 37 thereof is supplied by controller 146 generating a pumping signal MM for operating a diaphragm metering pump 180 to add DI water to tank T7 as necesεary, along with εodium εulphate εolution, to obtain the proper second wash solution. After the appropriate fluid level, in this example, when LS11 iε at +5 voltε, controller 146 iε programmed to turn off motor 157, and initiate the εecond wash cycle after used acid has been transferred from mixing tank T2 back to the acid tank T5, as previously described.

The second wash cycle is entered into by controller 146 turning on pump 165 via generation of drive signal KK, to transfer second waεh solution from tank T7 into mixing tank T2, until the level of fluid within the mixing tank attains a predetermined level detected by level εignal LS8 going to +5 voltε, in thiε example. At that time, control or motor drive εignal KK iε terminated, for turning off pump 165. Mixer motor 46 iε energized via drive signal G, for mixing the fluid in tank T2 for a predetermined period of time, 15 minutes in this example, after which control signal G is terminated for turning off motor 46. Also at this time, controller 146 generates control signal PP for opening valve 186 to cause pressurized air to be forced into second waεh interface pot 151, in turn forcing fluid therefrom into mixing tank T2. Thiε purging operation iε continued for a predetermined period of time, one minute in thiε example, whereafter control εignal PP iε terminated for cloεing valve 186.

A quieεcent period iε entered into to permit emulεionε to coaleεce, the quieεcent time typically being 15 minuteε, in thiε example. Next, when fluid phaεe εignal 78 εignals a clear liquid phase, controller 146 generates control signals NN and 00 for opening valves 182 and 184, respectively, for a predetermined period of time, for drawing aqueous feed εolution from drain port 64, through inlet portionε of control valveε 108, 110, and 112, through manifold 126, through valve 182, into second waεh pot 151, whereafter control εignalε NN and 00 are terminated, for cloεing valveε 182 and 184, respectively. After this pre- drain operation, controller 146 generateε εignal GG for opening another modified control valve 164 (εee Fig. 10) , and pump drive signal LL for turning on centrifugal pump 178, in this example, for transferring fluid from drain port 64 back into tank T7. When a fluid interface or change from clear aqueouε in drain port 64 iε detected via controller 146 sensing a change in state of fluid phase signal 78, controller 146 terminates control signal GG and drive signal LL for closing valve 164, and turning off pump 178, respectively. Thereafter, control signal NN is generated for opening control valve 182, and control signal "00" is generated for opening control valve 184 (pressure relief valve) , for draining fluid from mixing tank T2 through the inlet portions of control valveε 108, 110, 112, and 164, through fluid drain lines 118, 166, 116, and 114, through manifold 126, and fluid drain line 168, through valve 182, into the second wash interface tank or pot 151. In this example, such drainage is provided for a period of one minute, after which time control signals NN and "00" are terminated for opening valves 182 and 184.

Also, during the copper solution proceεεing, in one embodiment of the invention, at the end of each second wash cycle, or on some other schedule depending upon acid usage, controller 146 is programmed to turn on the acid regeneration alarm 170, and to generate control signal P for turning on pump 74, to transfer acid laden with copper from tank T5 to the holding tank T6 for electrowinning. A scheduled basis for such tranεfer iε required, since in the copper extraction embodiment of the present system, very strong acid is used for copper stripping, too strong to monitor by pH. When controller 146 senses that level signal LS10 changes εtate from +5 voltε to 0 volt, for example, control signal P is terminated, for turning off pump 74. The copper iε extracted from the acid εolution by plating it out via an electrowinning proceεε and apparatuε either contained in tank T6 or coupled thereto, in this example. Ideally, acid is regenerated by electrowinning, so no additional acid would be needed under ideal conditions. In practice, small amounts of acid are lost, and based upon a manual analysiε, acid iε added as required. The regenerated acid is pumped back into acid tank T5 via controller 146 generating pump drive signal DD to turn on pump 152. Since electrowinning is a continuous process, not batch, pumps 74 and 152 are typically operating at the same time for circulating acid between tanks T5 and T6 in this example. The retrieved copper is removed from tank T6. Note that the copper can alternatively be extracted from the acid via off site procesεing.

With further reference to Fig. 9, note that controller 146, for proceεεing EDTA copper εolution, monitorε or εenεeε pH signalε pHl through pH4. Alεo, level εignalε LSI through LS14 are εenεed or monitored. Relative to the εyεtem configuration of Fig. 2, the configuration of Fig. 9 alεo requireε that controller 146 generate additional control εignalε DD through PP, aε shown. The syεtemε or apparatus of Figε. 2 and 9 have been deεcribed above for uεe in the batch εolvent extraction treatment of chelated nickel and copper solutions, respectively. However, these syεtems are also suitable for use with any batch solvent extraction process in which the organic solvent is lesε denεe than water. Exampleε include the extraction of copper from εpent ammoniacal etch εolution, removal of metals from contaminated ground water, extraction of amino acids from fermentation broth, extraction of aromatic sulfonic acidε from εulfuric acid, and so forth. The organic solvent may consiεt either of

1) a solution of an extractant in an organic diluent, where the solute must interact with the extractant in order to distribute into the organic solvent, or

2) an organic diluent only, where the solute distributeε from the aqueouε phaεe to the organic phaεe by virtue of εimple εolubility.

The exampleε cited above would relate to the former caεe (1) while the latter caεe (2) would be exemplified by the extraction of benzoic acid from an acidic aqueous feed solution into toluene, followed by regeneration by stripping with aqueous sodium hydroxide to produce sodium benzoate.

The apparatus is particularly suited for situationε where process automation and unattended operation are important, where croεε contamination between the extraction feed solution and the regeneration solution must be avoided, or both. Croεε-contamination iε particularly important for example, where impuritieε in the feed solution muεt not build up in the product or regeneration solution, because such impurities interfere with subsequent processing or are deleterious to the product's use. Cross- contamination avoidance is alεo important where the raffinate from extraction muεt be extremely low in reεidual εolute concentration (εuch aε for environmental purposes) , and very small contamination of concentrated regeneration solution into the discharge raffinate would cause it to exceed regulated limitε, aε previouεly mentioned. Depending upon the application for proceεεing required, the εyεtemε of Figε. 2 and 9 may not be required to incorporate wash tanks T4 and T7, for example. In such instances, these syεtems or apparatus can be simplified by elimination of the wash cycles.

