Title of Invention: METHOD OF MANUFACTURING CA- PACITIVE DEIONIZATION ELECTRODE HAVING ION SELECTIVITY AND CDI ELECTRODE MODULE INCLUDING

THE SAME

Technical Field

[1] The present invention relates to a method of manufacturing an ion selective ca- pacitive deionization electrode, more particularly, to a method of manufacturing the capacitive deionization electrode where cations and anions may be separated and removed efficiently due to ion selectivity, and an ion selective layer of the electrode may be crosslinked to improve durability.

[2] Furthermore, the present invention relates to a CDI electrode module including the ion selective capacitive deionization electrode.

Background Art

[3] A deionization technology in production of municipal water or industrial water has a very important role in determining human health, process efficiency or product capability. When people drank water containing a heavy metal, or a nitric nitrogen ion or a fluorine ion for a long period of time, the water may have a harmful effect on the human body.

[4] Furthermore, since boiler water containing hardness materials may cause a scale in a boiler or a heat exchanger to significantly decrease product efficiency, ultrapure water in which ion materials are removed completely serves as an important factor to determine a product capability even in electronics industry or pharmaceutical industry.

[5] Presently, an ion exchange method using an ion exchange resin has been widely used as a method of removing an ionic material from an aqueous solution. The method may effectively separate most of the ionic materials, but there is a problem where a large amount of acids, bases, or waste solutions of salts occur in a reuse process of an ion exchanged resin. In addition, membrane technologies such as reverse osmosis or elec- trodialysis have been applied, but there are problems such as reduction of process efficiency caused by membrane fouling, cleaning of contaminated membrane, or regular change of a membrane. In order to address such problems of the conventional deionization technology, a capacitive deionization technology using the principle of an electric double layer have been studied and applied to a deionization process recently.

[6] The capacitive deionization operates at a low electrode potential (about 1 to 2 V) because adsorption reaction of ions is carried out by an electrical attractive force in an electric double layer formed on the surface of the electrode, when a potential was applied to an electrode. As a result, the capacitive deionization has a significantly low energy consumption amount compared to other deionization technologies, and thus, has been evaluated as a low energy consumption type next generation deionization technology.

[7] The gist of the capacitive deionization technology is to develop an electrode where a capacitance may be improved significantly. Since 1990, a study of an electrode which is manufactured by using carbon-based materials such as an activated carbon powder, an activated carbon fiber, a carbon nanotube and a carbon aerogel, in which the electrode has a good electric conductivity and a high specific surface area has been actively underway. However, in case of the electrode thus manufactured, there is a limitation in improving an electrode capability, because a capacitance is determined in accordance with type and features of carbon, and a content ratio thereof.

[8] Furthermore, when adsorbed ions reach a capacitance of the electrode and then an electrode potential is changed to 0 V or a reversal potential, the adsorbed ions are allowed to desorb, and thus the electrode may be reused. At this time, the ions adsorbed to the electrode are desorbed due to change of an electrode potential, and the ions migrate to the surface of opposite electrode to form an electric double layer. Herein, there is a problem where the adsorbed ions are not all desorbed, and the ions remain on the surface of opposite electrode, to thereby reduce an adsorption efficiency of the electrode.

[9] On the other hand, Korean Patent Laid-open Publication No. 10-2010-0021265

discloses a method of producing an ion exchange membrane, an efficiency of a unit cell may be improved by using an anion exchange membrane and a cation exchange membrane having an ion selectivity. However, when the electrode is used in a module, the number of stacked electrodes decreases to decrease an instant treatment flow rate, a high cost of commercially available ion exchange membrane results in a higher manufacturing cost of the capacitive deionization electrode module, and a production process is more complicated.

