CA1142452A - Purification of liquids with treated filter aid material and active particulate material - Google Patents
Purification of liquids with treated filter aid material and active particulate materialInfo
- Publication number
- CA1142452A CA1142452A CA000354601A CA354601A CA1142452A CA 1142452 A CA1142452 A CA 1142452A CA 000354601 A CA000354601 A CA 000354601A CA 354601 A CA354601 A CA 354601A CA 1142452 A CA1142452 A CA 1142452A
- Authority
- CA
- Canada
- Prior art keywords
- filter aid
- fibers
- filter
- aid material
- bed
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D37/00—Processes of filtration
- B01D37/02—Precoating the filter medium; Addition of filter aids to the liquid being filtered
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D37/00—Processes of filtration
- B01D37/03—Processes of filtration using flocculating agents
Abstract
PURIFICATION OF LIQUIDS WITH TREATED FILTER AID
MATERIAL AND ACTIVE PARTICULATE MATERIAL
A B S T R A C T
Disclosed is a method for removing impurities from a liquid, which method comprises passing the liquid through a filter bed comprising a mixture of fibrous filter aid material and an active particulate material. The filter aid material comprises 5 to 95%, by weight, of the bed, and has been treated with an electrolyte-type compound that produces a surface charge opposite to the normal surface charge by bonding to the surface of the filter aid material.
The invention also pertains to the improved filter bed.
MATERIAL AND ACTIVE PARTICULATE MATERIAL
A B S T R A C T
Disclosed is a method for removing impurities from a liquid, which method comprises passing the liquid through a filter bed comprising a mixture of fibrous filter aid material and an active particulate material. The filter aid material comprises 5 to 95%, by weight, of the bed, and has been treated with an electrolyte-type compound that produces a surface charge opposite to the normal surface charge by bonding to the surface of the filter aid material.
The invention also pertains to the improved filter bed.
Description
5~
PURIFICATION OF LIQUIDS WII'H TREATED E'ILTER AID
SPECIFICATION
The present invention relates to an improved method for removing impurities from a liquid, and to an improved filter bed.
U.S. Patent No. 4,177,142 describes and claims a method for removing impurities from a liquid, together with an improved filter bed, which employs a mixture of oppositely charged filter aid materials. These filter aid particles normall~ have a charge in aqueous suspension, and a portion of the particles is treated with a chemical compound to produce a surface charge which is opposite to the normal surface charge. A mixture of oppositely charged particles (normal charge and reverse charge) is produced, which results in a phenomenon known as "clumping" when the particles are mixed in aqueous suspension. The advantages of this clumping phenomenon are described in U.S. Patent No. 3,250,702, which is assigned to the assignee of this application.
Generally, the present invention relates to an im-provement upon the broader invention described and claimed inU.S. Patent No. 4,177,142. It is generally known in the art that certain mater:ials may be employed to remove either a narrow or a broad range of components from liquid streams through the phenomena of adsorption, absorption, or chemical reaction. For example, it is well known that activated carbon particles may be used to extract a broad range of components : ~.
:
5~Z
, from liquids.. Molecular sieves, such as zeolites, may also be useG tO extract components from liquids and ~ay, in some nstances, be designed to remove components o~ a very specific ~o~ecular size Iron sulfide particles, on the other hand, ra~re been employed to remove dissolved copper from liquid st-eams by reacting with the copper at the surface to form insoluble cupric sulfide. Various particulate materials may be used to extract undesired materials from water, such mater-als including carci~ogens, pesticides, and other toxic wastes.
1~ ,aese particulate materials, which may operate through theF'~enomena of`adsorption, absorption, or chemical reaction, are -e~erred to collectively herein as an "active particulate raterial " The foregoing are merely examples of such materials, and rurther examples are given herein.
1~ It is well known that many active particulate mater-ials, such as activated carbon, ténd to form densely packed beds, particularly in their finely divided st~te where they 2re most efficient. It is therefore difficult to utilize such ~aterials in performing the continuous filtration of liquid streams. However, in accordance with the present invention, it has been found that an active particulate co~ponent may be .i~ed with a treated fibrous filter aid material in order to "^lu~p," producing a mixture which exhibits a reduced pressure c~op as described in U.S. Patent l~o. 3,250,702. Thus, whereas
PURIFICATION OF LIQUIDS WII'H TREATED E'ILTER AID
SPECIFICATION
The present invention relates to an improved method for removing impurities from a liquid, and to an improved filter bed.
U.S. Patent No. 4,177,142 describes and claims a method for removing impurities from a liquid, together with an improved filter bed, which employs a mixture of oppositely charged filter aid materials. These filter aid particles normall~ have a charge in aqueous suspension, and a portion of the particles is treated with a chemical compound to produce a surface charge which is opposite to the normal surface charge. A mixture of oppositely charged particles (normal charge and reverse charge) is produced, which results in a phenomenon known as "clumping" when the particles are mixed in aqueous suspension. The advantages of this clumping phenomenon are described in U.S. Patent No. 3,250,702, which is assigned to the assignee of this application.
Generally, the present invention relates to an im-provement upon the broader invention described and claimed inU.S. Patent No. 4,177,142. It is generally known in the art that certain mater:ials may be employed to remove either a narrow or a broad range of components from liquid streams through the phenomena of adsorption, absorption, or chemical reaction. For example, it is well known that activated carbon particles may be used to extract a broad range of components : ~.
:
5~Z
, from liquids.. Molecular sieves, such as zeolites, may also be useG tO extract components from liquids and ~ay, in some nstances, be designed to remove components o~ a very specific ~o~ecular size Iron sulfide particles, on the other hand, ra~re been employed to remove dissolved copper from liquid st-eams by reacting with the copper at the surface to form insoluble cupric sulfide. Various particulate materials may be used to extract undesired materials from water, such mater-als including carci~ogens, pesticides, and other toxic wastes.
1~ ,aese particulate materials, which may operate through theF'~enomena of`adsorption, absorption, or chemical reaction, are -e~erred to collectively herein as an "active particulate raterial " The foregoing are merely examples of such materials, and rurther examples are given herein.
1~ It is well known that many active particulate mater-ials, such as activated carbon, ténd to form densely packed beds, particularly in their finely divided st~te where they 2re most efficient. It is therefore difficult to utilize such ~aterials in performing the continuous filtration of liquid streams. However, in accordance with the present invention, it has been found that an active particulate co~ponent may be .i~ed with a treated fibrous filter aid material in order to "^lu~p," producing a mixture which exhibits a reduced pressure c~op as described in U.S. Patent l~o. 3,250,702. Thus, whereas
2, activated-carbon, for example, has been principally used in-a batch-type treatment of liquids wherein it is suspended and t:~en filtered, the present invention enables the use of such ~terials in the treatment of a continuous stream. In addition, filter beds prepared in accordance with the present invention 3C r~y be utilized as an overlay over other types of ~ilter aid ~aterials, or over ion exchange resins, such as described in United States Patent No. ~,177,1~2 or in United States Patent No. 3,250,702, which are assigned to the assignee of this application.
