BIPOLAR ELECTROCHEMICAL SPACER

Abstract

The present invention provides a device capable of reducing resistance and increasing the rate of ion exchange in an electrodialysis, electrodeionization, or capacitive deionization apparatus, and a method for producing the device. More specifically, the device is an electrodialysis spacer designed to have an ionically conductive surface of cationic, anionic, or a combination of both nature, which acts as a conductive pathway for ions as they move toward their respective electrodes. The method for producing the spacer involves coating a substrate, such as a woven mesh, expanded net, extruded net, or nonwoven material, with solutions of a permanent selective ionomer and applying that substrate to an inert spacer material that has been subjected to chemical or mechanical etching.

Description

BIPOLAR ELECTROCHEMICAL SPACER Field of Invention The present invention relates to a bipolar ion-conducting spacer and to a method for producing an ion-conducting spacer for use in an ion exchange water treatment system, such as electrodialysis (ED), electrodialysis reversal (IED), electrodialysis metathesis (MED), reverse electrodialysis (EDI), or electrodeionization (EDI). Background of the Invention In the current state of the art, electrodialysis, as a method, is used to selectively remove positive and negative ions from a water source, such as brackish water or the brine solution produced in reverse osmosis units, by transporting salt ions from one solution to another across ion-exchange membranes after the application of an electric current. The electrodialysis apparatus itself consists of a pair of electrodes, where a voltage is applied to initiate an electrochemical reaction, alternating between anion and cation exchange membranes, which are used to selectively separate ions from one stream while concentrating ions in adjacent streams of a dilute solution feed stream (dialysate compartment). Ref. 309372 for concentrating the flow (brine compartment) and spacer materials, which are placed between the ion exchange membranes. While the anode attracts negatively charged ions (e.g., chloride) and the cathode attracts positively charged ions (e.g., sodium), the main function of the spacer material is to create turbulence in the flow field and restrict contact between the membranes. Although the spacer provides a necessary function for the electrodialysis unit, this comes at a cost. The electrical energy required to transport ions from one stream to another is a function of the system's resistance, according to Ohm's law (Eq. 1), where V is the electrical potential, i is the current density, and A is the resistance. While the desalination rate can be accelerated by increasing the electrical potential (V), the current density (i) (i.e., the amount of electrical current flowing per unit cross-sectional area of ​​a material), as a function of the electrical potential (V), this can only be increased up to a point of electrochemical polarization impedance.Returning to the second, more highly mutable function, the system resistance, this opposing force can be greatly affected by K, the conductivity of water in the unit (which consequently decreases as ions are removed and the distance between the membranes decreases), and L, determined by the thickness of the spacer. Therefore, the resistance scales linearly (i.e., increases) with the intermembrane space, as seen in equation 2. V=i*R Equation 1 R = K'1* L Equation 2 Previous attempts to improve the design of the constructed spacer to overcome the weaknesses mentioned above primarily use inert polymeric materials that can create turbulence, resulting in a higher proportion of ion contact with the membrane surfaces and subsequent increased ion exchange rates, but they do not provide any means of reducing electrical resistance. As evidenced in Herron et al. (U.S. Patent No. 5,407,553), the inventors describe an electrocell having a novel design to promote high turbulence in that portion of electrocells sensitive to fouling or current-limiting problems and membranes (e.g., anodic membrane, brine membranes, and cathode membranes) that are intentionally allowed to be diverted in response to fluid pressure differentials so that a flow path with a constantly changing direction is formed.However, the turbulence nzcann / nznz / E / YiAi created by the invention detailed in patent '553 has serious limitations that (1) require an energy input that reduces the overall efficiency of the process and (2) create the rate-limiting step of the physical manipulation of saline water through a dialysis stack. Furthermore, U.S. Patent No. 6,090,258, granted to Mirsky et al., describes an ion-exchange spacer and processes for manufacturing the spacer that incorporates both heterogeneous and homogeneous ion-conducting coatings. In particular, the authors describe a process for coating a polymer network with a polymer coating, where the coating contains ion-exchange resin particles to impart ion-exchange capacity. Although it reduces resistance, the described method is limited because it can only produce a unipolar conducting spacer, consisting of either cation-conducting or anion-conducting spacer material. This greatly diminishes its usefulness in water desalination as a unit that can remove both positively and negatively charged ions using a bipolar spacer substrate. There are other previous attempts using textured membranes for enhanced ion exchange. Several descriptions impart a three-dimensional shape to the