WO2007150027A2

WO2007150027A2 - System and method for removing a dissolved substance from a solution

Info

Publication number: WO2007150027A2
Application number: PCT/US2007/071897
Authority: WO
Inventors: Ryszard Jankowiak; Yuri Markushin
Original assignee: Kansas State University Research Foundation
Priority date: 2006-06-23
Filing date: 2007-06-22
Publication date: 2007-12-27
Also published as: WO2007150027A3

Abstract

A system for removing a dissolved substance from a solution comprises a channel (10) defining a flow path of the solution, a first set of electrodes (20) proximate an inner surface of the flow path, and a second set of electrodes (22) proximate an inner surface of the flow path. A solution including a plurality of positive ions and a plurality of negative ions is introduced into the channel (10). A first varying electric field is applied to the channel (10) via the first set of electrodes (20) and a second varying electric field is applied to the channel (10) via the second set of electrodes (22). The first and second fields cause at least one region of concentration of positive ions and at least one region of concentration of negative ions, the first and second regions being located such that at least a portion of the negative ions combine with at least a portion of the positive ions to create a crystal structure.

Description

SYSTEM AND METHOD FOR REMOVING A DISSOLVED SUBSTANCE FROM A

SOLUTION

RELATED APPLICATIONS The present application is a nonprovisional patent application and claims priority benefit, with regard to all common subject matter, of earlier-filed U.S. provisional patent application titled "DESALINATION OF SEAWATER", Serial No.

60/805,713, filed June 23, 2006. The identified earlier-filed application is hereby incorporated by reference in its entirety.

FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

The present invention was developed with support from the U.S. government under ONR grant BG0064, project number GOCH000029. Accordingly, the U.S. government has certain rights in the present invention.

BACKGROUND

1. FIELD

The present technology relates to systems and processes for removing a dissolved substance from a solution. More particularly, embodiments of the technology involve a system and method for desalinating water using electrophoresis to create supersaturated areas in a stream of saltwater to induce salt crystallization.

2. DESCRIPTION OF RELATED ART

The worldwide demand for freshwater increases along with the world's population, making it increasingly challenging to meet freshwater demand for such essential activities as drinking and agriculture. Because the vast majority of the earth's water is found in the oceans, an efficient and large-scale desalination process could help meet the demand for fresh water by deriving freshwater from seawater.

Desalination has conventionally been performed using thermal processes (such as multi-stage flash distillation, multiple effect distillation, and vapor compression) and membrane-based methods. Various aspects of conventional desalination processes render them undesirable in certain situations. For example, conventional desalination processes may create as a byproduct a brine stream solution with highly-concentrated dissolved salt. Such brine streams can be damaging to the environment and therefore must be properly disposed of to avoid harming the environment. Managing the proper disposal of large quantities of brine can substantially add to the overall cost and complexity of the desalination process.

Accordingly, there is a need for an improved desalination process that does not suffer from the limitations of the prior art.

SUMMARY OF THE INVENTION

The present teachings provide an improved system and method for removing a dissolved substance from a solution. Particularly, embodiments of the present technology provide a system for removing a dissolved substance, such as salt, from an aqueous solution, wherein the system comprises a channel defining a flow path of the solution, a first set of electrodes proximate an inner surface of the flow path, and a second set of electrodes proximate an inner surface of the flow path.

A solution including a plurality of positive ions and a plurality of negative ions is introduced into the channel, and a first varying electric field is applied to the channel via the first set of electrodes and a second varying electric field is applied to the channel via the second set of electrodes. The first and second fields create moving electric field gradients that induce at least one region of concentration of positive ions and at least one region of concentration of negative ions, the two regions being located such that at least a portion of the negative ions combine with at least a portion of the positive ions to create a crystal structure. The crystal structure is then removed from the channel.

This Summary is provided to introduce a selection of concepts in a simplified form that are further described below in the Detailed Description. This Summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used to limit the scope of the claimed subject matter.

