Abstract: Described are improved electrodialysis (ED) desalination systems and methods comprising voltage regulation and/or improved stack geometries. The systems and methods provide product water concentrations suitable for drinking (having a total dissolved solids concentration of less than 500 mg/L or 500 ppm) and have a high product recovery ratio.

Abstract: The present invention relates to a membrane stack and device for a membrane based process and method therefore. The membrane stack comprises: a number of membranes (78) forming compartments; and fluid supply and discharge means (80) for supplying and discharging a fluid to the compartments such that the fluid is supplied and discharged substantially in the plane of the membrane of the membrane stack. Preferably, the fluid supply and discharge means are provided on opposite sides of the membrane stack. Further, the invention relates to a method of forming the membranes (78).

Abstract: An electrical purification apparatus and methods of making same are disclosed. The electrical purification apparatus may provide for increases in operation efficiencies, for example, with respect to current efficiencies and membrane utilization.

Abstract: Electrochemical devices and methods for water treatment are disclosed. An electrodeionization device (100) may include one or more compartments (110) containing an ionselective media, such as boron-selective resin (170). Cyclic adsorption of target ions and regeneration of the media in-situ is used to treat process water, and may be driven by the promotion of various pH conditions within the electrochemical device.

Abstract: An electrical purification apparatus and methods of making same are disclosed. The electrical purification apparatus may provide for increases in operation efficiencies, for example, with respect to current efficiencies and membrane utilization.

Abstract: Membrane, cell and device suitable for reverse electrodialysis for the purpose of generating electricity, and methods therefor, the membrane comprising a number of channels arranged on at least a first side of the membrane, wherein the channels are suitable for throughfeed of a fluid, wherein the dimensions of the channels are aimed at obtaining a laminar flow of the fluid in the channels.

Abstract: An apparatus for performing electrodialysis at pressures greater than or equal to the ambient pressure is described. The apparatus includes an electrodialysis membrane stack and housing. The electrodialysis membrane stack includes at least one electrodialysis cell. The electrodialysis apparatus includes electrodes that apply voltage across the electrodialysis stack. The housing pressurizes the electrodialysis stack at a stack pressure. The housing includes a cell chamber that receives the electrodialysis stack, the cell chamber including at least one pressurization port communicating with the cell chamber such that a portion of electrode solution is transmittable into a region of the cell chamber outside the electrodialysis stack.

Abstract: An electrochemical separation system may be modular and may include at least a first modular unit and a second modular unit. Each modular unit may include a cell stack and a frame. The frame may include a manifold system. A flow distribution system in the frame may enhance current efficiency. Spacers positioned between modular units may also enhance current efficiency of the system.

Abstract: A continuous electrochemical pump comprising a water generator compartment, an anode compartment on one side of said generator compartment, a cation exchange barrier, separating the generator compartment from the anode compartment, it first electrode in electrical communication with the anode compartment, a cathode compartment adjacent the generator chamber, an anion exchange barrier, separating the generation compartment from the cathode compartment, and a second electrode in electrical communication with the cathode compartment. Use of the pump as a sample concentrator. A feedback loop for the pump. A reservoir, with or without an intermediate piston, on the output side of the pump.

Abstract: A three-electrode electrolyzer cell is described that can produce either alkaline water or acid water, by selecting polarity and ion exchange membrane type. The cell has a middle chamber and two side electrolysis chambers bordering the middle chamber. Each of the side electrolysis chambers is separated from the middle chambers by a membrane, which is the same on both sides. Porous electrodes are placed on the electrolysis side of each membrane. The electrolysis chamber electrodes are placed next to the membranes, and they are both charged with either positive or negative polarity at the same time. The electrode in the middle chamber is charged with the opposite polarity to the electrolysis chamber electrodes. Each of the electrolysis chambers has inlets and outlets for flowing a solution to be electrolyzed through the cells. The electrolyte solution is in the middle chamber. It is not circulated, or is only circulated to replenish electrolytes or remove gases.

Abstract: Dialysis treatment devices and methods for removing urea from dialysis waste streams are provided. In a general embodiment, the present disclosure provides a dialysis treatment device including a first cell having a first electrodialysis unit, a second cell having at least one of a urease compartment and a sorbent compartment and in fluid communication with the first cell, and a third cell having a second electrodialysis unit and in fluid communication with the second cell.