membrane surface while also varying the membrane thickness (see, in general, patent applications No. WO2005009596A1, WO2002014224A1, and US20170029586A1). Therefore, although this reduces resistance, it is limited because it does not create sufficient turbulence in the fluid flow field nor provide a sufficient decrease in the amount of electrical resistance required to advance ion conduction, and electrodialysis is beyond current practice. Therefore, there is a prevalent need in the art for an apparatus and method to create a bipolar conductive spacer that minimizes electrical resistance through an anionic and cationic coating and creates sufficient turbulence to improve and advance electrodialysis, electrodeionization, and capacitive deionization beyond their current limited state. The present invention satisfies this prevalent need in the art and seeks to remedy all the deficiencies detailed above. Summary of the Invention The electrodialysis device described herein illustrates an apparatus and method for its use, which features a mixture of anionic and cationic ion-exchange materials bonded to an electrodialysis spacer surface material (which may be porous fabric or non-woven) to produce a network of anionic and cationic exchange channels resulting in an ionically conductive, bipolar electrochemical spacer device designed to (1) increase the surface area of ​​the substrate (applied network or mesh material) and (2) create an anionic and cationic substrate by applying solutions to the surface of the spacer material. This increase in surface area directly enhances the creation of turbulent passages, thereby improving ion exchange rates through amplified contact velocities with appropriate membranes.Similarly, the creation of a bipolar ion-conducting spacer surface with a dual charge allows for a much faster ion exchange rate than that of a unipolar ion-conducting surface. Brief Description of the Figures With reference now to figures in which the represented elements are not necessarily shown to scale, or similar, the elements may be designated with the same reference numbers across the various figures. In the figures: Figure 1 is a detailed schematic representation of an operational electrodialysis apparatus described herein for reducing the resistivity of the dilute and concentrate chambers. nzcann / nznz / E / YiAi Figure 2 is a general arrangement of an exploded view of the spacers between alternating membrane types within an electrodialysis apparatus. Figure 3 is a detailed schematic of a conductive bipolar spacer surface prepared by a process with anionomer and cationomer solutions applied simultaneously to an outer surface of an ion exchange unit spacer along with the movement of anions and cations along the spacer surface en route to the surface of the ion exchange membranes. Figure 4 is a representation of the present invention having an ionic surface that is the same as the surface of the adjacent membrane. Figure 5 is a flow diagram detailing the process of applying ionomer to the surface of a spacer material that first modifies the spacer surface. Figure 6 is a flow diagram detailing the process of applying ionomer to the surface of a spacer material without surface preparation or modification. Figure 7 is a simplified schematic of the process of applying ionomer to the outer surface of a spacer to increase the conductivity of the spacer material. Figure 8 is a simplified schematic of a continuous roll-to-roll process for producing bipolar conductive spacer material. Figure 9 is a graph comparing the resistance of an electrodialysis spacer with and without conductive spacers Figure 10 is a graph comparing the resistance of an electrodialysis spacer with and without conductive spacers However, it should be understood that the specific embodiments shown in the figures and the detailed description do not limit the scope of the description. On the contrary, they provide a basis for a person skilled in the art to discern the alternative, equivalent, and modified forms covered by the appended claims. Detailed Description of the Invention TERMINOLOGY The terms used herein will be recognizable to those skilled in the art. Therefore, it should be understood that when not explicitly defined, terms should be interpreted as having the meaning currently accepted by those skilled in the art. In this application, the use of the singular includes the plural, so that the articles *un* and *una* mean at least one, and the use of the conjunction *o* has the inclusive meaning unless specifically stated otherwise. Unless otherwise specified, the term *encompassing* (as well as its other forms, such as *include* and *included*) is open-ended and not intended to be limited to any specifically identified item. Unless otherwise stated, terms such as *element* or *component* encompass not only single modules but also sets or submodules of multiple modules that provide the same features. As used herein, the terms *comprising*, *having*, and *including* are synonymous unless the context indicates otherwise. The advantages of the present invention will be readily apparent to those skilled in the art from the following detailed description, which describes certain preferred embodiments of the invention and provides illustrative examples. Although the following detailed description contains many specific details for illustrative purposes, a person skilled in the art will appreciate that many variations and alterations of the following details are within the scope of the