BRIEF DESCRIPTION OF THE DRAWINGS

Preferred implementations of the present technology are described in detail below with reference to the attached drawing figures, wherein:

FIG. 1 is a perspective fragmentary view of a crystallization channel constructed according to principles of the present teachings;

FIG. 2 is a schematic diagram of an exemplary control system for generating varying electric fields via a plurality of electrodes associated with the crystallization channel of FIG. 1 ;

FIG. 3 is a graph illustrating multiple dynamic equilibrium electric field gradients resulting from the electric fields within the channel of FIG. 1 ;

FIG. 4 is a graph illustrating a crystal structure formed near a region of a zero potential equilibrium point of an electric field gradient, the crystal structure comprising positive and negative ions combined in an area of supersaturation;

FIG.5 is a diagram illustrating a first pattern of electrodes associated with the channel of FIG. 1 ;

FIG. 6 is a diagram illustrating a second pattern of electrodes associated with the channel of FIG. 1 ; and

FIG. 7 is a diagram illustrating a third pattern of electrodes associated with the channel of FIG. 1.

DETAILED DESCRIPTION

A crystallization channel embodying principles of the present teachings is illustrated in Fig. 1 and designated generally by the reference numeral 10. The crystallization channel 10 generally comprises a top wall 12, a bottom wall 14, a first side wall 16, and a second side wall 18 that define a passage through which a solution passes during a process of removing a dissolved substance from the solution. As explained below, the process of removing the dissolved substance involves electronically controlled supersaturation and crystallization of ions that make up the dissolved substance. The solution may be an aquatic solution (i.e., wherein the solvent is water) or comprise an organic-based solvent such as an alcohol, hydrocarbon, or ketone. An exemplary list of water-soluble salts that may be removed from a solution includes, but is not limited to, NaCI; NaNO₃; AgNO₃; CuSO₄; KNO₃; K₂CO₃; all nitrate (NO₃-), nitrite (NO₂-), chlorate (CIO₃-), and perchlorate (CIO₄ ) salts; all alkali metal (Li⁺, Na⁺, K⁺, Rb⁺, Cs⁺) and ammonium (NH₄ ⁺) salts; halogen (Cl , Br, I ) salts; acetate (C₂H₃O² ) salts; sulfate (SO₄ ² ) salts; alkali metal and alkaline earth (Be²⁺, Mg²⁺, Ca²⁺, Sr²⁺, Ba²⁺, Ra²⁺) sulfides; ammonium sulfide; MgCrO₄; alkali metal hydroxides; carbonates, bicarbonates, phosphates, nitrates, sulfates, hydroxides and borates of Na, Li, K, Ca and Mg from aqueous solutions including brines; barium sulfate; rare earth salt crystals including, but not limited to — erbium acetate Er(CH₃COO)₃, samarium sulfate Sm₂(SO₄)₃, praseodymium sulfate Pr₂(SOJ₃, potassium alum KAI(SO₄)₂, and chromium alum KCr(SO₄)₂; ammonium dihydrogen phosphate(ADP- salt); monoammonium phosphate; ammonium magnesium sulfate (AMAG-salt); ammonium nickel magnesium sulfate(AMNI-salt); ammonium sulfate potassium alum; potassium aluminum sulfate 12-hydrate; chromium alum; potassium chromium sulfate 12-hydrate; red prussiate of potash; potassium hexacyanoferrate[lll]; rochelle salt; potassium sodium tartrate 4-hydrate; copper sulfate-5-hydrate; magnesium sulfate 7- hydrate; nickel sulfate; ammonium magnesium cobalt sulfate (AMCO-salt); and carbonate salt (potassium carbonate, potash). By way of example, the present technology may be used to remove one or more solutes from seawater, such as the most prominent ions found in seawater and listed in Table 1. Chemical % by % by

Dissolved Formula weight of weight

Ion and dissolved of

Charge ions seawater

Chloride (CI^") 55.04 1.898

Sodium (Na⁺) 30.61 1.0556

Sulfate (SO₄ ²-) 7.68 0.2649

Magnesium (Mg⁺) 3.69 0.1272

Calcium (Ca²⁺) 1.16 0.04

Potassium (K⁺) 1.1 0.038

Bicarbonate (HCO₃ ) 0.41 0.014

Bromide (Br) 0,19 0,0065

Boric Acid (H₃BO₃) 0.07 0.0026

Strontium (Sr²⁺) 0.04 0.0013

Fluoride (F-) 0,002 0.0001

Total 99.992 3.4482

Table 1 : Dissolved ions in seawater

Turning again to the channel 10 illustrated in Fig. 1 , a first plurality of electrodes 20,22 is associated with the top wall 12 of the channel 10 and a second plurality of electrodes (not shown) is associated with the bottom wall 14 of the channel 10. The second plurality of electrodes may be similar or identical to the electrodes 20,22, therefore only the electrodes 20,22 will be described herein with the understanding that the second plurality of electrodes may present similar characteristics. The electrodes 20,22 may be separated from the inside of the channel 10 by a dielectric material (such as the wall 12 itself or a separate dielectric coating), or may be exposed to the inside of the channel 10. An alternating electric potential is applied to the first and second plurality of electrodes by an electric circuit that is part of a control system, explained below.