Although variouε embodimentε of the invention are deεcribed herein for purpoεeε of illuεtration, they are not meant to be limiting. Thoεe of εkill in the art may recognize odificationε that can be made in the illuεtrated embodiments. Such modifications are meant to be covered by the spirit and scope of the appended claims.

Claims

What is claimed is: 1. A procesε compriεing steps of:

(I) providing

(A) a liquid aqueous solution comprising (1) a com- ponent of metal cations selected from the group consiεting of copper, nickel, and mixtureε there¬ of and (2) a component of chelating agentε, ex- cluεive of phenolic oximeε and εubεtituted 8-hy- droxyquinolineε, for at leaεt part of the metal cations in component (A) (1) and

(B) a liquid organic phase compriεing (1) an organic εolvent component εelected from the group of sol¬ vents that are liquid at 25° C, have a maximum solubility in water at 25° of 0.1 % by weight, and are composed of molecules that contain no atoms other than carbon, hydrogen, and halogen atoms, except that each molecule may contain not more than one moiety selected from the group con¬ siεting of: 0 0 0

-0-C II-, -CII-, -CI-, and -CI-O-CI- per molecule of εolvent, and mixtures thereof and (2) a complexing extractant component the relative amountε of liquids (A) and (B) being such that after mixing the two liquids and allowing the re¬ sulting mixture to settle, distinct aqueous and organ¬ ic liquid phaseε will be formed;

(II) mixing liquidε (I) (A) and (I) (B) together with εuffi- cient agitation for a εufficient time to cauεe the tranεfer of at leaεt 50 % of at leaεt one of the nick¬ el cationε, the copper cations, or both the nickel and the copper cations present in liquid (I) (A) before mixing to transfer to the organic phase of the mixture of liquids (I) (A) and (I) (B) ; and

(III) maintaining the mixture formed in step (II) suffi¬ ciently nearly quiescent to allow the mixture to εep- arate into distinct aqueous and organic phaseε; and (IV) removing the organic phase formed in step (III) from contact with the aqueous phase formed in step (III) .

2. A process according to claim 1, wherein the complexing extractant component is selected from the group consisting of alkyl substituted 8-hydroxyquinolines and of phenolic ketoximes and aldoximes conforming to the general chemical formula (I) :

OH NOH

where a is a positive integer with a value in the range from 1 to 4 inclusive; each of the number "a" of R groups present in the molecule is independently selected from the group consisting of saturated aliphatic moieties having one free valence and from 1 to 25 carbon atoms, ethylenically unsaturated aliphatic moieties having one free valence and from 3 to 25 carbon atoms, and moieties conforming to the general chemical formula -O-R* ^• , where R¹ * is selected from the group consisting of saturated aliphatic moieties having one free valence and from 1 to 25 carbon atoms and ethylen¬ ically unsaturated aliphatic moieties having one free val¬ ence and from 3 to 25 carbon atoms; and R¹ is selected from the group consisting of hydrogen, saturated aliphatic moi- eties having one free valence and from 1 to 25 carbon at¬ oms, ethylenically unsaturated aliphatic moieties having one free valence and from 3 to 25 carbon atoms, and moie¬ ties conforming to the general formula -CH₂C₆H₄-R' ' , where C₆H₄ represents a benzene ring with two free valences formed by removing two hydrogen atoms, which may be from any two positions on the ring; and R' * has the same meaning aε above; all with the proviso that the total number of carbon atoms in the group R* and the "a" R groups is in the range from 3 to 25.

3. A process according to claim 2, wherein the complexing extractant component is selected from the group conεiεting of compounds conforming to formula I when a = 1, R is a straight or branched chain alkyl group having from 7 to 12 carbon atoms and attached to the position para to the hy- droxyl group, and R' is hydrogen or methyl.

4. A procesε according to claim 3, wherein the ratio of the number of moleε of complexing extractant to the number of moleε of metal ionε εelected to be extracted that are present in the mixture formed in step (II) is at least 2:1 and the organic solvent component of (I) (B) has a solubil¬ ity in water of not more than 0.01 % by weight.

5. A procesε according to claim 4, wherein the metal cat- ionε are nickel and the chelating agent iε εelected from the group conεiεting of citric acid, malic acid, glycolic acid, tartaric acid, εuccinic acid, lactic acid, glycine and their εalts.

6. A process according to claim 5, wherein the pH value of component (I) (A) is in the range from 7 - 12.5, and the process compriseε the following additional εteps:

(V) mixing the organic phaεe εeparated in εtep (IV) with an aqueouε waεh liquid phaεe containing a total molarity of acetate ionε pluε acetic acid in the range from about 0.05 to about 1.0 molar and having a pH in the range from about 3.7 to about 5.6, the relative amountε of the organic phase separated in step (IV) and the aqueous wash liquid being such that after mixing the two liquids and allowing the resulting mixture to settle, distinct aqueous and organic liquid phases will be formed, said mixing being continued for a εufficient time that the level of impurities of the organic phase separated in step (IV) iε reduced by the tranεfer of εome impuritieε into the aqueouε waεh liquid phaεe; and (VI) maintaining the mixture formed in εtep (V) εufficiently nearly quiescent to allow the mixture to separate int distinct aqueous and organic phases; and (VII) removing the organic phase formed in step (VI) from contact with the aqueous phaεe formed in εtep (VI) .

7. A proceεε according to claim 4, wherein the metal cationε are copper and the chelating agent iε εelected from the group consisting of (ethylenedinitrilo) -tetraacetic acid, N,N,N' ,N'-tetrakiε-2-hydroxypropyl-ethylenediamine, and their salts.

8. A process according to claim 1, wherein the chelating agent component is selected from the group consiεting of (ethylenedinitrilo)-tetraacetic acid and itε salts, and the pH value of component (I) (A) is in the range from 11.5 - 13, and the proceεε comprises the following additional steps:

(V) mixing the organic phase separated in step (IV) with an aqueous wash liquid phase containing sulfate as the predominant anionε and having a total ionic molarity in the range from about 0.05 to about 5.0 molar and a pH in the range from about 3.5 to about 10, the relative amountε of the organic phase separated in step (IV) and the aqueouε wash liquid being such that after mixing the two liquids and allowing the resulting mixture to settle, distinct aqueous and organic liquid phases will be formed, said mixing being continued for a sufficient time that the impurity level of the organic phase separated in step (IV) is reduced by the transfer of εome impuritieε into the aqueouε waεh liquid phaεe; and

(VI) maintaining the mixture formed in step (V) sufficient- ly nearly quiescent to allow the mixture to separate into distinct aqueous and organic phases; and (VII) removing the organic phase formed in step (VI) from contact with the aqueous phase formed in step (VI) .