3~ In one broad aspect, the invention relates to a method for removing impurities from a liquid wherein the liquid ' is passed through a filter bed comprising a mixture of treated ' fibrous filter aid material and an active particulate material.
The treated filter aid material and the particulate material have "
',. p~, . , .
, 3 1~29L5~Z
The treated filter aid material and the particulate material have "
',. p~, . , .
, 3 1~29L5~Z
4 --1 opposite surface charges ln aqueous suspension, and the mixture produces a clumping phenomenon, wherein the filter aid material comprises about 5 to 95%, by weight, o. the bed. The filter aid material has been treated with an electrolyte-type compound that produces a surface char~e opposite to the normal surface charge by bondin~ to the surface of the fil~er ~id material.
The invention further provldes an improved filter bed which comprises a mixture of treated fibrous filter aid material and an active particulate material. The treated filter aid material and the particulate material have opposite surface charges in aqueous suspension, and the mixture produces a clump-ing phenomenon wherein the filter aid material comprises about
The invention further provldes an improved filter bed which comprises a mixture of treated fibrous filter aid material and an active particulate material. The treated filter aid material and the particulate material have opposite surface charges in aqueous suspension, and the mixture produces a clump-ing phenomenon wherein the filter aid material comprises about
5 to 95~, by weight, of -the bed. The filter aid material has been treated with an electxolyte-type compound that produces a surface charge opposite to the normal surface charge by bonding to the surface of the filter aid material.
As used herein, the term "bed" refers to a layer, such as a precoat layer, which has been deposited on a filter screen, a wound annular filter cartridge, a film, a deep or shallow bed, or the like. Such a bed may advantageously be deposited on a rubular filter such as described in U.S. Patent No. 3,279,608, which is assigned to the assignee of this application.
More specifically, it has been found that the "clumping" phenomenon described in U.S. Patent No. 3,250,702, .ogether with the advantageous reduced pressure drop and increased filtration efficiency of this phenomenon, can be employed to pass a liquid stream over an active particulate material. -It is well known that most particulate materials normally carry a surface charge in aqueous suspension. By the term "filter aid material,".applicant refers to those materials which are.conventionally deposited on a filter screen or the like in order to aid in the filtration which is produced by the filter. Most such materials are characterized by an electro-negatively charged surface.
The term "fibrous filter aid materials" refers to those having an elongated, fiber-like configuration. The dimensions of these fibers are not critical. However, it is ~ often desirable to control the dimensions to facilitate ,~ ' .
1 precoating onto a filter element. In the case of cellulose, it is preferred that the fibers have a leng-th of about 20 to 1000 microns, and more preferably in the range of 20 to 600 microns. The fiber length may be measured with a microscope having a calibrated, superimposed grid network.
Suitable fibrous filter aid materials which may be used in the present invention include cellulose fibers, poly-acrylonitrile fibers, TeflonR fibers, nylon fibers, rayon fibers, polypropylene fibers, and polyvinyl chloride fibers.
While the particular identity of the fibrous material is not critical, it is important that it normally have a surface charge in aqueous suspension. The particularly preferred fibrous filter aid material for use in accordance with the present invention is cellulose fibers, which is available commercially under the trade mark Solka-Floc.
A wide variety of chemical compounds may be employed in accordance with the present invention in order to produce a reversed surface charge on the fibrous filter aid material.
Such compounds must have a plurality of charge sites so that a hond may be formed with the filter aid material and excess charge sites will remain to produce a surface charge which is the reverse of the normal surface charge.
When the filter aid material normally has an electro-negatively charged surface, a cationic electrolyte-type com-pound is employed, preferably a cationic organic polyelectro-lyte~ These cationic compounds form an electrical bond with the surface of the negatively charged filter aid material, pro-ducing a positive charge on the surface -thereof. Such poly-electrolytes are weil known in the art, and include poly-alkylene imines, polyalkylene polyamines, polyvinylbenzylquaternary ammonium salts,polyvinylbenzyl tertiary amines, vinylbenzyl sulfonium polymers. Specific polymeric compounds that could be employed include, for example, poly(l-butyl-4-vinyl pyridinium bromide), and poly( 1,2-dimethyl-5-vinyl pyridinium sulfate). A particularly suitable cationic poly-amine is one characterized by the repeating structure:
. . f ~.~
z - _ 6 CH2 - CH _ `~h" Cl ` CH3 The application of chemical compounds to the filter 2iCS in order to produce a reverse surface charge is normally carried out in aqueous suspension. In carrying out the pre-ferred method, the filter aid material is simply suspended in s ~ater, and an adequate amount of chemical compound is added to produce the desired reverse surface charge. With high molecu-lar weight polyelectrolytes (i.e., molecular weights in excess of 100,000), the point at which adequate polyelectrolyte has been added can be determined by observing the filter aid 0 material as the polyelectrolyte is added. Initially, clumping will be produced as the surface charge of a portion of the fibers is reversed, and this clumping will then disappear when a reversal of substantially all of the surface charge is o'~served. However, with lower molecular weight polyelectrolytes, :5 and even with some combinations of high molecular weight p~lyelectrolytes and filter aid material, no noticeable clump-ing Is prod~ced when the polyelectrolyte is added. In those i~stances, an adequate amollnt o polyelectrolyte must be ,. , determined from the results obtained when the treated fibers ' ~ 20 are mixed with the active particulate material. In general, , at least about 5% of the chemical compound, based upon the weight of the dry filter aid particles, is requir~ed. However, - much larger amounts can be employed, as there is no detriment realized from the use of an excess amount of the sur~ace 2; ch~rge reversal-producing compound. Of course, the amount o . .. ~ . . .
~; compound required in a particular case depends upon many ~' ,~actors, including the nature of the fibers being treated and ,?,~ the number of positive or negative sites that are available on the chemical compound being added.
' ... .
~ ~ - 7 -`,;
1 After the foregoing treatment has been completed, the filter aid material is normally de-watered and dried, and is ~` then resuspended in water when it is desired to combine it with an active particulate material to form a Eilter bed.
In most instances, the fibrous filter aid material and the active particulate material will both normally have a negative sur~ace charge in aqueous suspension. In those cases, the filter aid will be treated with a cationic electrolyte-type compound to produce a positive surface charge, as previously described.