[ 10] [Related Art Document]

[11] [Patent Document]

[12] (Patent Document 1) Korean Patent Laid-open Publication No. 10-2010-0021265 (2010.02.24)

Disclosure of Invention

Technical Problem

[13] An object of the present invention is to provide a method of manufacturing an ion selective capacitive deionization electrode by which adsorption removal efficiency is increased and durability on the surface of the electrode is improved. More specifically, a problem where, in a process of desorbing the adsorbed ions, opposite charge ions migrate to a counter electrode or an ion selective coating layer is damaged, thus reducing an adsorption efficiency of the electrode is addressed, and therefore there is provided a method of manufacturing an ion selective capacitive deionization electrode having a good adsorption and desorption efficiency of ions and a good durability.

[14] Furthermore, another object of the present invention is to provide a CDI electrode module formed by stacking an ion selective capacitive deionization electrode with a spacer sequentially, and packing the stack in a case equipped with an inlet and an outlet of dissolved ion water.

Solution to Problem

[15] The present invention for achieving the object relates to a method of manufacturing a new ion selective capacitive deionization electrode.

[16] Specifically, the present invention relates to a method of manufacturing a ion

selective capacitive deionization electrode by adding an ion exchange resin, a solvent, a crosslink agent, and a polymerization initiator to prepare a ion selective polymer matrix solution; coating the surface of an active layer with the solution and

crosslinking the coated surface, to form an ion selective layer, in which the electrode has a good durability and is capable of efficiently separating and removing cations and anions without using cationic and anion exchange membranes.

[17] In one general aspect, a method of manufacturing an ion selective capacitive

deionization electrode includes steps of:

[18] (a) producing a first composition containing at least one resin selected from an ion exchange resin, a crosslinkable ion exchange resin and a non-ionic resin, and an electrode active material;

[19] (b) applying the first composition on a collector or performing calendering

processing to form an active layer; and

[20] (c) coating the surface of the active layer with an ion selective polymer matrix

solution containing a crosslinkable ion exchange resin, a crosslinking agent, monomer and a polymerization initiator, and crosslinking the coated surface to form an ion selective layer.

[21] After step (c), the method further may include (d) pressing.

[22] Furthermore, in another general aspect, a CDI electrode module is formed by

stacking an ion selective capacitive deionization electrode with a spacer sequentially, and packing the stack in a case equipped with an inlet and an outlet of dissolved ion water.

[23] Each configuration will be described in detail below. [24] The ion exchange resin in step (a) includes a cation exchange resin with a cation exchange group, or an anion exchange resin with an anion exchange group. The cation exchange resin includes any one cation exchange group selected from a sulfonic acid group, a carboxyl group, a phosphonic group, a phosphinic group, an asonic group and a selinonic group. The anion exchange resin includes any one anion exchange group selected from a quaternary ammonium salt, primary to tertiary amine, a quaternary phosphonium group and a tertiary sulphonium group. Specific examples thereof that may be used include any one or a mixture of two or more resins selected from polystyrene, polysulfone, polyether sulfone, polyamide, polyester, polyimide, polyether, polyethylene, polytetrafluoroethylene, trimethylammonium chloride, and polyglycidyl methacrylate. Furthermore, the resin is not limited as long as the resin may have a cation exchange group or anion exchange group.

[25] Furthermore, when, in step (a), a crosslinkable ion exchange resin is included, a crosslinking agent, monomer, and a polymerization initiator may be included.

[26] The crosslinkable ion exchange resin includes a crosslinkable functional group, with a cation exchange group or an anion exchange group. The cation exchange group may include any one selected from a sulfonic acid group, a carboxyl group, a phosphonic group, a phosphinic group, an asonic group and a selinonic group. The anion exchange group may include any one selected from a quaternary ammonium salt, primary to tertiary amine, a quaternary phosphonium group and a tertiary sulphonium group. The crosslinkable functional group may include at least one selected from a hydroxyl group, an amine group, an isocyanate group, a urea group, an epoxy group, a chloromethyl group and a vinyl group. Specifically, for example, any one or a mixture of at least two resins (i.e., those selected from polystyrene, polysulfone, polyether sulfone, polyamide, polyester, polyimide, polyether, polyethylene, polytetrafluoroethylene, trimethylammonium chloride, polyglycidyl methacrylate and a copolymer of these compounds), in which one or more functional groups are substituted with any one or two or more crosslinkable functional groups (i.e., those selected from a hydroxyl group, an amine group, an isocyanate group, a urea group, an epoxy group, a chloromethyl group, and a vinyl group), may be used.