invention. Accordingly, the following embodiments of the invention are set forth without any loss of generality and without imposing any limitations on the claimed invention. nzcann / nznz / E / YiAi While the modalities are described in relation to the description herein, there is no intention to limit the scope to the modalities described here. Rather, the intention is to cover all alternatives, modifications, and equivalents. The present invention provides a device capable of reducing resistance in an electrodialysis, electrodeionization, or capacitive deionization apparatus and a method for producing the device. More specifically, the device is an electrodialysis spacer used to greatly improve ion exchange rates. It is designed to have an ionically conductive surface, either cationic, anionic, or a combination of both, which acts as a conductive pathway for ions as they move toward their respective electrodes: negatively charged ions (e.g., chloride) toward the positively charged anode and positively charged species (e.g., sodium) toward the negatively charged cathode. Furthermore, the invention relates to an electrodialysis, electrodeionization, or capacitive deionization apparatus that uses a spacer material having an ionically conductive surface. The invention also relates to the process and method for producing an ionically conductive and ionically charged spacer, wherein the neutrally charged spacer features a woven mesh or ion-conducting network material. The process involves coating a substrate, such as a woven mesh, expanded network, extruded network, or nonwoven material, with permanent selective ionomer solutions (ionomer solutions being the solubilized form of an ion-exchange resin or membrane). The ionomer solution is applied to the non-conductive spacer via a coating process, such as, for example, spray coating, inkjet printing, curtain coating, or dip coating. The coated spacer is then cured to bond the ion-conducting material to the non-conductive substrate and to remove any supporting surfactants from the spacer surface.Before coating the substrate surface, an additional step can be taken to increase the substrate surface area through chemical or mechanical processes including, but not limited to, acid etching, sandblasting, laser etching to achieve an improved turbulent effect. In a preferred embodiment, the conductive spacer is a coated mesh or an extruded net 110 and 111 used to separate the membranes 105, 106, and 107 in an electrodialysis device as shown in Figure 1. An electrodialysis apparatus comprises an anode 103 and a cathode 104 spanning a series of fluid channels 101, 112, 113, and 102. The fluid channels are separated by ion-exchange membranes 105, 106, and 107. The ion-exchange membranes alternate between anion-exchange membranes 105 and 107 and a cation-exchange membrane 106. The anion-exchange membranes preferably permit the passage of negatively charged ions 108 and substantially block the passage of positively charged ions 109. Cation exchange membranes preferentially allow the passage of positively charged ions 109 and substantially block the passage of negatively charged ions 108.Fluid channels 101 and 102 contain the electrolyte that is in direct contact with the anode 103 and cathode 104, which may be the same fluid or a different one than the fluid entering the electrodialysis apparatus 100. In an electrodialysis cell, when an electrical charge is applied to the anode 103 and the cathode 104, ions in the fluid stream 100 flow through channels 110 and 111 and migrate toward the oppositely charged electrode. The alternating arrangement of the ion-exchange membranes thus produces alternating channels of decreasing ion concentration 112 and increasing ion concentration 113. The number of channels 112 and 113 can be increased by adding more alternating pairs of membranes to increase the capacity of the electrodialysis apparatus. Furthermore, the operating capacity of an individual electrodialysis cell can be significantly increased by configuring the electrodialysis cells into electrodialysis stacks (i.e., a series of multiple electrodialysis cells). To create fluid channels 112 and 113, spacers are inserted between the membranes. This spacer can be composed of two parts as shown in Figure 2. The first part is a spacer frame 210 and 211 that can be made of a plastic or elastomeric material and acts as a seal between the fluid chambers, as well as providing a seal between the internal and external fluids. The second part is a sword mesh 205 and 207, which can be a woven or extruded mesh 205 and 207 that spans the inner opening in the sealing frame 210 and 211 and provides fluid channels between the membranes 203 and 206, and 206 and 209. The sword mesh 205 and 207 and the spacer frame 210 and 211 can optionally be connected to form the spacer 204 and 208, through methods including, by way of example, sonic welding, lamination, or adhesives.By alternating the orientation of spacer 204 and 208, two distinct channels 201 and 202 are formed internally between the anion exchange membrane 203 and 209 and the cation exchange membrane 206. A primary source of electrical resistance in the electrodialysis apparatus is due to the fluid in channel 112 (see Figure 1), as it reduces the ion concentration. The present invention addresses this problem by applying ionomers to the surface of the mesh spacer separating the membranes. In one exemplary embodiment, the ionomers are applied simultaneously, resulting in a surface with bipolar ionic