In some instances, the filter aid material, the active particulate material, or both, may normally have a positive surface charge. Bearing in mind that the objective is to obtain an opposite charge between the fibrous filter aid material and the active particulate material, modifieations of this treatment becomes neeessary. Thus, where both the fibrous filter aid material and the active partieulate material are positively charged, the filter aid material must be treated with an anionic electrolyte-type compound to produce an electro-negative surface charge. Suitable anionic compounds include polymeric acids such as polyacrylic acids, polysulphonic acids.
The method of treatment is the same as thatldescribed;above in connection with the application of cationic materials.
In those instances where the fibrous filter aid material and the active particulate material normally have opposite surface charges in aqueous suspension, it is necessary to further treat the filter aid material with a second electrolyte-type compound to produce an enhanced surface charge which is the same as the normal surface charge. This enhanced eharge is produced when the second electrolyte-type compound bonds to the treated filter aid material.
Thus, when the fibrous filter aid material normally has a negative surface charge in aqueous suspension, while the active particulate material has a positive charge, a "double treatment" o~ the filter aid material is employed to produce an enhanced electro-negative surface charge. To carry out :
i' 1 ~h s double treatment,'the fibrous filter aid material is -i-st treated with a cationic electrolyte-type compound as pr2viously described to produce a positive charge. The treated ~ilter aid material is then treated in the same manner with an an onic electrolyte-type compound to re-reverse the charge, producing an enhanced electronegative surface charge. Of course, in the opposite situation, where the filter aid mater-ia' has a positive charge and the active particulate material ~.as a negative charge, the "double treatment" would be reversed.
10 rhat is, the filter aid material would be first treated with zn anionic electrolyte-type compound and then with a cationic electrolyte-type compound to produce an enhanced electropositive su~face charge.
As previously mentioned, a wide variety of active particulate materials may be utilized in accordance with the present invention. Examples include activated carbon, adsorp-tive clays such as bentonite; molecular sieves such as zeolite;
zirconium oxides'; zirconium phosphate; iron sulfi.de; and diatomaceous earth. Synthetic adsorbants may also be employed, 20 such as those marketed by Rohm and Haas Co. under the trademark ~berlite XAD. Activated al~mina may also be employed, al-though it should be borne in mind that, unlike the active particulate materials exemplified above, activated alumina has G positive surface charge in aqueous suspension.
r'5 ' 'The particle size of the active partlculate material ~'-1 depend upon the particular material being employed. For excm?le, in'the case of activated carbon, it is desirable to ha~e very small`particle size in order to maximize the surface z-ea. I~hen it is desired to maximize surface area, particles 30 25 small as one micron average particle size may be employed i~ accordance with the present invention. However, it should be understood that the present invention is operative with ch larger particles, as large as 300 microns average particle aiz~eter. ' After this mixture of fibrous filter aid material znc active particulate material has been prepared, it may be deposited on a filter element or other suitable support to ~ ~ - 9 -1 form a bed. Alternatively, the mixture may be dewatered or dried and later resuspended prior to being deposited.
~ hile the fibrous filter aid material may generally form as much as 95% or as little as 5% o~ the fiiter bed, on a dry weight basis, it is preferred tha~ this material comprise from about 25% to about 60% of the bed. It should also be understood that, while the method and filter bed of the present invention will ordinarily employ a single fibrous filter aid material in combination with a single active particulate material, combinations of either or both materials may be employed in order to tailor the properties of the bed to a particular need.
The following examples are intended to illustrate the present invention, and should not be construed as limita-tive, the scope of the invention being determined by the ap-pended claims.
In Examples I through V, the tests referred to were all conducted in a filter element having a single, tubular, stainless steel filter element having a layer of 8 mesh stain-less steel screen covered by a layer of 50 x 250 mesh stain-less steel screen, and having a surface area of .39 Ft.2. The filter element was precoated with the precoat material being employed by recirculating a slurry of the material through the element until a clear recycle stream was produced, indicating that all of the precoat material was deposited on the filter.
l~ith the amount of material employed, this procedure produced a uniform precoat having a depth of about 1/4 inch.
EXAMPLE I
17.7 grams of cellulose fibers, having an average length of 96 microns and an average diameter of 17 microns, were suspended in about 500 ml. of demineralized water in a tank equip~ed with a mechanical stirrer. 5.3 ml. of a 10%
solution of cationic polyelectrolyte was added, and stirring was continued for ten minutes. The cationic polyelectrolyte employed was a commercially available polyamide having a molecular weight in the range of 20,000 to 100,000. This S;~
.~ - 10 -1 polyelectrolyte is available commercially under the trade mark "Betz 1175," sold by the Betz Company, Trevose, Pennsylvania.
After ten minutes of stirring, 17.7 gra~.s finely divided activated carbon, having an average particle diame~er of less than 20 microns, was added. Stirring ~as continued for 10 minutes, and the final slurry was precoated onto the filter element described above. The amount of precoat mat~r-ial resulted in a coverage of 0.2 lb./ft.2 In order to test the ability of the activated 10 carbon/fiber precoat to absorb chlorine from aqueous solution, 25 ml. of a 5% solution of sodium hypochlorite (iNaOCl) was added to 25 liters demineralized water in a feed tank. The tank was pressurized to 40 psig using purified nitrogen. This solution was metered into the influent line and through the 15 filter at a flow rate of approximately 50 ml./min., resulting in a chlorine feed concentration of 1 ppm. + 10%. The flow rate through the fil~er bed was 2.0 gpm/ft.2 Free chlorine in the effluent stream was determined using a test kit which relies on the reaction of free chlorine with ~,N-diethyl-p-20 phenylenediamine to produce a rose color. The results are shown in the following table:
.
_ Time (hr) Effluent Co~c./Influent Conc.
<0.1 2.5 <0.1 7 ~0.1 12.5 <0.1 19 0.05 23.5 Q.2 0.3 36 0.4 ~.~4~5~
1 ~ EXAMPLE II
Example I was repeated except that the amount ofprecoat material was doubled to produce a coverage of 0.4 lb./ft.2 on the filter element. The results are shown below in Table 2.
Table 2 Time (hr.) Effluent Conc./Influent Conc.
1.0 <0.1
As used herein, the term "bed" refers to a layer, such as a precoat layer, which has been deposited on a filter screen, a wound annular filter cartridge, a film, a deep or shallow bed, or the like. Such a bed may advantageously be deposited on a rubular filter such as described in U.S. Patent No. 3,279,608, which is assigned to the assignee of this application.
More specifically, it has been found that the "clumping" phenomenon described in U.S. Patent No. 3,250,702, .ogether with the advantageous reduced pressure drop and increased filtration efficiency of this phenomenon, can be employed to pass a liquid stream over an active particulate material. -It is well known that most particulate materials normally carry a surface charge in aqueous suspension. By the term "filter aid material,".applicant refers to those materials which are.conventionally deposited on a filter screen or the like in order to aid in the filtration which is produced by the filter. Most such materials are characterized by an electro-negatively charged surface.