The electrodes 20,22 are divided into two sets of electrodes, namely set 20 and set 22. Both sets 20 and 22 include elongated electrodes extending generally transversely to a longitudinal axis of the channel 10. The electrodes of set 20 are joined via a common contact 24 running generally parallel with the longitudinal axis of the channel 10 near a first side of the channel 10, and the electrodes of set 22 are joined via a common contact 26 running generally parallel with the longitudinal axis of the channel 10 near a second side of the channel 10. Thus, all of the electrodes of set 20 are electrically interconnected and may be energized at a first single point, such as a conductive pad (not shown) connected to the common contact 24. Similarly, all of the electrodes of set 22 are electrically interconnected and may be energized at a second single point connected to the common contact 26.

As illustrated in FIG 1 , the first set 20 of electrodes is at least partially interdigitated with the second set 22 of electrodes. In other words, each of the electrodes of set 20 lies generally between two of the electrodes of set 22, and each of the electrodes of set 22 lies generally between two of the electrodes of set 20. Additionally, the electrodes 20,22 may be substantially in line with, or shifted relative to, the electrodes associated with the bottom wall 14 of the channel 10.

While the illustrated channel 10 has been described as being associated with four sets of electrodes (two associated with the top wall 12 and two associated with the bottom wall 14), it will be appreciated that the present teachings contemplate the use of virtually any number of sets of electrodes on each side of the channel 10 such as, for example, four sets of electrodes on the top wall 12 and four sets of electrodes on the bottom wall 14. Furthermore, the electrodes do not need to be associated with the top wall 12 and the bottom wall 14 of the channel 10, as illustrated and described, but may be placed, for example, on side walls of the channel 10 without departing from the ambit of the present teachings.

Similarly, the size and shape of the channel 10 may vary from the size and shape illustrated and described herein. According to an exemplary implementation, the height of the channel 10 (the separation between the top wall 12 and the bottom wall 14) is preferably within the range of about 0.01 mm to about 1.0mm, more preferably within the range of about 0.05mm to about 0.5mm, and most preferably about 0.1 mm. According to the exemplary implementation, the width of the channel 10 (the separation between the first side wall 16 and the second side wall 18) is preferably within the range of about 0.1 mm to about 10mm, more preferably within the range of about 0.5mm to about 5mm, and most preferably about 1.0mm. According to the exemplary implementation, the length of the channel 10 is preferably within the range of about 1cm to about 100cm, more preferably within the range of about 5cm to about 50cm, and most preferably about 10cm.

Virtually any number of electrodes may be used, and the preferred number, shape, and orientation of electrodes may vary from one implementation to another. The total number of electrodes used may be determined, in part, by the size and configuration of the channel 10 and by the complexity of the desired electric field gradients. In this regard, the plurality of electrodes can comprise the two or more sets of electrodes as explained above. By way of example, a total of between 10 and 5,000 or more electrodes may be used . A larger number of electrodes will generally generate better defined or "smoother" electric field gradients with more gradual slopes, while using a smaller number of electrodes will result in less smooth electric field gradients with steeper slopes. Electric field gradients with steeper slopes are generally more efficient in crystallization of dissolved ionic substances, but are not essential to the present technology.