9. A process according to claim 7, wherein the chelating agent component iε N.N ,N' ,N'-tetrakiε-2-hydroxypropyl- ethylenediamine, the complexing extractant consists of ketoximes only, and the pH value of component (I) (A) is in the range from 6 - 9.5.

10. A process according to claim 7, wherein the chelating agent component is N_fN,N' ,N'-tetrakis-2-hydroxypropyl-eth- ylenediamine, the complexing extractant conεiεtε of aldox- imeε only, and the pH value of component (I) (A) iε in the range from 6 - 11.

11. A proceεε according to claim 10, wherein the complex¬ ing extractant component iε selected from the group con- sisting of 2-hydroxy-5-octylbenzaldoxime, 2-hydroxy-5-non- ylbenzaldoxime, 2-hydroxy-5-dodecylbenzaldoxime, 2-hydroxy- 5-heptylbenzaldoxime, and mixtures thereof, and the frac¬ tion of the metal cations transferred from the aqueous solution to the organic phase in step (II) iε at leaεt 90 %.

12. A process according to claim 9, wherein the complexing extractant component is selected from the group consisting of 2-hydroxy-5-nonylbenzophenone oxime, 2-hydroxy-5-dodec- ylbenzophenone oxime, 2-hydroxy-5-nonylacetophenone oxime, 2-hydroxy-5-dodecylacetophenone oxime, 2-hydroxy-5-octyl- acetophenone oxime, 2-hydroxy-5-heptylacetophenone oxime, and mixtures thereof, and the fraction of the metal cations tranεferred from the aqueouε εolution to the organic phaεe in step (II) is at least 90 %.

13. A procesε according to claim 8, wherein the complexing extractant component is εelected from the group conεisting of 2-hydroxy-5-nonyl oxime, 2-hydroxy-5-dodecylbenzophenone oxime, 2-hydroxy-5-nonylacetophenone oxime, 2-hydroxy-5-do- decylacetophenone oxime, 2-hydroxy-5-octylacetophenone ox- ime, 2-hydroxy-5-heptylacetophenone oxime, 2-hydroxy-5-oct- ylbenzaldoxi e, 2-hydroxy-5-nonylbenzaldoxime, 2-hydroxy-5- dodecylbenzaldoxime, 2-hydroxy-5-heptyl-benzaldoxime, and mixtures thereof, and the fraction of the metal cations transferred from the aqueouε solution to the organic phase in step (II) is at least 90 %.

14. A procesε according to claim 7 , wherein the complexing extractant component iε εelected from the group consisting of 2-hydroxy-5-nonylbenzophenone oxime, 2-hydroxy-5-dodec- ylbenzophenone oxime, 2-hydroxy-5-nonylacetophenone oxime, 2-hydroxy-5-dodecylacetophenone oxime, 2-hydroxy-5-octyl- acetophenone oxime, 2-hydroxy-5-heptylacetophenone oxime, 2-hydroxy-5-octylbenzaldoxime, 2-hydroxy-5-nonylbenzaldox- ime, 2-hydroxy-5-dodecylbenzaldoxime, 2-hydroxy-5-heptyl- benzaldoxime, and mixtures thereof, and the fraction of the metal cations transferred from the aqueous solution to the organic phase in εtep (II) iε at least 90 %.

15. A procesε according to claim 6, wherein the complexing extractant component iε εelected from the group consisting of 2-hydroxy-5-nonylbenzophenone oxime, 2-hydroxy-5-dodec- ylbenzophenone oxime, 2-hydroxy-5-nonylacetophenone oxime, 2-hydroxy-5-dodecylacetophenone oxime, 2-hydroxy-5-octyl- acetophenone oxime, 2-hydroxy-5-heptylacetophenone oxime, 2-hydroxy-5-octylbenzaldoxime, 2-hydroxy-5-nonyl-benzald- oxime, 2-hydroxy-5-dodecylbenzaldoxime, 2-hydroxy-5-heptyl- benzaldoxime, and mixtures thereof, and the fraction of the metal cations transferred from the aqueouε εolution to the organic phase in step (II) is at least 90 %.

16. A procesε compriεing steps of:

(i) depositing a plating consisting predominantly of a metal selected from the group consisting of nickel and copper on a solid surface by contacting the solid sur¬ face with a specified quantity of an electrolesε plat¬ ing εolution including an amount of chelating agent, excluεive of phenolic oximes and substituted 8-hydrox- yquinolineε, that iε εufficient to chelate at leaεt 1 % of the ionε therein of the metal or metalε being plated, εaid depoεiting being continued until the plating formed no longer meetε preselected criteria of quality and the electrolesε plating solution iε there¬ fore εpent; and (ii) extracting at least part of the nickel, the copper, or both the nickel and the copper contents of the speci¬ fied volume of the spent electroless plating solution from the end of εtep (i) into an organic liquid phaεe by a proceεs comprising steps of:

(I) providing a liquid organic phase comprising (1) an organic solvent component selected from the group of εolvents that are liquid at 25° C and have a maximum solubility in water at 25° of 0.1

% by weight and (2) a complexing extractant se¬ lected from organic alkyl substituted salicy1- aldehyde oximes, alkyl substituted 2-hydroxyalka- nophenone oximes, alkyl subεtituted 8-hydroxy- quinolineε, and mixtures thereof, the relative amounts of said liquid organic phase and of the specified quantity of spent electro¬ less plating solution from step (i) being such that after mixing these two components and allow- ing the resulting mixture to settle, distinct aqueous and organic liquid phases will be formed;

(II) mixing the liquid organic phase and the specified quantity of εpent electroleεε plating εolution from εtep (ii) (I) together with εufficient agita- tion for a εufficient time to cause the transfer of at least part of the nickel cations, the cop¬ per cations, or both the nickel and the copper cationε preεent in the specified quantity of spent electroleεε plating εolution before mixing to transfer to the organic phase of the mixture of liquids; and (III) maintaining the mixture formed in step (II) suf¬ ficiently nearly quieεcent to allow the mixture to εeparate into distinct aqueous and organic phases; and (IV) removing the organic phase formed in step (III) from contact with the aqueous phase formed in step (III).