Abstract: Systems and methods for microbial processes of generating products such as electrical power, hydrogen gas and methane, are provided according to aspects of the present invention which include a reaction chamber having a wall defining an interior of the reaction chamber and an exterior of the reaction chamber; an anode at least partially contained within an anode compartment of the reaction chamber; a plurality of exoelectrogenic microorganisms disposed in the anode compartment; a cathode at least partially contained within a cathode compartment of the reaction chamber; a conductive conduit for electrons in electrical communication with the anode and the cathode; and a reverse electrodialysis stack comprising a plurality of plurality of alternating anion selective barriers and cation selective barriers disposed between the anode and the cathode defining one or more saline material compartments and one or more lower-saline material compartments.

Abstract: Described herein are a method and system for desalinating saltwater using concentration difference energy. A “five stream” dialytic stack is described that can be used to desalinate saltwater at a relatively high recovery ratio. The dialytic stack may include, for example, one or more drive cells having a paired concentrate and a diluent-c chamber in ionic communication with a product chamber that is adjacent to an anion and a cation discharge chamber each filled with diluent-p. The drive cell applies a drive voltage across the product chamber, and when the drive voltage exceeds a desalination voltage of the product chamber, the saltwater in the product chamber is desalinated. The dialytic stack may accept brine discharged from a first desalination plant as saltwater to be desalinated. Processing the brine in the dialytic stack may decrease its volume, decreasing costs associated with treating or otherwise disposing of the brine.

Abstract: An electrochemical separation system may be modular and may include at least a first modular unit and a second modular unit. Each modular unit may include a cell stack and a frame. The frame may include a manifold system. A flow distribution system in the frame may enhance current efficiency. Spacers positioned between modular units may also enhance current efficiency of the system.

Abstract: An electrical purification apparatus and methods of making same are disclosed. The electrical purification apparatus may provide for increases in operation efficiencies, for example, with respect to current efficiencies and membrane utilization.

Abstract: The present invention discloses a turn-back electrodeionization apparatus in which the central section of cation exchange membrane and anion exchange membrane constituting a dilute chamber is adhered along axial direction, and the dilute chamber is separated into an inner side dilute chamber unit and an outside dilute chamber unit, so that the dilute sequentially flows through the outside dilute chamber unit and inner side dilute chamber unit in a turn-back way.

Abstract: A device and process are disclosed for the separate removal of oppositely charged ions from electrolyte solutions and recombining them to form new chemical compositions. The invention provides the ability to create multiple ion flow channels and then form new chemical compositions therefrom. The process is accomplished by selectively combining oppositely charged ions of choice from different electrolyte solutions via the capacitive behavior of high electrical capacity electrodes confined in insulated containers.

Abstract: A continuous electrochemical pump comprising a water generator compartment, an anode compartment on one side of said generator compartment, a cation exchange barrier, separating the generator compartment from the anode compartment, a first electrode in electrical communication with the anode compartment, a cathode compartment adjacent the generator chamber, an anion exchange barrier, separating the generation compartment from the cathode compartment, and a second electrode in electrical communication with the cathode compartment. Use of the pump as a sample concentrator. A feedback loop for the pump. A reservoir, with or without an intermediate piston, on the output side of the pump.

Abstract: A method and apparatus for desalinating saltwater using concentration difference energy is disclosed. In order to desalinate saltwater that is contained within a product chamber, a drive cell is used to generate a drive voltage. The product chamber has a desalination voltage such that when a sufficient voltage is applied to the product chamber, anions and cations migrate out of the product chamber, thereby desalinating the water. The sufficient voltage, which includes the drive voltage and which is equal to or greater than the desalination voltage, is applied to the product chamber, consequently effecting desalination. Beneficially, concentration difference energy can be generated using a concentrated solution, which can be generated using, for example, solar energy.

Abstract: Disclosed is a system for recovering gas produced during electrodialysis of a saline solution, from gas entrained in an electrolyte solution circulating through anode and cathode compartments of an electrodialysis (ED) unit. In one embodiment, the system provides separate catholyte and anolyte towers within a closed, re-circulating loop between the cathode and anode compartments. Each tower comprises an inlet at which the entrained gas separates from the electrolyte solution and flows into the headspace. One can recover residual gases from the electrolyte solution in one more additional apparatus. Preferably, hydrogen gas is separated from the catholyte solution and, more preferably, further purified for use as a fuel source in alternative power generating devices, such as a fuel cell or bio-fuel generator, useful in the unit operations of a water treatment system.