Each of the electrodes may be of any suitable size and geometry. In this regard, each of the first and second sets 20,22 of electrodes may comprise electrodes that differ in size, shape, or both. While the particular dimensions of the electrodes are not critical to the operation of the channel 10, in an exemplary implementation the electrode width is preferably within the range of about 0.01 μm to about 10OOμm, more preferably within the range of about 0.1 μm to about 100μm, even more preferably within the range of about 1 μm to about 10μm, and most preferably about 5μm. Similarly, the separation distance between electrodes is not critical to the operation of the present teachings but may be, for example, be within the range of about 5μm to about 500μm. A larger distance between electrodes will generally require longer electric waveforms and will thus generally result in gradients with more gradual slopes. According to a second exemplary implementation, the width of the channel 10 is about 34mm, the length of the channel 10 is about 12.5cm, the width of the electrodes 20,22 is about 150μm, and the distance between the electrodes 20,22 is about 1.5mm.

The process of separation and crystallization involves electrically energizing the electrodes 20,22 to create varying electric fields in the channel 10, resulting in one or more moving electric field gradients, as explained below in greater detail. The gradients generally move along a length of the channel 10, and result in the crystallization of a substance dissolved in the solution passing through the channel 10, such as salt. An exemplary control system 28 is illustrated in Fig. 2 for controlling operation of the electrodes. The exemplary control system 28 generally comprises an interface 30, a controller 32, a plurality of signal conditioning elements 34,36,38,40, and a plurality of electrode contacts 42,44,46,48. The interface 30 may include a user interface for receiving information or instructions from a user, communicating information to a user, or both. Alternatively or in addition to a user interface, the interface 30 may include a machine interface (wired or wireless) for receiving information or instructions from an external electronic device, communicating information or instructions to an external electronic device, or both. By way of example, the interface 30 may include a keyboard and display or similar user interface and/or an electrical circuit for enabling communications with an external electronic device either directly or via a communications network.

The controller 32 generally directs operation of the control system 28. The controller 32 is preferably a digital integrated circuit and may be a general use, commercial off-the-shelf computer processor. Alternatively, the controller 32 may be a programmable logic device configured for operation with the control system 28, or may be an application specific integrated circuit especially manufactured for use in the control system 28. While illustrated as a single component of the control system 28, the controller 32 may include two or more separate integrated circuits working in cooperation to control operation of the control system 28, and may include one or more analog elements operating in concert with or in addition to the digital circuit or circuits. A memory element (not shown) stores data, instructions, or both used by the controller 32, and may include one or more units separate from the controller 32 or may be internal to the controller 32. The interface 30 and the controller 32 may be substantially similar to, or embodied in, a conventional wave generator.

The signal conditioning elements 34,36,38,40 may include, for example, a digital to analog convertor, a buffer element, or one or more passive electronic components. It will be appreciated by those skilled in the art that in some implementations, the signal conditioning elements 34,36,38,40 may not be needed and therefore may be omitted entirely. The electrode contacts 42,44,46,48 may be conductive pads or similar elements for providing a point of electrical connection between the control system 28 and the electrodes 20,22. Each electrode contact 42,44,46,48 may correspond to a set (20 or 22) of electrodes. The number of signal conditioning elements and/or the number of electrode contacts may correspond to the number of sets of electrodes. Thus, if there are four sets of electrodes each of the electrode contacts illustrated in Fig. 2 may be connected to one of the sets. If there are fewer than four sets (e.g., two sets) of electrodes, only two of the electrode contacts 42,44,46,48 may be used or two of the contacts may be omitted. Similarly, if there are more than four sets (e.g., twenty-four sets) of electrodes, the system 28 may include additional electrode contacts.

In operation, the control system 28 applies a varying voltage potential according to a predetermined waveform to the electrodes via the electrode contacts 42,44,46,48. Such waveforms may include, for example, sawtooth waveforms, triangular waveforms, sinusoidal waveforms, rectangular waveforms, and other continuous waveforms. It may be desirable, for example, to apply sawtooth waveforms to the electrodes, wherein each waveform is similar or substantially identical in frequency, amplitude, and shape to each of the other waveforms, but wherein the phase of each of the waveforms varies according to the set electrodes 20,22. For example, where there are four sets of electrodes and four waveforms, each waveform may be phase shifted at least ninety degrees relative to each of the other waveforms. Furthermore, where sawtooth, triangular, or rectangular waveforms are employed, the wave forms may be curved, or substantially straight. One or more sets of electrodes may be connected to an electrical ground, thus creating a capacitive effect between electrodes driven by a waveform and electrodes connected to electrical ground. In the channel 10 illustrated in Fig. 1 , for example, the first set of electrodes 20 may be connected to an electrical ground while the second set of electrodes 22 may be driven by a waveform, as explained above. Similarly, a first set of electrodes associated with the bottom wall 14 may be connected to electrical ground while the a second set of electrodes associated with the bottom wall 14 may be driven by a waveform. Alternatively, both sets of electrodes 20,22 associated with the top wall 12 of the channel 10 may be driven by a waveform while both sets of electrodes associated with the bottom wall 14 may be connected to electrical ground.