conductivity, exhibiting both cationic and anionic qualities, as shown in Figure 3. Concurrent coating of the mesh substrate 301 produces a surface partially coated with the anion-exchange ionomer 302 and partially coated with the cation-exchange ionomer 303 (see Figure 3). The result is a network of oppositely charged ionic pathways, which can be less resistant to ion flow than the surrounding fluid.Functionally, as depicted in Figure 3, as the ionic solution passes through the electric field in the electrodialysis apparatus, transport is facilitated by ionic pathways to the surface of the adjacent ion-exchange membranes 308 and 309. The anionic coated surfaces 302 have positively charged functional groups 306 that transport negative anions 305 to the anionic membrane 308. Positive cations 304 are repelled by the positively charged functional groups 306 on the anionic coated surface 302. Conversely, the cationic coated surface 303 contains negatively charged functional groups 307 that attract and transport positive cations 304 to the cation-exchange membrane 309, and negative anions 305 are repelled by negative functional groups 307. In another exemplary embodiment, a mesh spacer 401 is coated with a cation-exchange ionomer 407 on one side and an anion-exchange ionomer 408 on the other side, as shown in Figure 4. This coating method extends the ion-exchange material in the flowways away from the surface of the ion-exchange membranes, thereby decreasing the resistance of the flow channels. Here, the cation-exchange membrane 404 extends over the cationic-coated surface 402, and the anion-exchange membrane 406 extends over the anion-exchange surface 403. Figure 5 provides a flow diagram illustrating the production process of the ion-conducting spacer that is the present invention. The first step is surface preparation. Here, a chosen material, such as nylon, PET, PTFE, or any other plastic, is shaped to allow the fluid (e.g., water) to flow around and through it. This process could also include cutting the spacer to the desired size for incorporation into an electrochemical apparatus (e.g., an electrodialysis unit). This sizing step can also be performed at a different point in the process, such as just before incorporation into a device. nzcann / nznz / E / YiAi The second step in the process is surface modification. In this step, the spacer material is modified to allow for greater adhesion between the inert plastic substrate and the ionic coating. The general idea is to increase the substrate's surface energy, which can be achieved through physical and chemical methods. Physical methods include, but are not limited to, flame oxidation, corona discharge plasma, laser etching, hollow cathode glow discharge, and sandblasting. Chemical processes for increasing surface energy include, but are not limited to, treatment with strong acids (chromic, nitric, etc.), peroxide etching, and etching with strong bases (e.g., sodium hydroxide, potassium hydroxide, etc.). After surface modification, the surface is cleaned. The cleaning process involves rinsing the surface alternately with light alcohols (ethanol, 2-propanol, etc.) and deionized water. The clean surface is then dried and ready for the application of the ionic material. The application process is a coating process and can therefore be carried out through methods such as dip coating, spray coating, roller coating, etc. In a preferred embodiment, spray coating is used. Here, a dilute solution containing solubilized nzcann / nznz / E / YiAi ionomer is carried in an air stream. The combined stream passes through an atomizing nozzle and is applied to the spacer surface. The nozzle, the spacer, or both are moved so that the entire exposed surface of the spacer is coated with the solution. Process variables (i.e., solution concentration, number of passes, flow rate, droplet size, etc.) will impact the loading of the spacer material produced. The drying process serves to remove excess solvent and to cure (set) the ionomer in a resin. The drying process can be performed simultaneously with and / or after the coating process. The drying process can be done with or without the addition of a heat source. Heat can be transferred to the spacer by convection, radiation, or conduction, with convection being the preferred method. The next step in the process is to immerse the coated spacer in salt water (for example, a mixture containing a combination of sodium chloride and water). This immersion step allows the ionomer to exchange its pending charge group (such as hydroxide) for a salt ion, such as chloride. The final step in the process is to incorporate the ion-conducting spacer into the electrochemical device (for example, an electrochemical ion separation device). The spacer must be sized to fit within the active area of ​​the device, and preferably outside the sealing area. The spacer can be sized before the coating, after the coating, or at another step in the process. Depending on the orientation of the ion coating, it may be important which side needs to face which membrane. In a preferred embodiment, a spacer with different ion coatings on each side of the spacer is placed so that the anionomer-coated surface faces the anion exchange membrane, and the cationomer-coated surface faces the cation exchange membrane within the stack, as in Figure 4. A conductive spacer can also be produced through a process without surface preparation or modification. The description of the final four steps in Figure 5 details how the process would