17. A proceεε according to claim 16, wherein the complex¬ ing extractant iε εelected from the group conεiεting of al¬ kyl substituted 8-hydroxyquinolines and of phenolic ketox¬ imes and aldoximes conforming to the general chemical form¬ ula (I) :

OH N0H

(R)

where a is a positive integer with a value in the range from 1 to 4 inclusive; each of the number "a" of R groups present in the molecule is independently selected from the group consiεting of saturated aliphatic moieties having one free valence and from 1 to 25 carbon atoms, ethylenically unsaturated aliphatic moieties having one free valence and from 3 to 25 carbon atoms, and moietieε conforming to the general chemical formula -O-R¹ *, where R¹ ' is selected from the group consisting of saturated aliphatic moieties having one free valence and from 1 to 25 carbon atomε and ethylen¬ ically unsaturated aliphatic moieties having one free val- ence and from 3 to 25 carbon atoms; and R¹ is selected from the group consisting of hydrogen, saturated aliphatic moie¬ ties having one free valence and from 1 to 25 carbon atoms, ethylenically unsaturated aliphatic moieties having one free valence and from 3 to 25 carbon atoms, and moieties conforming to the general formula -CH₂C₆H₄-R' ' , where C₆H₄ representε a benzene ring minus two hydrogen atoms, which may be in any two positions on the ring and R¹ ' haε the εame meaning aε above; all with the proviso that the total number of carbon atoms in the group R^f and the "a" R groups is in the range from 3 to 25.

18. A procesε according to claim 17, wherein the complex¬ ing extractant is selected from the group consiεting of compoundε conforming to formula I when a = 1, R iε a εtraight or branched chain alkyl group having from 7 to 12 carbon atoms and attached to the position para to the hy¬ droxyl group, and R* is hydrogen or methyl.

19. A procesε according to claim 18, wherein the com¬ plexing extractant iε εelected from the group conεiεting of 2-hydroxy-5-nonylbenzophenone oxime, 2-hydroxy-5-dodecyl- benzophenone oxime, 2-hydroxy-5-nonylacetophenone oxime, 2- hydroxy-5-dodecylacetophenoneoxime, 2-hydroxy-5-octylacet- ophenone oxime, 2-hydroxy-5-heptylacetophenone oxime, 2- hydroxy-5-octylbenzaldoxime, 2-hydroxy-5-nonyl- benzaldoxime, 2-hydroxy-5-dodecylbenzaldoxime, 2-hydroxy-5- heptylbenzaldoxime, and mixtureε thereof.

20. A proceεε according to claim 19, wherein the number of moleε of complexing extractant to the number of moles of metal ionε εelected to be extracted that are preεent in the mixture formed in εtep (ii) (II) iε at leaεt 2:1 and the liquid organic εolvent haε a solubility in water of not more than 0.01 % by weight.

21. An automated batch procesεing εyεtem for extracting at leaεt one εolute from an aqueouε feed solution, comprising: a first tank for permanently containing an organic solvent; feed means operable for delivering pH adjusted aqueous feed solution to said first tank; mixing meanε in said first tank operable for mixing together the contents of said first tank including said organic solvent and said aqueous feed solution, for causing said organic solvent to extract said solute from said aqueous feed solution, whereby after a predetermined period of time after mixing is terminated the mixture separates into an aqueous phase depleted of solute, and an organic phase with solute; first drain meanε operable for removing εaid aqueouε phaεe from said firεt tank; regenerant meanε operable for delivering regenerant solution into said first tank for regenerating εaid organic εolvent by removing εaid εolute from said organic phase, whereby said mixing means is further operable for mixing said regenerant solution with said organic phase for a predetermined period of time, whereby after mixing the mixture separates into an organic phase consisting of said organic solvent depleted of solute, and a regenerant phaεe conεiεting of said regenerant solution laden with solute; and second drain means operable for removing said regenerant solution from said first tank thereby leaving regenerated organic solvent in said first tank for use in a subsequent extraction cycle.

22. The syεtem of claim 21, further including: firεt wash means operable for delivering a first wash solution to said first tank immediately after the draining of said aqueous phase from εaid firεt tank, said mixing means being operable for mixing said first wash solution with said organic phase, for removing impuritieε from the latter, whereby after mixing iε terminated the mixture εeparateε into an organic phase and aqueous phaεe; and third drain means operable for removing said aqueous phase from said firεt tank, leaving a washed organic phaεe laden with εolute in εaid first tank for regeneration via said regenerant means.

23. The syεtem of claim 22, further including: second wash means operable for delivering a second wash εolution to said first tank after said regenerant solution is removed from εaid firεt tank; εaid mixing meanε being operable uεed for mixing said second wash solution with said organic solvent, for washing said organic εolvent, whereby after mixing the mixture εeparates into an aqueous phase, and washed organic solvent; and fourth drain meanε operable for removing εaid aqueous phaεe from εaid firεt tank.

24. The εyεtem of claim 21, further including: controller means programmed for automatically controlling the operation of said feed means, mixing means, first drain means, regenerant means, and second drain means.

25. The εystem of claim 21, further including: a drain port at the bottom of said first tank; firεt and εecond interface pots; firεt and εecond valve meanε connected between εaid drain port and firεt and εecond interface pots, respectively, said first valve means being operable for drawing potential crosε contaminantε away from εaid drain port into said first interface pot subsequent to operation of said first drain means, and εaid εecond valve meanε being operable for drawing potential croεε contaminantε away from εaid drain port into said second interface pot subεequent to operation of said second drain means, thereby leaving a common liquid composition between that in said firεt tank and firεt valve meanε prior to regenerating said organic solvent, and a common liquid compoεition between that in εaid firεt tank and εaid εecond valve meanε prior to initiating a subsequent extraction cycle.