The running electric waves originating from the top and the bottom of the channel propagate through the channel 10 and the solution passing through the channel 10 and create multiple, continuously propagating (moving) electric field gradients along the channel 10, as illustrated in FIG. 3. The gradients tightly focus the ions of interest characterized by the same or similar electrophoretic mobilities. Ions with different mobilities may be focused using different amplitudes of the electric field strength, E_eff, thereby fulfilling the equilibrium gradient condition for each ion:

V_p = μ,(E_eff),

where V_p is the phase velocity of the running gradients, and μ, is the electrophoretic mobility of the ion "i." E_eff may vary from one portion of the channel 10 to another. The phase velocity V_p of the ions moving along the channel 10 may also be expressed as

Vp = fλ

where f is the frequency and λ is the wavelength of the running electric waves. Thus, the frequency of the running electric waves and the corresponding waveforms of electric potential that energize the electrodes 20,22, is related to the electrophoretic mobility of the ions of interest in the solution and will differ from one implementation to another. In an exemplary implementation, the frequency of the electric waves generated by the electrodes 20,22 is preferably within the range of about 0.5Hz to about 100Hz, more preferably within the range of about 1.0Hz to about 80Hz, and most preferably about 2.0Hz. In an exemplary implementation, the amplitude of the electric waves generated by the electrodes 20,22 is preferably within the range of about 0.1V to about 10.0V, more preferably within the range of about 0.5V to about 5.0V, and most preferably about 1.0V.

In Fig.3, the horizontal axis 50 corresponds to spatial displacement along the channel 10, while the vertical axis 52 corresponds to electric field magnitude and polarity. Each of the diagonal lines in the graph of Fig. 3 represents an electric field gradient propagating through the channel 10, and can be pictured as moving in the graph of Fig. 3 from the left to the right at a velocity equal to the phase velocity of the electric wave forms. Thus, the varying electric fields generated by the electrodes combine to create one or more moving electric field gradients, each gradient including a positive electric field portion 54 and a negative electric field portion 56, as well as a zero potential equilibrium 58.

The strength of the electric field is generally greater further from the horizontal axis. For example, the electric field represented by the top of each of the diagonal lines will generally be the positive electric field portion 54 with the greatest strength, and the electric field represented by the bottom of each of the diagonal lines in will generally be the negative electric field portion 56 with the greatest strength.

As the fields propagate through the channel 10, positive ions encountered by the positive electric field portion 54 are urged toward the zero potential equilibrium 58 while negative ions encountered by the negative electric field portion 56 are also urged toward the zero potential equilibrium 58. In the graph illustrated in Fig. 3, this phenomenon can be described as positive ions moving from above the horizontal axis toward the horizontal axis, and negative ions moving from below the horizontal axis towards the horizontal axis.

Thus, the dynamic multiple equilibrium gradient results in a region of concentration of positive ions and a region of concentration of negative ions. The region of concentration of positive ions is sufficiently proximate the region of concentration of negative ions to cause at least a portion of the negative ions to combine with at least a portion of the positive ions to create a crystal structure. The crystal structure is initially small and moves along the channel 10 with the electric field gradient. As the crystal structure grows, however, it will eventually become too large to sustain such movement and will get caught within the channel or in a filter or trap designed to catch and remove the crystals, thus preventing further movement. Stationary crystals continue to grow, however, as regions of supersaturation collide with the crystals. The graph of Fig. 4 illustrates the electric field gradients of Fig. 3 and a crystal structure formed of various ions concentrated by one of the gradients. The crystal structure depicted in the graph of Fig. 4 includes two sizes of ions, large ions representing ions of a first plurality and smaller ions representing ions of a second plurality. These may represent, for example, Na⁺ and Cl^" ions found in saltwater. The positive and negative ions concentrate generally in the vicinity of the zero electric potential equilibrium points. More particularly, a region of concentration of positive ions may be created in the positive electric field portion 54 of the gradient near the zero potential equilibrium 58, and a region of concentration of negative ions may be created in the negative electric field portion 56 of the gradient proximate the zero potential equilibrium 58. When the positive and negative ions are thus concentrated proximate one another, at least a portion of the ions will combine to form a crystal structure.