work. Another preferred embodiment incorporates a spray coating process for applying ionic material. Spray atomizing nozzles 701 and 702 distribute the ionomer solution where pressurized air carries the solubilized ionic material onto a receiving surface. The nozzle tip atomizes the fluid into microdroplets, 703 and 704, which are deposited onto the surface of the spacer 705. In some embodiments, the microdroplets 703 and 704 contain the same ionomer solution, either cationic or anionic, and in other embodiments, the microdroplets 703 contain an anionic ionomer solution, while the microdroplets 704 contain a cationic ionomer solution. Articles 706 (air) and 707 (fan) illustrate the convection drying process in which a fan 707 moves air 706 over the surface of the spacer.The fan 707 can also contain a heating element so that the air 706 transfers heat to aid in the drying process. nzcann / nznz / E / YiAi In yet another embodiment, the bulk spacer material is wound onto a dispensing roll 801, which is fed via rollers to an area where it is exposed on each side to spray ionomeric solution distribution nozzles 802 and 803. The ionomeric solution distribution nozzles 802 and 803 may contain the same ionomeric solution (either anionic or cationic), or the distribution nozzle 802 may dispense either the cationic or anionic ionomeric solution, and the ionomeric solution distribution nozzle 803 may dispense either the cationic or anionic ionomeric solution. Alternatively, the process defined herein may consist of any combination—in parallel, in series, or in alternating combination—that results in the uniform, patterned, regular, or irregular application of the ionomeric solution.Fans 804 and 805 may or may not contain heating elements to provide convective heat transfer for drying the spacer material. Convection accelerates the drying process and helps reduce the amount of material blocking open areas of the spacer. Receiving roll 806 displays the finished material, which can then undergo further processing. Examples Example 1. The nylon mesh spacer was cut to the desired dimension for use in a fluid electrodialysis apparatus. Solutions of solubilized Nafion and an anionic ionomer (FUMION FLA from Fumatech GmbH) were diluted to 1 wt% using reactive alcohol (a mixture of ethanol, methanol, and 2-propanol). The separate solutions were loaded into separate air-driven spray guns. The spacer was held so that one side was exposed to the spray gun. First, the exposed side was sprayed with the Nafion solution, covering all available surfaces. The wet spacer was then dried with a heat gun (a heating coil with a fan and a nozzle to direct the heat). This process was repeated until the desired load of 1.25 mg / in² (0.19 mg / cm²) was applied to the first side. The coated spacer is inverted, exposing the uncoated side to the spray gun.Then, the entire process was repeated with the anionic solution. Six of these spacers were incorporated into a fluid electrodialysis apparatus. The coated spacers were placed between alternating anion and cation exchange membranes. Care was taken to position the anion-coated side of the spacer facing the anion exchange membrane and the cationic-coated side facing the cation exchange membrane. Brackish water was desalinated using this device, and the performance was compared to a standard design where the only difference was that the spacers were not coated with the ionomer solutions. As shown in Figure 9, the resistance of the system with the conductive spacers is lower than that of the baseline cell device with non-conductive spacers at all salinities, and this difference becomes greater as the total resistivity of the system increases (i.e., at low salinity values).In the experiment, the salinity was reduced by two orders of magnitude from the initial concentration. Example 2. The 1 wt% anionic and cationic ionomer solutions were made in the manner described in Example 1. Instead of spraying each solution onto one side of the spacer, the two solutions are sprayed simultaneously onto the nylon spacer. The two solutions are sprayed and the wetted spacers are dried, as described above, until the desired charge of 1.25 mg / in² (0.19 mg / cm²) is reached. The spacer is then inverted, and the process is repeated until the inverted spacer also achieves the desired charge. Spacers made in this manner can be placed between the alternating ion-exchange membranes of the electrodialysis apparatus in any orientation without affecting performance. Six of these spacers were incorporated into an electrodialysis unit, placed between alternating ion-exchange membranes. Brackish water was desalinated using this device, and the performance was compared to a standard design where the only difference was that the spacers were not coated with the ionomer solutions. As shown in Figure 10, the resistance of the experimental design is similar to the control design (identical electrodialysis unit with non-conducting spacers) at the initial concentration. As salt is removed from the product water during the electrodialysis process, the experimental design becomes less resistant relative to the control, and this difference increases as more salt is removed from the system. In the experiment, the salinity was reduced by 1.5 orders of magnitude from the initial concentration. It is hereby stated that, as of this date, the best method known to the applicant for putting the aforementioned invention into practice is the one that is clear from the present description of the invention.