26. The syεtem of claim 21, further including: a firεt drain port at the bottom of said first tank; first and second interface pots; said first drain means including a first control valve having an inlet port connected to said first drain port, said inlet port being configured with a cleanout drain port, whereby with said firεt control valve cloεed, fluid can be drawn through εaid inlet port into an inlet portion of said firεt control valve, and therefrom out of the cleanout drain port; εaid εecond drain meanε including a εecond control valve having an inlet port connected to εaid drain port, said inlet port being configured with a cleanout drain port, whereby with εaid εecond control valve closed, fluid can be drawn through said inlet port into an inlet portion of said second control valve, and therefrom out of the cleanout drain port; a manifold including first and second inlet ports connected to said cleanout drain ports of said first and second control valves, respectively, and said manifold further including firεt and εecond outlet portε; third and fourth control valveε connected between said first and second outlet ports of εaid manifold and εaid firεt and second interface potε, reεpectively; said first control valve being operable to an open condition with said second, third, and fourth control valves closed, for removing raffinate from said first tank; said third control valve being operable to an open condition with εaid firεt, εecond, and fourth control valveε closed, for drawing fluid from said first drain port, through the inlet portions of said first and second control valves, through εaid manifold, and into εaid firεt interface pot, for insuring a common liquid composition between liquid in said first tank, and inlet portions of said first, second, and third control valves, prior to initiating a subεequent cycle of operation, thereby εubstantially avoiding cross contamination problems; said second control valve being operable to an open condition with said first, third and fourth control valves closed, for removing regenerant solution from said first tank; and said fourth control valve being operable to an open condition with said first, second, and third control valves cloεed, for draining fluid from εaid first drain port, through the inlet portions of said first and second control valves, through εaid manifold, and into said second interface pot, for insuring a common liquid composition between liquid in said first tank, and inlet portions of said first, εecond, and fourth control valveε prior to initiating a subsequent cycle of operation, thereby subεtantially avoiding cross-contamination problems.

27. The syεtem of claim 21, further including: a drain port at the bottom of said first tank; and a screen located near the bottom of said first tank, over said drain port, for enhancing the coalescence of residual mixed phaseε.

28. The εyεtem of claim 24, wherein εaid feed meanε includeε: a εecond tank for containing aqueous feed solution; mixing means in said second tank operable for mixing together the contents therein; level senεing means in said second tank for producing a firεt level signal indicative of the level of fluid therein; first pump means operable for delivering aqueous feed solution from a source thereof to said second tank; εecond pump meanε operable for pumping pH adjuεting εolution from a εource thereof to εaid εecond tank; third pump meanε operable for pumping pH adjuεted aqueouε feed εolution from εaid εecond tank to said first tank; first pH εenεing meanε in said second tank for producing a firεt pH εignal indicative of the pH of εaid aqueouε feed solution; and εaid controller meanε being further programmed for operating εaid firεt pump meanε until said firεt level εignals indicate said aqueous feed solution has attained a predetermined level, followed by sensing said first pH εignal, whereby if the pH is not at a predetermined value, said second tank mixing meanε is turned on and said εecond pump meanε operated until the pH of the aqueouε feed εolution attainε the predetermined value.

29. The system of claim 28, further including: level senεing meanε in εaid first tank for producing a second level signal indicative of the level of fluid in said first tank; and said controller means being further programmed for initiating an extraction cycle by senεing said second level signal and operating said third pump means, until said second level signal is indicative of the fluid level in said first tank reaching a predetermined level, followed by turning on said first tank mixing meanε for a predetermined time, whereafter a predetermined quieεcent period iε initiated to permit any emulεion formed in εaid first tank to break apart.

30. The system of claim 24, further including: a drain port at the bottom of said first tank; and fluid layer sensor meanε connected to εaid drain port for producing a liquid phaεe εignal indicative of the liquid within or paεεing through said drain port at a given time changing from a clear aqueous.

31. The syεtem of claim 30, wherein said firεt drain means includeε: a second tank for containing raffinate; first fluid transfer means connected between said drain port and said second tank, operable for transferring fluid from said drain port to εaid second tank; and said controller means being further programmed to operate said first fluid transfer means while senεing εaid liquid phaεe εignal, for tranεferring fluid from εaid firεt tank to εaid εecond tank until a clear aqueouε phaεe iε no longer εenεed, after which time operation of εaid fluid tranεfer meanε is terminated.

32. The εyεtem of claim 31, wherein εaid first fluid transfer means includeε: a pump; and a first control valve operable to an open condition connected in serieε with εaid pump; εaid controller means being further programmed for opening said first control valve followed by operating εaid pump, for pumping fluid from εaid drain port to εaid εecond tank.

33. The εyεtem of claim 32, wherein said first drain means further includes: said first control valve including an inlet port configured with a cleanout drain port, whereby with the valve turned off, fluid can be drawn through the inlet port into an inlet portion of the valve, and therefrom out of the cleanout drain port; a raffinate interface pot; a second control valve connected between said raffinate interface pot, and said cleanout drain port of εaid firεt control valve, operable for opening to provide a fluid path there between; said controller means being further programmed for subsequent to terminating operation of said first control valve, operating said εecond control valve to open for cauεing a predetermined amount of fluid to flow from εaid drain port of said first tank, through said inlet and cleanout drain ports of εaid first control valve, and through said second control valve into said raffinate interface pot, for establiεhing a common fluid composition from said first tank to said second control valve, thereby preventing cross contamination of said organic phase from residual fluidε aεsociated with the drain port of said firεt tank, when a εubεequent cycle of operation is initiated.

34. The syεtem of claim 24, wherein εaid regenerant means includeε: a εecond tank for containing regenerant εolution; mixing meanε in εaid εecond tank operable for mixing together the contentε therein; level sensing means in said second tank for producing first level εignalε indicative of the level of fluid therein; firεt pump meanε operable for delivering freεh concentrated regenerant εolution from a source thereof to said second tank; second pump means operable for pumping regenerant solution from said εecond tank to εaid firεt tank; firεt pH sensing means in said second tank for producing a first pH signal indicative of the pH of εaid regenerant solution; third pump means operable for pumping water from a source thereof into εaid εecond tank; and εaid controller meanε being further programmed for prior to a regeneration cycle, operating as necessary said first and third pump means, and said mixing means, while sensing said first pH signal for restoring and obtaining a predetermined level of regenerant εolution in εaid εecond tank at a predetermined pH level.

35. The syεtem of claim 34, further including: level εenεing meanε in εaid first tank for producing a second level signal indicative of the level of fluid in said first tank; and εaid controller meanε being further programmed for initiating a regeneration or organic εolvent recovery cycle by εucceεεively operating εaid εecond pump meanε until εaid εecond level εignal iε indicative of the fluid in εaid firεt tank attaining a predetermined level, terminating operation of said second pump, operating said mixing means in said first tank for a predetermined period of time, and thereafter providing a predetermined quiescent time period for permitting any emulsion to break apart.