Abstract: A non-Faraday ionic species removal process and system is described. The system includes a power supply, a pump for transporting a liquid through the system, and a plurality of porous electrodes. The electrodes , each include an electrically conductive porous portion. The electrodes may also include a substrate contiguous with the porous portion. The porous electrode can be utilized in electrodialysis and electrodialysis reversal systems. A method for forming a porous electrode is described.

Abstract: Flow-through capacitors are provided with one or more charge barrier layers. Ions trapped in the pore volume of flow-through capacitors cause inefficiencies as these ions are expelled during the charge cycle into the purification path. A charge barrier layer holds these pore volume ions to one side of a desired flow stream, thereby increasing the efficiency with which the flow-through capacitor purifies or concentrates ions.

Abstract: An improved apparatus and operating method related thereto for deionizing water to produce substantially pure water using electric field and ion exchange materials are disclosed, including embodiments incorporating one or more of the novel features of brine and electrode streams flowing in a direction counter-current to the stream being deionized, a filling of the brine stream with stratified ion exchange materials, a stream mixing feature for mixing the stream being deionized, a gas removal feature for removal of gases, a spiral-wound embodiment of an electrodialysis device according to the invention, and a method for determining the preferred operating current for electrodialysis systems according to this invention.

Abstract: In regenerating an electroless metal plating bath by electrodialysis, it has been found that the metal of the metal plating bath deposits in the electrolysis arrangement. To overcome this problem, an improvement to prior art regenerating devices is suggested, said improvement consisting in providing main cation exchangers for removing ions of this metal from a concentrate fluid. The main cation exchangers are coupled to the concentrate compartments of the electrolysis arrangement in such a manner that the concentrate fluid flowing through the concentrate compartments is allowed to pass through the main cation exchangers and to be recirculated back into the concentrate compartments.

Abstract: A system for removing contaminants from water utilizes a layered stack of anion permeable membranes and cation permeable membranes positioned between an anode and a cathode. The layered stack of membranes forms a concentrate water stream flow channel and a diluent water stream flow channel. Ion specific ion exchange resins are inserted within the diluent water stream flow channel. The water stream is pumped through the layered stack of anion permeable membranes. By using the anode, the cathode, and the voltage source to place an electrical potential gradient across the layered stack of membranes the negative ions are drawn toward the anode and the positive ions are drawn toward the cathode in the diluent water stream that flows through the diluent water stream flow channel.

Abstract: The present invention generally relates to devices able to purify fluids electrically that are contained within pressure vessels, as well as to methods of manufacture and use thereof. Liquids or other fluids to be purified enter the purification device and, under the influence of an electric field, are treated to produce an ion-depleted liquid. Species from the entering liquids are collected to produce an ion-concentrated liquid. Increasing the exterior pressure on the device may reduce the pressure difference between the interior of the device and the exterior, which may reduce manufacturing costs or simplify construction.

Abstract: An electrodeionization apparatus is provided comprising an ion-concentrating compartment partially bounded by an anion permeable membrane and also partially bounded by a cation permeable membrane, and a first ion exchange material domain disposed within the ion-concentrating compartment, wherein the first ion exchange material domain is contiguous with at least a portion of an ion-concentrating compartment side surface of one of the anion permeable membrane and the cation permeable membrane, and is spaced apart from the other one of the one of the anion permeable membrane and the cation permeable membrane. In the case where the one of the anion permeable membrane and the cation permeable membrane, having the at least a portion of an ion-concentrating compartment side surface with which the first ion exchange material domain is contiguous, is an anion permeable membrane, the first ion exchange material domain is an anion exchange material predominant domain.

Abstract: An electrodeionisation apparatus comprising, successively: means defining an anode chamber, means defining one or more anion exchange chambers, means defining one or more mixed exchange chambers, means defining one or more cation exchange chambers, and means defining a cathode chamber, the anion, mixed and cation exchange chambers providing a flow path for water to be purified, is described. The present invention incorporates advantages of both separate resin bed and mixed resin bed technology.

Abstract: A releaseable membrane structure for producing a free membrane containing a substrate, a release stratum on the substrate and a membrane stratum on the release stratum. The release stratum and the membrane stratum contain oppositely-charged polyelectrolytes that are associated. The oppositely-charged polyelectrolytes of the release stratum are selected to dissociate upon application of stimulus whereas those of the membrane stratum are selected to remain associated upon application of the stimulus. Thus, when the stimulus is applied the polyelectrolytes in release stratum dissociate and the membrane stratum is released from the substrate and is a free membrane.