Claims

Having described the invention as above, the following claims are claimed as property:

1. An electrochemical apparatus for reducing resistance in an electrodialysis, electrodeionization, or capacitive device, characterized in that it comprises: a pair of electrodes; an applied voltage; alternating anionic and cationic exchange membranes placed between two of the electrodes for ion separation from a depleted (diluted) stream to a concentrated (brine) stream; an ionically neutral, non-conductive spacer, which may be woven, porous, or non-woven; the spacer having an outer surface expressing an ionically conductive coating adhered to the outer surface of the spacer, wherein the ionically conductive coating is permselective and of a cationic nature, an anionic nature, or both.

2. The electrochemical apparatus according to claim 1, characterized in that the ionically conductive permselective coating is a topical application nzcann / nznz / E / YiAi on the outer surface of the non-conductive neutral ionic spacer which is a woven mesh, an expanded network, an extruded network or a non-woven material.

3. The electrochemical apparatus according to claim 1, characterized in that the permselective, ionically conductive coating is applied to the spacer by a coating process such as, but not limited to, spray coating, inkjet printing, curtain coating, or dip coating.

4. The electrochemical apparatus according to claim 3, characterized in that the coated spacer is cured to ensure the adhesion of the ionically charged, ion-conducting material to the spacer.

5. The electrochemical apparatus according to claim 1, characterized in that the ionically conductive surface forms a network of anionic, cationic, or anionic and cationic exchange channels, which act as a set of conductive pathways for ions and ion exchange.