36. The syεtem of claim 30, further including: εaid regenerant meanε including: a second tank for containing said regenerant solution; a first pump operable for tranεferring regenerant εolution from εaid εecond tank to εaid first tank; said second drain means including: a second pump; and a firεt control valve operable to an open condition, connected in εeries with said second pump between said first and εecond tankε; said controller being further programmed for operating said firεt pump at the initiation of a regeneration cycle until the level of fluid in εaid first tank attains a predetermined level, and for operating said second pump and first control valve near the end of a regeneration cycle for transferring used regenerant solution from said first tank to said second tank.

37. The syεtem of claim 36, further including: pH sensing meanε in εaid εecond tank for producing a pH εignal indicative of the pH of said regenerant solution; a third tank; a third pump connected between said second and third tank, operable for pumping regenerant solution from said second tank to εaid third tank; and said controller means being further programmed for senεing said pH εignal after tranεfer of used regenerant solution from said first tank to said second tank, responεive to the pH of εaid uεed regenerant εolution being above a predetermined pH value indicative of said regenerant solution being enriched with said solute, for operating said third pump for transferring enriched regenerant εolution from said second tank to said third tank.

38. The system of claim 37, further including: electrowinning means operable for removing said solute from said enriched regenerant εolution; and a fourth pump connected between said second and third tankε, operable for pumping reεtored regenerant εolution from said third tank to said εecond tank.

39. The syεtem of claim 36, wherein second drain means further includes: said first control valve including an inlet port configured with a cleanout drain port, whereby with the valve turned off, fluid can be drawn through the inlet port into an inlet portion of the valve, and therefrom out of the cleanout drain port; a regenerant εolution interface pot; a second control valve connected between said regenerant solution interface pot, and said cleanout drain port of said first control valve, operable for opening to provide a fluid path therebetween; said controller means being further programmed for subsequent to terminating operation of said first control valve, operating said second control valve to open for at leaεt a εufficient period of time for causing a predetermined amount of fluid to flow from said drain port of said first tank, through said inlet and cleanout drain ports of said first control valve, and through said second control valve into said regenerate solution interface pot, for establishing a common fluid composition from said firεt tank to said second control valve, thereby preventing cross contamination of said organic phase from residual fluids aεεociated with the drain port of εaid firεt tank, when a εubεequent cycle of operation iε initiated.

40. The system of claim 22, further including: a drain port at the bottom of said firεt tank; fluid layer sensor means connected to said drain port for producing a liquid phase signal indicative of the liquid within or pasεing through εaid drain port at a given time changing from a clear aqueous; said first waεh means including: a second tank for containing εaid first wash solution; and a first pump operable for transferring first wash solution from said εecond tank to εaid first tank; said third drain meanε including: a firεt control valve including an inlet port configured with a cleanout drain port, whereby with the valve turned off, fluid can be drawn through the inlet port into an inlet portion of the valve, and therefrom out of the cleanout drain port; a second pump connected in serieε with εaid firεt control valve between εaid drain port and εecond tank; a firεt wash interface pot; a second control valve connected between said first wash interface pot, and εaid cleanout drain port of εaid firεt control valve, said second control valve being operable for opening to establiεh a fluid path therebetween; and a controller programmed for εubεequent to terminating operation of εaid firεt control valve, operating εaid εecond control valve for at leaεt a sufficient period of time for causing a predetermined amount of fluid to flow from said drain port of said first tank, through εaid inlet and cleanout drain ports of said first control valve, and through εaid second control valve into said first wash interface pot, for establishing a common fluid composition from said first tank to said second control valve, thereby preventing cross contamination of said organic phase from residual fluidε aεsociated with the drain port of said first tank, when a subsequent cycle of operation is initiated.

41. The εystem of claim 23, further including: said second wash means including: a third tank for containing a εecond wash solution; a third pump operable for transferring second wash solution from said third tank to said first tank;

said fourth drain means including: a third control valve including an inlet port configured with a cleanout drain port, whereby with the valve turned off, fluid can be drawn through the inlet port into an inlet portion of the valve, and therefrom out of the cleanout drain port; a fourth pump connected in εeries with said third control valve between said drain port and third tank; a second wash interface pot; a fourth control valve connected between said second wash interface pot, and said cleanout drain port of said third control valve, said fourth control valve being operable to open for establishing a fluid path therebetween; and said controller being further programmed for subsequent to terminating operation of said third control valve, operating said fourth control valve to open for at least a εufficient period of time for causing a predetermined amount of fluid to flow from εaid drain port of εaid first tank, through εaid inlet and cleanout drain ports of εaid third control valve, and through εaid fourth control valve into εaid εecond waεh interface pot, for establishing a common fluid composition from said first tank to said fourth control valve, thereby preventing crosε contamination of εaid organic phaεe when a subεequent cycle of operation iε initiated.

42. The εystem of claim 33, further including: second fluid tranεfer means connected between said raffinate interface pot and said first tank, operable for transferring fluid from said raffinate interface pot to said firεt tank; εaid controller means being further programmed for operating said second fluid transfer means during an initial phase of each extraction cycle for transferring subεtantially all the fluids in the said raffinate interface pot to said first tank.

43. The syεtem of claim 36, further including: meanε operable for tranεferring fluid from said regenerant solution interface pot to said first tank; and said controller being further programmed for operating said fluid tranεferring meanε during an initial phase of each regeneration cycle, for transferring subεtantially all the fluid in εaid regenerant εolution interface pot to εaid firεt tank.

44. The εyεtem of claim 40, further including: meanε operable for tranεferring fluid from εaid firεt waεh interface pot to εaid first tank; and said controller being further programmed for operating said fluid transferring means during an initial phase of each first wash cycle, for transferring subεtantially all of the fluid in εaid first wash interface pot to said first tank.

45. The syεtem of claim 41, further including: meanε operable for tranεferring fluid from said second wash interface pot to said first tank; and said controller being further programmed for operating said fluid transferring means during an initial phase of each second wash cycle, for transferring substantially all the fluid in said second wash interface pot to said first tank.