Abstract: Filter or filter-element designated for Modified Electro-Dialysis (MED) purposes characterized in that the filter or filter-element comprises a porous, ceramic, mainly uniform material with functional, preferably ion selective groups grafted onto the inner, porous surface of the ceramic body. The outer surface of the filter or filter-element may be completely or partly covered by layers of porous, ceramic membranes with a pore size of less than 1 ?m and thickness less than 1 mm, and/or anion, cation or bipolar groups or membranes. The thickness of the filter-element is larger than 1 mm and has pores of size larger than 1 ?m. The invention also relates to a method for the manufacture of such a filter either continuously by tape-casting, extruding, rolling or calendaring or single-bodied by casting, pressing or forging, of a paste containing a non-conductive, ceramic material.

Abstract: A system and process for oxidizing inorganic or organic species is disclosed. The system and process includes feeding a dilute aqueous alkali metal halite solution into a cation exchange column, wherein the cation exchange column contains a cation exchange material; contacting the dilute aqueous alkali metal halite solution with the cation exchange material to produce an effluent containing halous acid; feeding the effluent containing halous acid into a catalytic reactor containing a catalytic material; and contacting the halous acid containing effluent with the catalytic material to produce a halogen oxide.

Abstract: The present invention generally provides an apparatus and method for removing contaminants from a plating solution. The apparatus generally includes a plating cell having an electrolyte inlet and an electrolyte drain, an electrolyte storage unit in fluid communication with the electrolyte inlet, and an electrodialysis chamber in fluid communication with the electrolyte drain, wherein the electrodialysis chamber is generally configured to receive a portion of used electrolyte solution and remove contaminants therefrom. The method generally includes supplying an electrolyte solution to a copper plating cell, plating copper onto a substrate in the plating cell with the electrolyte solution, removing used electrolyte solution from the plating cell, and refreshing a portion of the used electrolyte solution with an electrodialysis cell.

Abstract: Injection bonded articles comprised of a rigid core and secured together with an elastomeric material network which also forms seals and encapsulates at least a portion of the rigid core. The elastomeric material is selected to be compatible with the material comprising the rigid core to create a chemical and mechanical bond therebetween. Injection bonding and over-molding techniques are used to fabricate an electrodeionization apparatus spacer comprised of mated rigid segments secured by a unitary elastomeric material network that also forms internal and external seals that fluidly isolate one or more of inlet ports, resin cavities, and outlet ports as well as throughports. Injection bonding and over-molding techniques can also be used to fabricate other articles comprised of multiple segments.

Abstract: An electrodeionization device for large-volume ultra-pure deionization of water is disclosed. The device comprises a plurality of alternating ion depletion and concentration compartments, interposed between an anode assembly and a cathode assembly, through which flows either a product stream or a waste stream. Each compartment contains several fluid-accessible channels packed with an appropriate ion-exchange medium. The flow of the waste and product streams among the compartments is “parallel” (i.e., contemporaneous). The flow of a stream through the compartments—i.e., through the channels therein—is “serial” (i.e., sequential). In an embodiment, electrical current is generated through the compartments using segmented electrodes—either in the anode and/or the cathode assembly—that are connected to a single multiple-outlet power source.

Abstract: Silica and boron are particularly removed at high rate in processing by the electrodeionization apparatus. An electrodeionization apparatus has an anolyte compartment 17 having an anode 11, a catholyte compartment 18 having a cathode 12, concentrating compartments 15, and desalting compartments 16. The concentrating compartments 15 and the desalting compartments 16 are alternately formed between the anolyte compartment 17 and the catholyte compartment 18 by alternately arranging a plurality of anion-exchange membranes 13 and a plurality of cation-exchange membranes 14. The desalting compartments 16 and the concentrating compartments 15 are filled with ion-exchanger. The anion exchanger/cation exchanger volume ratio is 8/2 to 5/5. Electrode water flows into the anolyte compartment 17 and the catholyte compartment 18. Concentrated water is introduced into the concentrating compartments 15. Raw water is fed into the desalting compartment 16 to produce the deionized water from the desalting compartment 16.