The term "fibrous filter aid materials" refers to those having an elongated, fiber-like configuration. The dimensions of these fibers are not critical. However, it is ~ often desirable to control the dimensions to facilitate ,~ ' .
1 precoating onto a filter element. In the case of cellulose, it is preferred that the fibers have a leng-th of about 20 to 1000 microns, and more preferably in the range of 20 to 600 microns. The fiber length may be measured with a microscope having a calibrated, superimposed grid network.
Suitable fibrous filter aid materials which may be used in the present invention include cellulose fibers, poly-acrylonitrile fibers, TeflonR fibers, nylon fibers, rayon fibers, polypropylene fibers, and polyvinyl chloride fibers.
While the particular identity of the fibrous material is not critical, it is important that it normally have a surface charge in aqueous suspension. The particularly preferred fibrous filter aid material for use in accordance with the present invention is cellulose fibers, which is available commercially under the trade mark Solka-Floc.
A wide variety of chemical compounds may be employed in accordance with the present invention in order to produce a reversed surface charge on the fibrous filter aid material.
Such compounds must have a plurality of charge sites so that a hond may be formed with the filter aid material and excess charge sites will remain to produce a surface charge which is the reverse of the normal surface charge.
When the filter aid material normally has an electro-negatively charged surface, a cationic electrolyte-type com-pound is employed, preferably a cationic organic polyelectro-lyte~ These cationic compounds form an electrical bond with the surface of the negatively charged filter aid material, pro-ducing a positive charge on the surface -thereof. Such poly-electrolytes are weil known in the art, and include poly-alkylene imines, polyalkylene polyamines, polyvinylbenzylquaternary ammonium salts,polyvinylbenzyl tertiary amines, vinylbenzyl sulfonium polymers. Specific polymeric compounds that could be employed include, for example, poly(l-butyl-4-vinyl pyridinium bromide), and poly( 1,2-dimethyl-5-vinyl pyridinium sulfate). A particularly suitable cationic poly-amine is one characterized by the repeating structure:
. . f ~.~
z - _ 6 CH2 - CH _ `~h" Cl ` CH3 The application of chemical compounds to the filter 2iCS in order to produce a reverse surface charge is normally carried out in aqueous suspension. In carrying out the pre-ferred method, the filter aid material is simply suspended in s ~ater, and an adequate amount of chemical compound is added to produce the desired reverse surface charge. With high molecu-lar weight polyelectrolytes (i.e., molecular weights in excess of 100,000), the point at which adequate polyelectrolyte has been added can be determined by observing the filter aid 0 material as the polyelectrolyte is added. Initially, clumping will be produced as the surface charge of a portion of the fibers is reversed, and this clumping will then disappear when a reversal of substantially all of the surface charge is o'~served. However, with lower molecular weight polyelectrolytes, :5 and even with some combinations of high molecular weight p~lyelectrolytes and filter aid material, no noticeable clump-ing Is prod~ced when the polyelectrolyte is added. In those i~stances, an adequate amollnt o polyelectrolyte must be ,. , determined from the results obtained when the treated fibers ' ~ 20 are mixed with the active particulate material. In general, , at least about 5% of the chemical compound, based upon the weight of the dry filter aid particles, is requir~ed. However, - much larger amounts can be employed, as there is no detriment realized from the use of an excess amount of the sur~ace 2; ch~rge reversal-producing compound. Of course, the amount o . .. ~ . . .
~; compound required in a particular case depends upon many ~' ,~actors, including the nature of the fibers being treated and ,?,~ the number of positive or negative sites that are available on the chemical compound being added.
' ... .
~ ~ - 7 -`,;
1 After the foregoing treatment has been completed, the filter aid material is normally de-watered and dried, and is ~` then resuspended in water when it is desired to combine it with an active particulate material to form a Eilter bed.
In most instances, the fibrous filter aid material and the active particulate material will both normally have a negative sur~ace charge in aqueous suspension. In those cases, the filter aid will be treated with a cationic electrolyte-type compound to produce a positive surface charge, as previously described.
In some instances, the filter aid material, the active particulate material, or both, may normally have a positive surface charge. Bearing in mind that the objective is to obtain an opposite charge between the fibrous filter aid material and the active particulate material, modifieations of this treatment becomes neeessary. Thus, where both the fibrous filter aid material and the active partieulate material are positively charged, the filter aid material must be treated with an anionic electrolyte-type compound to produce an electro-negative surface charge. Suitable anionic compounds include polymeric acids such as polyacrylic acids, polysulphonic acids.
The method of treatment is the same as thatldescribed;above in connection with the application of cationic materials.
In those instances where the fibrous filter aid material and the active particulate material normally have opposite surface charges in aqueous suspension, it is necessary to further treat the filter aid material with a second electrolyte-type compound to produce an enhanced surface charge which is the same as the normal surface charge. This enhanced eharge is produced when the second electrolyte-type compound bonds to the treated filter aid material.
Thus, when the fibrous filter aid material normally has a negative surface charge in aqueous suspension, while the active particulate material has a positive charge, a "double treatment" o~ the filter aid material is employed to produce an enhanced electro-negative surface charge. To carry out :
i' 1 ~h s double treatment,'the fibrous filter aid material is -i-st treated with a cationic electrolyte-type compound as pr2viously described to produce a positive charge. The treated ~ilter aid material is then treated in the same manner with an an onic electrolyte-type compound to re-reverse the charge, producing an enhanced electronegative surface charge. Of course, in the opposite situation, where the filter aid mater-ia' has a positive charge and the active particulate material ~.as a negative charge, the "double treatment" would be reversed.
10 rhat is, the filter aid material would be first treated with zn anionic electrolyte-type compound and then with a cationic electrolyte-type compound to produce an enhanced electropositive su~face charge.
As previously mentioned, a wide variety of active particulate materials may be utilized in accordance with the present invention. Examples include activated carbon, adsorp-tive clays such as bentonite; molecular sieves such as zeolite;
zirconium oxides'; zirconium phosphate; iron sulfi.de; and diatomaceous earth. Synthetic adsorbants may also be employed, 20 such as those marketed by Rohm and Haas Co. under the trademark ~berlite XAD. Activated al~mina may also be employed, al-though it should be borne in mind that, unlike the active particulate materials exemplified above, activated alumina has G positive surface charge in aqueous suspension.
r'5 ' 'The particle size of the active partlculate material ~'-1 depend upon the particular material being employed. For excm?le, in'the case of activated carbon, it is desirable to ha~e very small`particle size in order to maximize the surface z-ea. I~hen it is desired to maximize surface area, particles 30 25 small as one micron average particle size may be employed i~ accordance with the present invention. However, it should be understood that the present invention is operative with ch larger particles, as large as 300 microns average particle aiz~eter. ' After this mixture of fibrous filter aid material znc active particulate material has been prepared, it may be deposited on a filter element or other suitable support to ~ ~ - 9 -1 form a bed. Alternatively, the mixture may be dewatered or dried and later resuspended prior to being deposited.