46. A method for extracting a solute from an aqueous feed solution, comprising the steps of: measuring the pH of said aqueous feed solution; adjusting the level of pH of said aqueous feed εolution to a predetermined level; retaining an organic εolvent in a mixing tank at all ti eε; adding said pH adjusted aqueous feed solution to said mixing tank; mixing said pH adjusted aqueouε feed εolution with said organic solvent; permitting the resulting mixture to be quiescent for at least a period of time necessary for permitting organic and aqueous phaseε of the mixture to coalesce and separate into an organic phase with solute, and aqueous phase depleted of solute; draining aqueous phaεe from the coaleεced mixture; adding regenerant εolution to the remaining organic phaεe; mixing said regenerant acid solution and organic phase together for at leaεt a period of time necessary for transferring solute from the organic phase to said regenerant solution; permitting the mixture of regenerant solution and organic phase to be quiescent for at least a period of time permitting separation of organic and regenerant phases; pumping the regenerant phase portion from said mixing tank into a recovery tank; and retaining the regenerated organic solvent in said mixing tank for use in another extraction cycle.

47. The method of claim 46, further including the steps of: measuring the pH of regenerant solution in said recovery tank; draining solute enriched regenerant solution from said recovery tank for further recovery of said solute, when the pH thereof increases to above a predetermined level; and reusing said regenerant solution in a next cycle of regeneration when the pH thereof is below said predetermined level.

48. The method of claim 47, wherein said step of measuring the pH of regenerant solution in said recovery tank, further includes the step of: energizing an alarm when the pH of said regenerant solution increaseε to above εaid predetermined level, for initiating εaid step of draining solute enriched regenerant solution from said recovery tank.

49. The method of claim 46, further including before said step of adding regenerant solution to the remaining organic phase, the step of: washing said organic phase with a first wash solution to remove impurities.

50. The method of claim 46, wherein said adjusting step further includes adding a pH adjusting solution to said aqueous feed solution as required to obtain the predetermined pH level.

51. The method of claim 46, further including after said step of adding regenerant solution to the remaining organic phaεe, the εtep of waεhing εaid organic phaεe with waεh εolution to remove impuritieε from εaid organic phaεe.

52. The method of claim 46, further including the steps of subεtantially draining any potential croεε contamination fluids from a drain port of said mixing tank after each one of said draining, and pumping εteps.

53. The method of claim 49, further including in said first wash solution a buffering agent for controlling the pH of said first wash solution.

54. An automated batch processing syεtem for extracting a εolute from an aqueouε feed εolution, compriεing: a firεt tank for containing εaid aqueouε feed εolution for processing; first pH senεing means immersed in said aqueouε feed solution in εaid firεt tank, for producing a firεt pH εignal indicative of the pH of εaid aqueous feed solution; first fluid transfer means for transferring pH adjusting solution from a source thereof into said first tank, for adjusting the pH of said aqueous feed solution therein to a predetermined value; first mixer means in said first tank, responsive to a first mix signal for mixing together said aqueous feed εolution and εaid pH adjusting solution; a second tank permanently containing an organic solvent lesε dense than water; second fluid tranεfer meanε operable for tranεferring pH adjusted aqueous feed solution from said firεt tank to εaid second tank; second mixer means in said εecond tank, reεponεive to a second mix signal for mixing together εaid organic εolvent and aqueouε feed εolution, for cauεing εaid εolute to paεε from the aεεociated εaid aqueous feed solution to said organic solvent, whereafter termination of said second mix signal, the mixture εeparates into an aqueous phase depleted of solute, and an organic phase with solute; a drain port located at the bottom of said second tank; fluid layer senεor meanε connected to εaid drain port for producing a liquid phaεe εignal indicative of the liquid within or paεεing through εaid drain port at a given time changing from clear aqueouε; a third tank for containing regenerant solution for regenerating organic εolvent in εaid εecond tank; third fluid transfer means connected between said first drain port and a waste storage point, operable for transferring the aqueouε phase and raffinate from said second tank to said waste storage point; fourth fluid transfer means operable for transferring regenerant solution from said third tank to said second tank; fifth fluid transfer means connected between said drain port and said third tank, operable for transferring used regenerant from said second tank to said third tank; a first interface pot for temporary storage of fluid drained from said drain port, to avoid cross contamination in later procesεing, after paεεage of raffinate therethrough; εixth fluid transfer means connected between said third transfer meanε and first interface pot, operable for tranεferring fluid from εaid drain port, through an inlet portion of εaid third fluid tranεfer means, to said first interface pot; seventh fluid transfer means connected between said first interface pot and said second tank, operable for transferring fluid from εaid firεt interface pot to εaid εecond tank; a εecond interface pot for temporary εtorage of fluid drained from εaid drain port, to avoid cross contamination in later procesεing, after paεεage of uεed regenerant εolution therethrough; eighth fluid tranεfer meanε connected between εaid fifth fluid tranεfer meanε and εecond interface pot, operable for tranεferring fluid from εaid drain port, through an inlet portion of εaid fifth fluid tranεfer meanε, to εaid εecond interface pot; ninth fluid tranεfer means connected between said second interface pot and said second tank, operable for transferring fluid from said second interface pot back to said second tank; and controller means programmed for automatically operating εaid εyεtem through a plurality of succesεive modeε of operation for accompliεhing the deεired extraction of εolute from the aqueouε feed εolution via said organic εolvent in εaid εecond tank, followed by regeneration of said organic solvent via said regenerant εolution within εaid εecond tank, the programming including εensing of said first pH signal, and operation of said firεt through ninth fluid tranεfer meanε in a predetermined sequence for predetermined periods of time whereby said organic solvent remains in said εecond tank at all timeε.