At any point during the formation of the crystal, the crystal may be removed from the channel 10. This may be accomplished, for example, by using a paper filter or similar filter or trap element to catch the formed crystals, wherein the filter or trap element is removed from the channel and cleansed or discarded.

It should be noted that certain embodiments of the present technology are concerned with the concentration and crystallization of ions, as opposed to the separation of the components of a solution.

As explained above, the electrodes associated with the channel 10 may be subdivided into virtually any number of sets of electrodes. Fig. 5 illustrates an implementation of the present technology that includes four sets of electrodes on the top of the channel 10 and four sets of electrodes on the bottom of the channel 10. In Fig. 5, a first set of electrodes is indicated by the letter A, a second set of electrodes is indicated by the letter B, a third set of electrodes is indicated by the letter C, and a fourth set of electrodes is indicated by the letter D. For simplicity, only the electrodes found on the top wall 12 of the channel 10 are illustrated in Fig. 5. It will be appreciated, however, that an identical array of electrodes including four sets of electrodes may be placed on the bottom wall 14 of the channel 10. If the pattern of electrodes depicted in Fig. 5 were applied to the top wall 12 and to the bottom wall 14 of the channel 10, a total of eight sets of electrodes would be associated with the channel 10.

Alternative implementations of the electrodes are illustrated in Figs.6 and 7, where Fig. 6 illustrates a plurality of electrodes divided into two sets and Fig. 7 illustrates a plurality of electrodes comprising a single set. The electrodes depicted in Fig. 6 are interconnected in a manner similar to the electrodes 20,22 illustrated in Fig. 1. If the pattern of electrodes depicted in Fig . 6 were applied to the top wall 12 and to the bottom wall 14 of the channel 10, a total of four sets of electrodes would be associated with the channel 10. If the pattern of electrodes depicted in Fig. 7 were applied to the top wall 12 and to the bottom wall 14 of the channel 10, a total of two sets of electrodes would be associated with the channel 10. Figures 5-7 depict three exemplary electrode patterns contemplated by the present teachings. Other, equally- preferred patterns of electrodes may be used with virtually any number of electrode sets.

Although the present technology has been described with reference to the preferred embodiments illustrated in the attached drawings, it is noted that equivalents may be employed and substitutions made herein without departing from the scope of the invention as recited in the claims. It will be appreciated, for example, that the channel 10 need not be rectangular, but may be virtually any shape including, for example, cylindrical.

Having thus described preferred implementations of the present technology, what is claimed as new and desired to be protected by Letters Patent includes the following:

Claims

CLAIMS:

1. A method for removing a dissolved substance from a solution, the method comprising: passing the solution through a fluid channel, the solution including a plurality of positive ions and a plurality of negative ions; and applying a first varying electric field and a second varying electric field to at least a portion of the channel, the first and second fields causing at least one region of concentration of positive ions and at least one region of concentration of negative ions, the positive ion region and the negative ion region being located such that at least a portion of the negative ions combine with at least a portion of the positive ions to create a crystal structure.

2. The method as set forth in claim 1 , further comprising applying the first varying electric field and the second varying electric field to the channel by energizing a first plurality of electrodes proximate the channel according to a first waveform and energizing a second plurality of electrodes proximate the channel according to a second waveform.

3. The method as set forth in claim 2, the first waveform and the second waveform having similar shapes, amplitudes, and frequencies, and the first waveform being phase shifted relative to the second waveform.

4. The method as set forth in claim 3, the first and second waveforms each being chosen from the group consisting of a sawtooth waveform, a sinusoidal waveform, a triangular waveform, and a rectangular waveform.

5. The method as set forth in claim 1 , the first and second varying electric fields cooperating to create a moving electric field gradient with positive and negative electric field portions and a zero electric potential equilibrium point, wherein positive ions are urged toward the zero potential equilibrium point by the positive electric field portion and negative ions are urged toward the zero potential equilibrium point by the negative electric field portion.