~ hile the fibrous filter aid material may generally form as much as 95% or as little as 5% o~ the fiiter bed, on a dry weight basis, it is preferred tha~ this material comprise from about 25% to about 60% of the bed. It should also be understood that, while the method and filter bed of the present invention will ordinarily employ a single fibrous filter aid material in combination with a single active particulate material, combinations of either or both materials may be employed in order to tailor the properties of the bed to a particular need.
The following examples are intended to illustrate the present invention, and should not be construed as limita-tive, the scope of the invention being determined by the ap-pended claims.
In Examples I through V, the tests referred to were all conducted in a filter element having a single, tubular, stainless steel filter element having a layer of 8 mesh stain-less steel screen covered by a layer of 50 x 250 mesh stain-less steel screen, and having a surface area of .39 Ft.2. The filter element was precoated with the precoat material being employed by recirculating a slurry of the material through the element until a clear recycle stream was produced, indicating that all of the precoat material was deposited on the filter.
l~ith the amount of material employed, this procedure produced a uniform precoat having a depth of about 1/4 inch.
EXAMPLE I
17.7 grams of cellulose fibers, having an average length of 96 microns and an average diameter of 17 microns, were suspended in about 500 ml. of demineralized water in a tank equip~ed with a mechanical stirrer. 5.3 ml. of a 10%
solution of cationic polyelectrolyte was added, and stirring was continued for ten minutes. The cationic polyelectrolyte employed was a commercially available polyamide having a molecular weight in the range of 20,000 to 100,000. This S;~
.~ - 10 -1 polyelectrolyte is available commercially under the trade mark "Betz 1175," sold by the Betz Company, Trevose, Pennsylvania.
After ten minutes of stirring, 17.7 gra~.s finely divided activated carbon, having an average particle diame~er of less than 20 microns, was added. Stirring ~as continued for 10 minutes, and the final slurry was precoated onto the filter element described above. The amount of precoat mat~r-ial resulted in a coverage of 0.2 lb./ft.2 In order to test the ability of the activated 10 carbon/fiber precoat to absorb chlorine from aqueous solution, 25 ml. of a 5% solution of sodium hypochlorite (iNaOCl) was added to 25 liters demineralized water in a feed tank. The tank was pressurized to 40 psig using purified nitrogen. This solution was metered into the influent line and through the 15 filter at a flow rate of approximately 50 ml./min., resulting in a chlorine feed concentration of 1 ppm. + 10%. The flow rate through the fil~er bed was 2.0 gpm/ft.2 Free chlorine in the effluent stream was determined using a test kit which relies on the reaction of free chlorine with ~,N-diethyl-p-20 phenylenediamine to produce a rose color. The results are shown in the following table:
.
_ Time (hr) Effluent Co~c./Influent Conc.
<0.1 2.5 <0.1 7 ~0.1 12.5 <0.1 19 0.05 23.5 Q.2 0.3 36 0.4 ~.~4~5~
1 ~ EXAMPLE II
Example I was repeated except that the amount ofprecoat material was doubled to produce a coverage of 0.4 lb./ft.2 on the filter element. The results are shown below in Table 2.
Table 2 Time (hr.) Effluent Conc./Influent Conc.
1.0 <0.1
6.5 ~0.1 10.5 ~0.1 19.0 <0.1 1~ 26.0 36.0 ~0.1 43 <0.1 ~0.1 ' ' ~0.1 69 0.05 0.075 71 ' 0.1 As the data of Tables 1 and 2 demonst-ate, the method 25and filter-material of the present,invention are highly effective in removing chlorine from aqueous solution. Moreover~ the run length was more than doubled by doubling the amount of the filter bed on the element.
EXAMPLE III
In the following example, a filter material prepared in accordance with the present invention was evaluated for the removal of an organic contaminant, o-chlorophenol, from aqueous solution. -17.7 grams of the same cellulose fibers employed in the previous examples was suspended in 500 ml. demineralized water and 2 ml. of a 1% solution of a cationic polyelectrolyte ~2 1 was added.. This polyelectrolyte was a co~mercially available polyamine having a molecular weight in excess of one million.
It is marketed by Rohm and Haas under the trade m~rk "Primafloc C-7." Stirring was continued for 15 minutes, and the material as then dewatered on a Buchner funnel using a I~JhatmanTM No. 451 filter paper. The dewatered slurry was rinsed with 500 ml.
demineralized water and resuspended in 450 ml. demineralized .~ater. 17.7 grams of the same activated carbon used in the preceding examples was added, and stirring was continued for 10 10 minutes. The precoat was coated onto a filter cartridge in an amount sufficient to give a depth of 1/4 inch and a loading of 0.2 lb./ft.
An aqueous solution of o-chlorophenol having a concen-tration of approximately 1 ppm. was fed through the filter 15 element at varying flow rates. The effluent was analyzed for o-chlorophenol using ASTM method AD 1783-70. The following results were obtained:
(flow rate.of 2 gpm/ft. ) Time (hrs.) Effluent Concentration ppm 0.25 0.0027 , 0.75 0.005 1.5 0.003 2.0 0.002 2.5 0.006 3.25 0.004 O 3.75 O.OC32 4 5 0.0067 5.0 0.005 5 3 0.0205 5.5 0.0325 .~ ~
.
s~
i TABLE 4 (flow rate of 4 gpm/ft.2) Time (hrs.) Effluent Concentration ppm -0.5 0.00 1.0 ` 1.5 0.003 2.0 0.0098 C 2.5 0.038 3 0 0.085 ~,5 (flow rate of 6 gpm/ft. ) Time (hrs.) Effluent Concentration ppm 0 33 0.002 _ O O . O O
0.67 0 003 0.83 0 003 .o 0.0065 1.2 0.008 :, 1.3 0.0095 1.7 0.035 As can be seen, the method of the present invention ~.as highly effective in removing o-chlorophenol from aqueous 30 solution.
EXAMPLE IV
The following example was conducted to demonstrate the articulate filtration ability, or "crud capacity," of the 35 ~e~hod and filter bed of the present invention. A filter mater-ial was prepared and precoated onto a filter element as in .
: ~ .
~ ' .
s~
1 Example III. In this instance, a 1 ppm. suspension of Fe203 was fed through the filter element at a flow rate of 4.0 gpm/ft. , and effluent Fe203 concentration was measured periodically using a millipore filter. The results are shown below in Table 6.