55. The εystem of claim 54, wherein the programming of said controller means for providing said modes of operation, includeε: firεt mode operation means for adjusting the pH of said aqueous feed solution, if necessary, responsive to said first pH signal being different than a predetermined value, for operating said first fluid transfer means, and for producing said first mix signal, for a period of time necessary to change said first pH εignal to said predetermined value; second mode of operation means for initiating an extraction cycle, reεponεive to εaid firεt pH signal being at said predetermined value, both for operating said second fluid transfer means for a period of time neceεεary for tranεferring a given quantity of pH adjusted aqueous feed solution to said second tank, and for operating εaid seventh fluid transfer means for a predetermined period of time; third mode of operation means for causing said organic solvent to extract said solute from said aqueous feed solution, providing for succesεively producing said second mix signal a predetermined period of time after the termination of operation of said second and seventh fluid transfer means, terminating said second mix signal after a predetermined period of time, providing a quiescent period of time for permitting an emulεion of εaid organic εolvent and aqueouε feed solution to coalesce, operating said sixth fluid transfer means for a predetermined period of time to remove any organic or unmixed aqueous solution from drain lines connected to said first interface pot, operating said third fluid transfer means upon sensing said liquid phase signal is indicative of a clear liquid phase, thereafter terminating operation of said third fluid transfer means upon sensing said liquid phase signal is no longer indicative of clear aqueous phase, operating said sixth fluid transfer means for a predetermined period of time, increasing by one the count on a preestablished extraction counter having a predetermined count limit, and repeating εaid third mode of operation in an iterative manner until εaid extraction counter reacheε the count limit, whereafter a next mode of operation means is entered into; and fourth mode of operation means for recovering solute from said organic solvent, including succesεively operating εaid fourth fluid transfer means, said ninth fluid transfer means, for a predetermined period of time, terminating operation of said fourth fluid transfer means after a period of time for filling said second tank to a predetermined level, producing εaid εecond mix signal for a predetermined period of time, providing another predetermined quiescent time period subsequent to terminating said εecond mix signal, thereafter operating εaid fifth fluid transfer means, terminating operation of said fifth fluid transfer means in response to said liquid phaεe εignal being no longer indicative of clear aqueouε phaεe, and operating εaid eighth fluid tranεfer meanε for at leaεt a εufficient period of time for draining regenerant εolution remaining in εaid drain port therefrom to εaid εecond interface pot.

56. The system of claim 55, further including: a fourth tank for containing a first wash solution for uεe in waεhing εaid organic εolvent after εaid third mode of operation means is completed, for removing impurities from said organic solvent prior to regeneration thereof; tenth fluid tranεfer meanε operable for tranεferring firεt waεh εolution from εaid fourth tank to εaid εecond tank; eleventh fluid transfer means connected between εaid firεt drain port and εaid fourth tank, operable for tranεferring uεed firεt wash solution from εaid drain port to εaid fourth tank; a third interface pot for temporary εtorage of reεidual uεed firεt waεh εolution from εaid drain port to avoid croεε contamination in later proceεεing; twelfth fluid tranεfer meanε operable for tranεferring fluid from said drain port, through an inlet portion of said eleventh fluid transfer meanε to εaid third interface pot; thirteenth fluid tranεfer meanε operable for tranεferring fluid from said third interface pot to said εecond tank; and said controller means being further programmed for providing a first wash mode operation means immediately after said third mode of operation means is completed, εaid first wash mode of operation meanε for removing impuritieε from said organic solvent, including succeεεively operating εaid tenth fluid tranεfer meanε for a predetermined period of time, operating εaid thirteenth fluid tranεfer meanε for a predetermined period of time, after terminating operation of εaid tenth and thirteenth fluid transfer means, thereafter producing said second mix signal for a predetermined period of time, after terminating said second mix εignal providing another predetermined settling time for permitting emulsionε to break up, thereafter operating εaid eleventh fluid tranεfer means, terminating operation of said eleventh fluid transfer means in response to said liquid phase signal being no longer indicative of a clear aqueous phase, operating said twelfth fluid transfer means for at least a sufficient period of time for draining a predetermined amount of residual first wash water and contaminants from said drain port to said third interface pot, and thereafter proceeding to said fourth mode of operation meanε.

57. The syεtem of claim 56, further including: a fifth tank for containing a second wash εolution for use in washing said organic solvent after said fourth mode of operation means is completed, for removing impurities from said organic εolvent prior to itε use in another cycle of extracting solute from said aqueous feed solution; fourteenth fluid transfer means operable for transferring second wash solution from said fifth tank to said second tank; fifteenth fluid transfer means connected between said drain port and said fifth tank, operable for transferring used second waεh εolution from said drain port to said fifth tank; a fourth interface pot for temporary storage of residual used εecond waεh εolution drained from εaid drain port, to avoid croεs contamination in later processing; sixteenth fluid transfer means operable for transferring fluid from εaid drain port, through an inlet portion of εaid fifteenth fluid tranεfer means, to εaid fourth interface pot; seventeenth fluid transfer means operable for transferring fluid from said fourth interface pot to εaid εecond tank; and εaid controller meanε being further programmed for providing a εecond waεh mode operation meanε immediately after εaid fourth mode of operation meanε iε completed, εaid εecond wash mode operation means for removing impurities from εaid organic εolvent, including succesεively operating εaid fourteenth fluid tranεfer meanε for a predetermined period of time, producing said seventeenth transfer signal for a predetermined period of time, thereafter producing εaid εecond mix εignal for a predetermined period of time, after terminating εaid εecond mix εignal providing another predetermined εettling time for permitting emulεionε to break up, thereafter operating εaid fifteenth fluid transfer means, terminating operation of said fifteenth fluid transfer means in response to said liquid phase signal being no longer indicative of a clear aqueous phase, operating εaid εixteenth fluid transfer means for a sufficient period of time for draining a predetermined amount of residual second wash water and contaminants from εaid drain port to εaid fourth interface pot, terminating εaid εixteenth transfer signal, and thereafter procesεing another batch of εaid aqueouε feed εolution for removal of εolute.

58. The εyεtem of claim 55, further including: a manifold having both individual inlet portε connected to εaid inlet portionε of εaid third and fifth fluid tranεfer meanε, reεpectively, and individual outlet portε connected to inlet portε of εaid εixth fluid transfer means and eighth fluid transfer means, respectively, for insuring a common fluid composition in fluid pathε therebetween before initiation of an extraction and regeneration cycleε of operation.

59. The εyεtem of claim 56, further including: a manifold having both individual inlet portε connected to εaid inlet portionε of εaid third, fifth, and eleventh fluid tranεfer meanε, reεpectively, and individual outlet ports connected to inlet ports of said sixth, eighth, and twelfth fluid transfer means, respectively, for insuring a common fluid composition in fluid paths therebetween before initiation of extraction, first wash, and regeneration cycles of operation.

60. The system of claim 58, wherein said manifold further includes: individual inlet ports connected to said inlet portionε of εaid eleventh and fifteenth fluid transfer means, respectively, and individual outlet ports connected to inlet ports of said third and fourth interface pots, respectively, for insuring a common fluid composition in fluid paths connected in common via said manifold before initiation of an extraction, firεt wash, regeneration, and second waεh cycles of operation.