6. The electrochemical apparatus according to claim 1, characterized in that the spacer surface is chemically altered by acid etching with strong acids (chromic, nitric, etc.), peroxide etching, and chemical etching with strong bases (for example, sodium hydroxide, potassium hydroxide, etc.) to create deformations on the spacer surface, thereby generating turbulent rheological disturbances to achieve an improved ion exchange rate.

7. The electrochemical apparatus according to claim 1, characterized in that the surface of the spacer is mechanically altered by flame oxidation, corona discharge plasma, laser etching, hollow cathode glow discharge or sandblasting to create turbulent rheological disturbances to obtain an improved ion exchange rate.

8. An electrochemical apparatus characterized in that it comprises: a spacer or a plurality of spacers for reducing resistance in an electrodialysis, electrodeionization, or capacitive device, wherein the non-reactive spacer is coated with a conductive, ionically charged coating residing between ion-exchange membranes, exhibiting a surface that is unipolar or bipolar, through a partial or complete coating, thereby facilitating the transport of an ionic solution through ionic pathways oppositely charged to the surface of the adjacent ion-exchange membrane (i.e.,when the anionic coated surfaces have positively charged functional groups that transport negative anions to the anionic membrane and positive cations are repelled by the positively charged functional groups on the anionic coated surface and the cationic coated surface contains negatively charged functional groups that attract and transport positive cations to the cation exchange membrane and negative anions are repelled by negative functional groups) at least one anode or a plurality of anodes; at least one cathode or a plurality of cathodes; one or a plurality of fluid channels separated by one or more alternating anionic and cationic ion exchange membranes,where anion exchange membranes preferentially permit the passage of negatively charged ions and substantially block the passage of positively charged ions, and cation exchange membranes preferentially permit the passage of positively charged ions and substantially block the passage of negatively charged ions, and exhibit alternating pathways of ever-decreasing and ever-increasing ion concentration currents; fluid channels containing electrolytes that are in direct contact with the anode and cathode, which may be the same fluid or a different one than the fluid entering the electrodialysis device; an electrical charge applied to the anode and cathode, causing the ions in the fluid stream to flow through the fluid channels and migrate towards the electrodes that exhibit the opposite electrical charge.

9. The electrochemical apparatus according to claim 8, characterized in that the spacer is coated with a cation exchange ionomer on one side and an anion exchange ionomer on the other side, wherein the oppositely polarized coating extends the ion exchange material in the flow pathways away from the surface of the ion exchange membranes, thereby decreasing the resistance within the flow channels.

10. The electrochemical apparatus according to claim 8, characterized in that the spacers inserted between ionically charged membranes consist of (1) a spacer frame acting as a seal between the fluid chambers and as a seal between the internal and external fluids and (2) a spacer mesh, which may be a woven or extruded mesh, spanning the internal opening in the sealing frame and providing fluid channels between ionically charged membranes through alternating fluid pathways (channels) through the spacer and in contact with the alternating ionically charged membranes.

11. The electrochemical apparatus according to claim 9, characterized in that the spacer is made of a non-reactive, non-ionic plastic or elastomeric material that is made to exhibit ionomers resulting in a spacer that is either unipolar (e.g., positively charged or negatively charged) or bipolar in nature (e.g., exhibiting both positive and negative charges).

12. The electrochemical apparatus according to claim 8, characterized in that the quantity of fluid channels, ion exchange membranes, anodes, cathodes and / or spacers can be increased by adding more alternating pairs of membranes and spacers, thereby increasing the capacity of the electrodialysis device.