Crud Loading (lb- Fe203/lb. Precoat)Pressure Drop (p5i) 0 ~1.0 0.0~ ~ 1.0 0.15 2.0 0.19 5.0 0.23 7.0 ` 0.25 12.0 0.27 20.0 0.28 - 25.0 It can be seen that filter beds prepared in accordance with the present invention exhibit an excellent ability to remoYe suspended materials from aqueous suspension at low pres-sure-drop levels. This is particularly significant in the case of Fe203, which is an especially difficult ma~erial to remove from aqueous suspension.
EXAMPLE V
In order to obtain a comparison with activated carbon alone, an attempt was made to precoat a filter element with activated carbon in order to determine the filtration character-istics of this material. 35.4 g. activated carbon were sus-pended in 7 1. demineralized water using a mechanical stirrer as before. However, when an attempt was made to precoat this material onto the filter element, the pressure drop rose rapidly to a level in excess of 20 psi. It was estimated that less than half of the activated carbon had been precoated onto the filter element at this point. At this high pressure drop level, any filtration test ~ou~d have exceeded the capacity of the pump, . .
", ,i 1 and the filter element could be considered to be effectively completely blocked. This experiment thus demonstrated that activated carbon alone cannot be used in accordance with the present invention.
EXAMPLE VI
In order to demonstrate the feasibility of the method ; and filter bed of the present invention with other active particulate materials and other fibrous filter aid materials, the following experiments were conducted. In each instance, ; 10 26.6 g. of the fibrous filter aid material was suspended in 500 ml. demineraliYed water, and 8.0 ml. of a 10% solution of the same cationic organic polyelectrolyte used in the preceeding examples was added. Stirring was continued for ten minutes, the " slurry was allowed to settle for 15 minutes, and the supernate was decanted. 8.8 g. of the active particulate material was added and the suspension was stirred for another 5 minutes. For comparison purposes, the identical test was repeated in each instance, except that the fibrous filter aid material was not treated with an organic polyelectrolyte.
Through a vast amount of experience with commercial processes, it is known that the ability of the mixture to form a filter bed which gives a desirably low pressure drop together with eficient "in-depth" filtration may be determined by making a volume measurement referred to as "V/V15." This measurement is made by transferring a slurry having a 7% solids concentra-tion, by weight, to a 500 ml. graduate and allowing the material to settle for 15 minutes. The ratio of settled floc to total volume (500 ml.) is reported as V/V15. The turbidity of the supernatant also provides a measure of the efficiency of "clump-ing" in that, when agglomeration occurs, fines will be removedfrom the supernate. Thus, the lo~er the supernatant turbidity, -. the better the filter that is formed. The turbidity measurements set forth in the following~table were made by withdrawing a 50 ;ml. sample from the supernatant and measuring it on a Hach turbi-. 35 dimeter Model 1720. In cases where it was impossible to remove , a 50 ml. sample, the turbidity was estimated by comparison with a set o~ turbidity standards supplied by the Hach Manufacturing Company. The results are shown below in Table 7.
~"
~,' .
~, ,, .
. . ..
1~4Z~SZ
o o o o o ~ o o o o o J- O O O O O
td ~ ~ ~ ~ ~
.. ~' ~ ~
E~ 1~
H
P
~q ~a 1:~ a) ooooo ~ ~ O ~ ~ ~1 ~
~ ~ ~ ~ ? ~
r .
C~
U~
h ,_ a r~
a~
~4 ¢
E~
a~ a) J , ~ U
L"
E~ u~
O O o U~
i~ .5 ~ ~ JJ
~ ~ P~
H
¢ ~1 C .C ,C~ ,C ,C:
O ~ O O ~
c J_l ~1 '~) ~) C) ~a ~ ~ ~ O
H
¢ U
~J
aJ
E~ CJ
H u~
o o o o a~
u~ H ~ ~ :~ h :~ ¢ ~ ~ ~ ~ O
o ~ ~1 ~ ~ ~ Z;
~ a) a~ Q) O ~
H C~ Z -.`C
~, ~l~L4Z~5Z
.
1 As all of the foregoing data demonstrate, satis-~actory precoats could be formed from any of the combinations set forth above where the fibrous filter aid was treated with a cationic polyelectrolyte. In contrast the mixture prepared with untreated fibrous filter aid would not form a satisfactory precoat.
EXAMPLE VII
Example VI was repeated, except that, in this instance, the active particulate material employed was alunina, which has a positive surface charge in aqueous suspension. It was there-fore necessary to provide a "double treatment" to the fibrous rilter aid material, which has a negative surface charge in aqueous suspension. In order to accomplish this double treat-~ent, after the addition of cationic polyelectrolyte as in theforegoing example, and after the cellulose slurry was allowed to mix for ten minutes, 8.0 ml. of a 10% solution of poly-acrylic acid having a molecular weight in the îange of 150,000-300,000 was added, and mixing was continued for ten minutes more. At the completion of mixing, the slurry was allowed to settle for 15 minutes and the supernatant was decanted as in the previous example. 8.8 g. powdered activated alumina, having a particle size of less than 10 microns was added. The data are shown below in Table 8.
~ ~ .
S;Z
o aJ o o E~ ~
Z ~g a P~ ~ o o :~
E~ E~
a) a~ o ~ ,~
~1 ~ . .
aJ
CO ~ C`l ~ .~
E¢~
=~
E~
;1 S:~
E~ ,~
rl~ ~ , ~ ¢
E
H .
a a ~n .
U~ ~ o ¢
~o ~ C~
' :
:
~ ~ ~ Z ~ 5 Again, the foregoing data demonstrate that a satis-factory precoat material could be prepared from this combina-tion when the fibrous filter aid material is first treated in accordance with the present invention. Thus, filtration could be achieved while the desired absorptive properties of activated alu~ina would be realized.
Obviously, many modifications and variations of the invention as hereinbefore set forth will occur to those skilled in the art, and it is intended to cover in the appended claims 10 all such modifications and variations as fall within the true s?irit and scope of the invention.
EXAMPLE III
In the following example, a filter material prepared in accordance with the present invention was evaluated for the removal of an organic contaminant, o-chlorophenol, from aqueous solution. -17.7 grams of the same cellulose fibers employed in the previous examples was suspended in 500 ml. demineralized water and 2 ml. of a 1% solution of a cationic polyelectrolyte ~2 1 was added.. This polyelectrolyte was a co~mercially available polyamine having a molecular weight in excess of one million.
It is marketed by Rohm and Haas under the trade m~rk "Primafloc C-7." Stirring was continued for 15 minutes, and the material as then dewatered on a Buchner funnel using a I~JhatmanTM No. 451 filter paper. The dewatered slurry was rinsed with 500 ml.
demineralized water and resuspended in 450 ml. demineralized .~ater. 17.7 grams of the same activated carbon used in the preceding examples was added, and stirring was continued for 10 10 minutes. The precoat was coated onto a filter cartridge in an amount sufficient to give a depth of 1/4 inch and a loading of 0.2 lb./ft.