Abstract: In a device for electro-deionization (EDI) in the demineralization of aqueous solutions, which device includes ion exchange membranes arranged alternately and in spaced relationship so that between the membranes compartments are formed of which at least some are filled with cation and anion resin exchange particle fractions forming a mixed bed ion exchanger, the ion exchange resin particles of one of the two fractions include a magnetic material and a magnetic field generator is provided for generating a field for orienting the magnetic resin particles and arranging them in parallel chains extending between the membranes.

Abstract: An electrodeionization apparatus comprising an endblock formed from a resilient material, and method for making the same. The resilient material may include various types of thermoplastic elastomers, such as, styrene block copolymers, copolyesters, plolyurethanes, polyamides, thermoplastic elastomeric olefins, and thermoplastic vulcanizates. The resilient material may have a Shore A hardness of between about 40 and about 90.

Abstract: An apparatus for the electrodialytic regeneration of an electroless bath electrolyte. There are diluate compartments through which the bath electrolyte is channeled, concentrate compartments through which a regeneration electrolyte is channeled, an anode, and a cathode. The diluate compartments of the first electrodialysis unit are serially connected to the diluate compartments of the second electrodialysis unit via lines through which the bath electrolyte is sequentially channeled. The concentrate compartments of the first electrodialysis unit are serially connected to the concentrate compartments of the second electrodialysis unit via lines through which the regeneration electrolyte is sequentially channeled.

Abstract: An electrodeionization apparatus comprising an endblock formed from a resilient material, and method for making the same. The resilient material may include various types of thermoplastic elastomers, such as, styrene block copolymers, copolyesters, plolyurethanes, polyamides, thermoplastic elastomeric olefins, and thermoplastic vulcanizates. The resilient material may have a Shore A hardness of between about 40 and about 90.

Abstract: The present invention generally provides an apparatus and method for removing contaminants from a plating solution. The apparatus generally includes a plating cell having an electrolyte inlet and an electrolyte drain, an electrolyte storage unit in fluid communication with the electrolyte inlet, and an electrodialysis chamber in fluid communication with the electrolyte drain, wherein the electrodialysis chamber is generally configured to receive a portion of used electrolyte solution and remove contaminants therefrom. The method generally includes supplying an electrolyte solution to a copper plating cell, plating copper onto a substrate in the plating cell with the electrolyte solution, removing used electrolyte solution from the plating cell, and refreshing a portion of the used electrolyte solution with an electrodialysis cell.

Abstract: An electrodeionization (EDI) module is formed from an anode spaced apart from a cathode, one or more waste channels formed between the electrodes and a product channel located inward of the waste channel(s). Ion permeable membranes form the boundary between the product channel and the waste channel(s). The product channel and waste channels are filled with a mixture of anionic and cationic ion exchange materials. At least the waste channel(s) and preferably the product channel as well, use either an anion bead having a relatively low affinity for the selected anion specie(s) to be retained (e.g. Type II) or it is a blend with Type I materials. Preferably, the membranes contain an ion exchange material to speed the transfer of ions across them. More preferably, the anionic membrane contains anion materials that have a relatively low affinity for the selected specie or species for retention.

Abstract: A bipolar membrane which exhibits a low water dissociation voltage for an extended period of time under a high current density condition, and a high current efficiency, without developing blister. The bipolar membrane comprises a cation-exchange membrane and an anion-exchange membrane which are joined together, wherein ion-exchange resin particles having ions exchanged with ions of a metal of an atomic number 20 to 90, such as titanium, zirconium, tin, iron, ruthenium or palladium, or with complex ions of said metal are existing on the junction interface between the cation-exchange membrane and the anion-exchange membrane.

Abstract: Feed water, fed through an inlet 6 into a desalting compartment 8, flows around the end 4a of a anion-exchange membrane 4 surrounding an anode 2a. The feed water enters into a portion defined between the anion-exchange membrane 4 and a cation-exchange membrane 5, and flows around the end 5a of the cation-exchange membrane 5 surrounding a cathode 3a. Then, the water to be treated further flows around the ends 4b, 5b of ion-exchange membranes 4, 5 surrounding an anode 2b and a cathode 3b, respectively, and then flows out through a product water outlet 7. A part of product water is supplied to the concentrated water circulating within the concentrating compartment 30, 40. A part of the concentrated water flowing out of the concentrating compartment 30, 40 is added to concentrated water circulating within the concentrating compartment 10, 20. The diffusion of silica from the concentrating compartment is restricted. As a result, final product water containing extremely low silica concentration is obtained.