6. The method as set forth in claim 5, the positive electric field portion of the electric gradient being stronger further from the equilibrium point and the negative electric field portion of the electric gradient being stronger further from the equilibrium point.

7. The method as set forth in claim 1 , further comprising applying a third varying electric field and a fourth varying electric field to at least a portion of the channel, the first, second, third, and fourth fields causing the at least one region of concentration of positive ions and the at least one region of concentration of negative ions.

8. The method as set forth in claim 7, further comprising applying the third varying electric field and the fourth varying electric field into the channel by energizing a third plurality of electrodes proximate the channel according to a third waveform and energizing a fourth plurality of electrodes proximate the channel according to a fourth waveform.

9. The method as set forth in claim 8, the first, second, third, and fourth waveforms having similar shapes, amplitudes, and frequencies, and the first waveform being phase shifted relative to the second waveform.

10. The method as set forth in claim 1 , further comprising the step of removing the crystal structure from the channel.

11. The method as set forth in claim 1 , the channel having a height within the range of about 0.01 mm to about 1.0mm, a width within the range of about 0.1 mm to about 10mm, a length within the range of about 1.0cm to about 100cm.

12. The method as set forth in claim 1 , the channel having a height within the range of about 0.05mm to about 0.5mm, a width within the range of about 0.5mm to about 5mm, a length within the range of about 5cm to about 50cm.

13. The method as set forth in claim 1 , the channel having a height of about 0.1 mm, a width of about 1.0mm, and a length of about 10cm.

14. A method for removing a dissolved substance from a solution, the method comprising: passing the solution through a fluid channel, the solution including a plurality of positive ions and a plurality of negative ions; and applying a first varying electric potential to a first set of electrodes, the first set of electrodes being on a top of the channel; applying a second varying electric potential to a second set of electrodes, the second set of electrodes being on the top of the channel and interdigitated with the first set of electrodes; applying a third varying electric potential to a third set of electrodes, the third set of electrodes being on a bottom of the channel; and applying a fourth varying electric potential to a fourth set of electrodes, the fourth set of electrodes being on the bottom of the channel and interdigitated with the third set of electrodes, the first, second, third, and fourth varying electric potentials resulting in a moving electric field gradient that causes at least one region of concentration of positive ions and at least one region of concentration of negative ions, the positive ion region and the negative ion region being located such that at least a portion of the negative ions combine with at least a portion of the positive ions to create a crystal structure.

15. The method as set forth in claim 14, each of the varying electric potentials oscillating according to a running waveform, wherein each of the waveforms presents a phase difference of at least ninety degrees relative to the other waveforms.

16. The method as set forth in claim 15, wherein each of the waveforms is a sawtooth waveform.

17. The method as set forth in claim 15, each of the waveforms presenting an amplitude within the range of about 0.1V to about 10V and a frequency within the range of about 0.5Hz to about 100Hz.

18. A system for removing a dissolved substance from a solution, the system comprising: a channel defining a flow path of the solution; a first set of electrodes proximate an inner surface of the flow path; a second set of electrodes proximate an inner surface of the flow path; and an electric circuit for applying a first electric potential according to a first waveform to the first set of electrodes and a second electric potential according to a second waveform to the second set of electrodes, the first and second electric waveforms presenting amplitudes within the range of about 0.5V to about 1.5V.

19. The system as set forth in claim 18, each of the first set of electrodes and each of the second set of electrodes being substantially elongated and extending generally perpendicular to a longitudinal axis of the channel.

20. The system as set forth in claim 18, the first set of electrodes and the second set of electrodes located on a single surface, the first set electrodes being interdigitated with the second set of electrodes.

21. The system as set forth in claim 18, further comprising an interface for receiving information relating to the waveforms, the electrical circuit applying the waveforms according to the information.

22. The system as set forth in claim 18, the channel having a height within the range of about 0.01 mm to about 1.0mm, a width within the range of about 0.1 mm to about 10mm, a length within the range of about 1.0cm to about 100cm.

23. The system as set forth in claim 18, the channel having a height within the range of about 0.05mm to about 0.5mm, a width within the range of about 0.5mm to about 5mm, a length within the range of about 5cm to about 50cm.

24. The system as set forth in claim 18, the channel having a height of about 0.1 mm, a width of about 1.0mm, and a length of about 10cm.