An aqueous solution of o-chlorophenol having a concen-tration of approximately 1 ppm. was fed through the filter 15 element at varying flow rates. The effluent was analyzed for o-chlorophenol using ASTM method AD 1783-70. The following results were obtained:
(flow rate.of 2 gpm/ft. ) Time (hrs.) Effluent Concentration ppm 0.25 0.0027 , 0.75 0.005 1.5 0.003 2.0 0.002 2.5 0.006 3.25 0.004 O 3.75 O.OC32 4 5 0.0067 5.0 0.005 5 3 0.0205 5.5 0.0325 .~ ~
.
s~
i TABLE 4 (flow rate of 4 gpm/ft.2) Time (hrs.) Effluent Concentration ppm -0.5 0.00 1.0 ` 1.5 0.003 2.0 0.0098 C 2.5 0.038 3 0 0.085 ~,5 (flow rate of 6 gpm/ft. ) Time (hrs.) Effluent Concentration ppm 0 33 0.002 _ O O . O O
0.67 0 003 0.83 0 003 .o 0.0065 1.2 0.008 :, 1.3 0.0095 1.7 0.035 As can be seen, the method of the present invention ~.as highly effective in removing o-chlorophenol from aqueous 30 solution.
EXAMPLE IV
The following example was conducted to demonstrate the articulate filtration ability, or "crud capacity," of the 35 ~e~hod and filter bed of the present invention. A filter mater-ial was prepared and precoated onto a filter element as in .
: ~ .
~ ' .
s~
1 Example III. In this instance, a 1 ppm. suspension of Fe203 was fed through the filter element at a flow rate of 4.0 gpm/ft. , and effluent Fe203 concentration was measured periodically using a millipore filter. The results are shown below in Table 6.
Crud Loading (lb- Fe203/lb. Precoat)Pressure Drop (p5i) 0 ~1.0 0.0~ ~ 1.0 0.15 2.0 0.19 5.0 0.23 7.0 ` 0.25 12.0 0.27 20.0 0.28 - 25.0 It can be seen that filter beds prepared in accordance with the present invention exhibit an excellent ability to remoYe suspended materials from aqueous suspension at low pres-sure-drop levels. This is particularly significant in the case of Fe203, which is an especially difficult ma~erial to remove from aqueous suspension.
EXAMPLE V
In order to obtain a comparison with activated carbon alone, an attempt was made to precoat a filter element with activated carbon in order to determine the filtration character-istics of this material. 35.4 g. activated carbon were sus-pended in 7 1. demineralized water using a mechanical stirrer as before. However, when an attempt was made to precoat this material onto the filter element, the pressure drop rose rapidly to a level in excess of 20 psi. It was estimated that less than half of the activated carbon had been precoated onto the filter element at this point. At this high pressure drop level, any filtration test ~ou~d have exceeded the capacity of the pump, . .
", ,i 1 and the filter element could be considered to be effectively completely blocked. This experiment thus demonstrated that activated carbon alone cannot be used in accordance with the present invention.
EXAMPLE VI
In order to demonstrate the feasibility of the method ; and filter bed of the present invention with other active particulate materials and other fibrous filter aid materials, the following experiments were conducted. In each instance, ; 10 26.6 g. of the fibrous filter aid material was suspended in 500 ml. demineraliYed water, and 8.0 ml. of a 10% solution of the same cationic organic polyelectrolyte used in the preceeding examples was added. Stirring was continued for ten minutes, the " slurry was allowed to settle for 15 minutes, and the supernate was decanted. 8.8 g. of the active particulate material was added and the suspension was stirred for another 5 minutes. For comparison purposes, the identical test was repeated in each instance, except that the fibrous filter aid material was not treated with an organic polyelectrolyte.
Through a vast amount of experience with commercial processes, it is known that the ability of the mixture to form a filter bed which gives a desirably low pressure drop together with eficient "in-depth" filtration may be determined by making a volume measurement referred to as "V/V15." This measurement is made by transferring a slurry having a 7% solids concentra-tion, by weight, to a 500 ml. graduate and allowing the material to settle for 15 minutes. The ratio of settled floc to total volume (500 ml.) is reported as V/V15. The turbidity of the supernatant also provides a measure of the efficiency of "clump-ing" in that, when agglomeration occurs, fines will be removedfrom the supernate. Thus, the lo~er the supernatant turbidity, -. the better the filter that is formed. The turbidity measurements set forth in the following~table were made by withdrawing a 50 ;ml. sample from the supernatant and measuring it on a Hach turbi-. 35 dimeter Model 1720. In cases where it was impossible to remove , a 50 ml. sample, the turbidity was estimated by comparison with a set o~ turbidity standards supplied by the Hach Manufacturing Company. The results are shown below in Table 7.
~"
~,' .
~, ,, .
. . ..
1~4Z~SZ
o o o o o ~ o o o o o J- O O O O O
td ~ ~ ~ ~ ~
.. ~' ~ ~
E~ 1~
H
P
~q ~a 1:~ a) ooooo ~ ~ O ~ ~ ~1 ~
~ ~ ~ ~ ? ~
r .
C~
U~
h ,_ a r~
a~
~4 ¢
E~
a~ a) J , ~ U
L"
E~ u~
O O o U~
i~ .5 ~ ~ JJ
~ ~ P~
H
¢ ~1 C .C ,C~ ,C ,C:
O ~ O O ~
c J_l ~1 '~) ~) C) ~a ~ ~ ~ O
H
¢ U
~J
aJ
E~ CJ
H u~
o o o o a~
u~ H ~ ~ :~ h :~ ¢ ~ ~ ~ ~ O
o ~ ~1 ~ ~ ~ Z;
~ a) a~ Q) O ~
H C~ Z -.`C
~, ~l~L4Z~5Z
.
1 As all of the foregoing data demonstrate, satis-~actory precoats could be formed from any of the combinations set forth above where the fibrous filter aid was treated with a cationic polyelectrolyte. In contrast the mixture prepared with untreated fibrous filter aid would not form a satisfactory precoat.
EXAMPLE VII
Example VI was repeated, except that, in this instance, the active particulate material employed was alunina, which has a positive surface charge in aqueous suspension. It was there-fore necessary to provide a "double treatment" to the fibrous rilter aid material, which has a negative surface charge in aqueous suspension. In order to accomplish this double treat-~ent, after the addition of cationic polyelectrolyte as in theforegoing example, and after the cellulose slurry was allowed to mix for ten minutes, 8.0 ml. of a 10% solution of poly-acrylic acid having a molecular weight in the îange of 150,000-300,000 was added, and mixing was continued for ten minutes more. At the completion of mixing, the slurry was allowed to settle for 15 minutes and the supernatant was decanted as in the previous example. 8.8 g. powdered activated alumina, having a particle size of less than 10 microns was added. The data are shown below in Table 8.