Abstract: An electrodeionization apparatus in which enough electric current flows even when a low voltage is applied, so that it can made sufficient deionizing treatment is provided. A cation exchange membrane 3 and an anion exchange membrane 4 are arranged between a cathode 1 and an anode 2, a cathode-concentration compartment 5 is formed between the cathode 1 and the cation exchange membrane 3, an anode-concentration compartment 6 is formed between the anode 2 and the anion exchange membrane, and a desalting compartment 7 is formed between the cation exchange membrane 3 and the anion exchange membrane 4. The cathode-concentration compartment 5 and the anode-concentration compartment 6 each of which is used also as a concentrating compartment are filled with a cation exchange resin 8. The desalting compartment 7 is filled with a mixture of the cation exchange membrane 8 and an anion exchange membrane 9. Raw water is fed into the desalting compartment 7 and taken out as deionized water.

Abstract: An electrodeionization apparatus and method of use includes an expanded conductive mesh electrode. The expanded conductive mesh electrode may be formed from any conductive material that is dimensionally stable and may be coated with conductive coating suitable for use in anode or cathode service. The expanded conductive mesh electrodes are formed by slitting a sheet of metal and pulling its sides in a direction perpendicular to the slits. The fabricated mesh may be flattened after stretching. The expanded conductive mesh electrodes typically have a diamond-shaped pattern of any size that provides support for an adjacent ion-permeable membrane while allowing an electrode or fluid stream to flow through. The mesh size typically has a long-wise dimension and a short-wise dimension. The conductive mesh electrode may also be placed against an endblock having fluid channels. These channels may be serpentine or parallel channels, which allow fluid flow to wash away any accumulation.

Abstract: Process for the manufacture of alkali metal hydroxide, according to which an electrodialysis cell containing three compartments is used, an aqueous alkali metal halide solution is circulated in a saline compartment of the cell, delimited between an anionic membrane and a cationic membrane, an alkali metal halide is introduced into an acidic compartment of the cell, delimited between the anionic membrane and a cationic face of a bipolar membrane and an aqueous alkali metal hydroxide solution is extracted from an alkaline compartment of the cell, delimited between the cationic membrane and an anionic face of the bipolar membrane.

Abstract: A porous immobilized ion-exchange material is provided. Also provided is an electrodeionization device incorporating the material. A method for subjecting a fluid to electrodeionization, is provided utilizing porous immobilized ion-exchange material. A salient feature of the material is that it can be regenerated in situ.

Abstract: An electrodeionisation apparatus comprising a first deionising flow path and an integral second deionising flow path is described. The outflow from the first path is held in a holding tank prior to passage through the second flow path, and the outflow from the second path is available for use. Optionally, the second path outflow is partly or fully returned to the holding tank. Me recirculation of the already purified water in the holding tank maintains the water in the holding tank at a higher standard than otherwise “standing” purified water. The water in the holding tank could be separately made available for use. The apparatus requires the use of only a single pair of electrodes and hence one power supply. Moreover, the ion exchange materials in the first deionising flow path can be regenerated when water is not flowing through them such that they have a greater capacity for deionisation when required.

Abstract: A method of treating an acid treatment solution which includes steps of adding sulfuric acid to an acid treatment solution which contains therein non-alkaline metal ions to produce sulfate, and recovering the regenerated acid treatment solution from the acid treatment solution to which the sulfuric acid has been added by separating the sulfate therefrom. Also, a device for realizing the method, and a method of fabricating a support for a planographic printing plate using the same.

Abstract: An electro-regenerating type apparatus for producing deionized water, which comprises an electrodialyzer having cation exchange membranes and anion exchange membranes alternately arranged between an anode compartment provided with an anode and a cathode compartment provided with a cathode, demineralizing compartments compartmentalized with the anion exchange membranes on the anode side and compartmentalized with the cation exchange membranes on the cathode side, and concentrating compartments compartmentalized with the cation exchange membranes on the anode side and compartmentalized with the anion exchange membranes on the cathode side, the electrodialyzer having ion exchangers accommodated in the demineralizing compartments, wherein a porous anion exchanger layer having a porosity of from 20 to 95%, a maximum pore size of from 0.01 to 500 &mgr;m and a thickness of at least five times the maximum pore size and from 10 &mgr;m to 10 mm, is provided on the anode side of each anion exchange membrane.