13. A method for coating a spacer to produce a unipolar or bipolar conductive ionic spacer, characterized in that it comprises the steps of: preparing the spacer surface, including cutting the spacer to the desired shape to obtain fluid movement through and around the spacer and designing, naming, and inserting appropriately shaped fluid channels to obtain fluid movement through the ion-exchange membranes; modifying the spacer surface to allow increased adhesion between the inert plastic substrate and the ionic coating and to promote turbulence achieved chemically, mechanically, or both; cleaning the spacer surface using alternating light alcohols and deionized water; and applying the ionomeric coating, wherein a solution containing solubilized ionomeric solution is applied to the spacer surface.Drying the spacer to remove excess solvent and to cure and fix the ionomeric solution as a resin, which is carried out simultaneously with or subsequent to the coating process by air drying or fan drying, with or without a heat source; immersing the spacer in a solution containing salt (e.g., sodium chloride and water) so that the ionomer exchanges its pending charge group (such as hydroxide) for a salt ion such as chloride; and fitting the spacer into the electrochemical device so that the conductive coating fits within the active area of ​​the device.

14. The method according to claim 13, characterized in that the application of ionomeric coating on the surface of the spacer can be partial, intermittent, directed, degraded, uniform and / or non-uniform as dictated by the directed ion exchange rate, direction, flow and / or desired path.

15. The method according to claim 13, characterized in that the ionomer coating application process can be achieved by a technique in which the ionomer solution is carried in an air stream and applied through an atomizing nozzle and applied to the spacer surface, in series, in parallel, straddling, or alternating, in such a way as to provide optimal placement and adhesion of the solution on the spacer surface, and the application process continues until the desired coating thickness is achieved.

16. The method according to claim 13, characterized in that the coating process can be carried out by dip coating, spray coating, roller coating and the like.

17. The method according to claim 13, characterized in that a coating is applied by spraying using an atomizing spray nozzle that moves relative to the spacer, the spacer moves relative to the nozzle, or both the nozzle and the spacer move in such a way as to ensure complete or incomplete exposure of the spacer surface and desired concentration and thickness of the solution, wherein the number of passes, flow rate, and droplet size are optimized to ensure adequate coverage of the spacer, whether uniform or non-uniform, with a solubilized ionomeric solution.

18. The method according to claim 13, characterized in that the surface of the spacer is first prepared and then modified to allow greater adhesion between the inert plastic substrate and the ionic coating.

19. The method according to claim 13, characterized in that the spacer can be dimensioned before coating, after coating, or at an intermediate stage in the spacer production process.

20. The method according to claim 13, characterized in that a spacer, having alternate ionically charged coatings on each side of the spacer, is oriented such that the anionomeric coated surface faces a like-charged anion exchange membrane and the catiomeric coated surface faces a like-charged cation exchange membrane.

21. The method according to claim 13, characterized in that the surface preparation and surface modification steps are omitted.

22. A method according to claim 13, characterized in that the process of applying nzcann / nznz / E / YiAi ionomeric solution spray coating to coat a spacer to produce a unipolar or bipolar ionically conductive spacer is achieved by implementing a container (spray gun) and a spray nozzle, or a plurality of containers and spray nozzles, for pressurizing and atomizing microdroplets of solution to deposit on the outer surface of a spacer.

23. The application process according to claim 19, characterized in that the ionomeric solution is a cationic ionomer solution or an anionic ionomer solution and the ionomeric solution of a pressurized container containing a cationic solution is oriented in such a way as to allow cross-coating on the same side (with a combination of positively and negatively charged solutions) of one side of the outer surface of the spacer in a largely overlapping adhesion.

24. The application process according to claim 19, characterized in that a container and a spray nozzle, or a plurality of containers and spray nozzles, for pressurizing and atomizing microdroplets of solution for depositing on the outer surface of a spacer contain similar polarized ionomeric solutions that are grouped, either all positively charged or all negatively charged, for application to one side of a spacer material, which is the result of transport between two opposing rotating rollers to facilitate adhesion of the solution in a roll-to-roll process.

25. The application process according to claim 19, characterized in that a container and a spray nozzle, or a plurality of containers and spray nozzles, for pressurizing and atomizing microdroplets of solution for depositing on the outer surface of a spacer contain different polarized ionomeric solutions alternating between positively charged and negatively charged solutions, for application to one or both sides of a spacer material, which is the result of transport between two opposing rotating rollers to facilitate adhesion of the solution resulting in cross-hatched or ionically charged solutions.

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