~ ~ .
S;Z
o aJ o o E~ ~
Z ~g a P~ ~ o o :~
E~ E~
a) a~ o ~ ,~
~1 ~ . .
aJ
CO ~ C`l ~ .~
E¢~
=~
E~
;1 S:~
E~ ,~
rl~ ~ , ~ ¢
E
H .
a a ~n .
U~ ~ o ¢
~o ~ C~
' :
:
~ ~ ~ Z ~ 5 Again, the foregoing data demonstrate that a satis-factory precoat material could be prepared from this combina-tion when the fibrous filter aid material is first treated in accordance with the present invention. Thus, filtration could be achieved while the desired absorptive properties of activated alu~ina would be realized.
Obviously, many modifications and variations of the invention as hereinbefore set forth will occur to those skilled in the art, and it is intended to cover in the appended claims 10 all such modifications and variations as fall within the true s?irit and scope of the invention.
Claims (20)
1. A method for removing impurities from a liquid comprising: passing said liquid through a filter bed comprising a mixture of treated fibrous filter aid material and an active particulate material, said treated filter aid material and said particulate material having opposite surface charges in aqueous suspension, and said mixture producing a clumping phenomenon, wherein said filter aid material comprises about 5 to 95%, by weight, of said bed, and wherein said filter aid material has been treated with an electrolyte-type compound that produces a surface charge opposite to the normal surface charge by bonding to the surface of said filter aid material.
2. The method as defined in claim 1 wherein said active particulate material is selected from the group consisting of organic polymeric absorbants, zeolites, bentonite, zirconium oxide, zirconium phosphate, activated alumina, ferrous sulfide, activated carbon, and diatomaceous earth.
3. The method as defined in claim 2 wherein said filter aid material is selected from the group consisting of cellulose fibers, polyacrylonitrile fibers, TeflonTM fibers, nylon fibers, rayon fibers, polypropylene fibers and polyvinyl chloride fibers.
4. The method as defined in claim 3 wherein the fibers of said filter aid material have an average length of from about 10 to about 1000 microns.
5. The method as defined in claim 1 wherein said active particulate material is activated carbon.
6. The method as defined in claim 1 wherein said filter aid material has been further treated with a second electrolyte-type compound to produce an enhanced surface charge which is the same as said normal surface charge by bonding to said treated filter aid material.
7. The method as defined in Claim 6 wherein said filter aid material normally has a negative charge in aqueous suspension.
8. A method for removing impurities from a liquid comprising: passing said liquid through a filter bed comprising a mixture of treated cellulose fibers and activated carbon particles, said carbon particles having a negative surface charge, and said mixture producing a clumping phenomenon, wherein said cellulose fibers comprise about 5 to 95%, by weight, of said bed, and wherein said cellulose fibers have been treated with an electrolyte-type compound that produces a positive surface charge by bonding to the surface of said fibers.
9. The method as defined in claim 6 wherein said electrolyte-type compound is a cationic organic polyelectro-lyte.
10. The method as defined in claim 8 wherein said cellulose fibers comprise about 25 to 60%, by weight, of said bed.
11. An improved filter bed comprising a mixture of treated fibrous filter aid material and an active particulate material, said treated filter aid material and said particulate material having opposite surface charges in aqueous suspension, and said mixture producing a clumping phenomenon, wherein said filter aid material comprises about 5 to 95%, by weight, of said bed, and wherein said filter aid material has been treated with an electrolyte-type compound that produces a surface charge opposite to the normal surface charge by bonding to the surface of said filter aid material.
12. The filter bed as defined in Claim 11 wherein said active particulate material is selected from the group consisting of organic polymeric absorbants, zeolites, bento-nite, zirconium oxide, zirconium phosphate, activated alumina, ferrous sulfide, activated carbon, and diatomaceous earth.
13. The filter bed as defined in claim 12 wherein said filter aid material is selected from the group consisting of cellulose fibers, polyacrylonitrile fibers, Teflon fibers, nylon fibers, rayon fibers, polypropylene fibers, and poly-vinyl chloride fibers.
14. The filter bed as defined in claim 13 wherein said fibers have an average length of about 10 to about 1000 microns.
15. The filter bed as defined in claim 11 wherein said active particulate material is activated carbon.
16. The filter bed as defined in Claim 11 wherein said filter aid material has been further treated with a second electrolyte-type compound to produce an enhanced surface charge which is the same as said normal surface charge by bonding to said treated filter aid material.
17. A filter bed as defined in Claim 16 wherein said filter aid material normally has a negative charge in aqueous suspension.
18. An improved filter bed comprising: a mixture of treated cellulose fibers and activated carbon particles, said carbon particles having a negative surface charge, and said mixture producing a clumping phenomenon, wherein said cellulose fibers comprise about 5 to 95%, by weight, of said bed, and wherein said cellulose fibers have been treated with an electrolyte-type compound that produces a positive surface charge by bonding to the surface of said cellulose fibers.
19. The filter bed as defined in Claim 18 wherein said electrolyte-type compound is a cationic organic poly-electrolyte.
20. The filter bed as defined in Claim 19, wherein said cellulose fibers comprise about 25% to 60%, by weight, of said bed.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US076,065 | 1979-09-17 | ||
| US06/076,065 US4238334A (en) | 1979-09-17 | 1979-09-17 | Purification of liquids with treated filter aid material and active particulate material |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1142452A true CA1142452A (en) | 1983-03-08 |
Family
ID=22129731
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000354601A Expired CA1142452A (en) | 1979-09-17 | 1980-06-23 | Purification of liquids with treated filter aid material and active particulate material |
Country Status (2)
| Country | Link |
|---|---|
| US (1) | US4238334A (en) |
| CA (1) | CA1142452A (en) |
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| US3242073A (en) * | 1963-03-07 | 1966-03-22 | Dow Chemical Co | Removal of microorganisms from fluids |
| US3352424A (en) * | 1964-02-07 | 1967-11-14 | Dow Chemical Co | Coated filter aids |
| US3250702A (en) * | 1963-03-08 | 1966-05-10 | Union Tank Car Co | Process for purifying liquids and particulate ion exchange material used therefor |
| DE1805779A1 (en) * | 1967-10-30 | 1969-08-21 | Kieselguhr De Mexico S A | Process for the production of diatomaceous earth |
-
1979
- 1979-09-17 US US06/076,065 patent/US4238334A/en not_active Expired - Lifetime
-
1980
- 1980-06-23 CA CA000354601A patent/CA1142452A/en not_active Expired
Also Published As
| Publication number | Publication date |
|---|---|
| US4238334A (en) | 1980-12-09 |
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