[27] Furthermore, the resin may be used without limitation as long as the resin may have a crosslinkable functional group with a cation exchange group or an anion exchange group.

[28] The crosslinking agent includes a functional group in which condensation reaction or addition reaction may be carried out, and preferably a functional group in which an ester bond, an epoxy bond, or urethane bond may be formed. For example, it is preferable that the crosslinking agent include at least one or two selected from a hydroxyl group, an amine group, a carboxyl group, a vinyl group, an epoxy group, a urea group, a chloromethyl group and an isocyanate group. Examples of the crosslinking agent include at least one or two selected from ethyl eosin,

2,2-dimethoxy-2-phenyl acetophenone, 2-methoxy-2-phenylacetophenone,

2-hydroxy- 1 - [4-(2-hydroxyethoxy)phenyl] -2-methyl- 1 -propanone, N-methylolurea, N- methylol melamine, diisocyanate, isocyanate, diethylenetriamine, triethylenetetramine, phthalic acid anhydride, methyl tetrahydrophthalic acid anhydride, methyl nasic acid anhydride, pyromellitic acid anhydride, 4-chloromethyl styrene, succinic acid anhydride, ethylene glycol, 3,3'5,5'-tetramethyl benzidine,

N,N'-bis-trityl-hexane-l,6-diamine, l,5-diamino-2-methyl-pentane and hexamethylene diisocyanate. The crosslinking agent may be used without limitation as long as the crosslinking agent has a functional group which is able to form a crosslinking bond.

[29] The monomer is crosslinked with a crosslinking agent to improve durability of the active layer, and preferably a monomer having a double bond structure. Specific examples of the monomer that may be used include at least one or two selected from methyl methacrylate, styrene, ethyl acrylate, hydroxyethyl acrylate, isopropyl acrylate, 4-chloromethyl styrene, n-butyl acrylate, n-hexyl methacrylate, 2-ethyl hexyl acrylate, ethyl methacrylate, acrylic acid, methacrylic acid, maleic acid, 2-hydroxyl ethyl methacrylate, and the like, but is not limited thereto.

[30] The polymerization reaction initiator may include a thermal polymerization initiator and a photopolymerization initiator. Examples of the thermal polymerization initiator that may be used include any one or a mixture of at least two selected from sodium persulfate, potassium persulfate, ammonium persulfate, hydrogen peroxide,

2,2-azobis-(2-amidinopropane)dihydrochloride, 2,2-azobis-(N,N-dimethylene) isobu- tyramidine dihydrochloride, 2-(carbamoylazo)isobutyronitrile,

2,2-azobis[2-(2-imidazolin-2-yl)propane] dihydrochloride, benzoylperoxide,

4,4-azobis-(4-cyanovaleric acid) and ascorbic acid. Examples of the photopolymerization initiator that may be used include any one or a mixture of at least two selected from benzoin ether, benzophenone, dialkylacetophenone, hydroxyl alkyl ketone, phenyl glyoxylate, benzyl dimethyl ketal, camphorquinone, acyl phosphine, and a-aminoketone. An amount of the polymerization initiator which may be added is in a range of 0.05 to 20 parts by weight when the total amount of the ion exchange resin and monomer is set to 100 parts by weight. This is because the polymerization initiator that is added in the range described above helps to activate crosslinking reaction, and thus may have a higher degree of crosslinking.

[31] The crosslinking may be carried out by thermal polymerization or photo- polymerization. When the crosslinking reaction is carried out by thermal polymerization, a crosslinking reaction and organic solvent removal are performed by normal pressure drying or vacuum drying under a temperature atmosphere of room temperature to 200°C. A crosslinking reaction time and solvent removal time are determined in accordance with crosslinking reaction rate and type of solvents to be used.

[32] When the crosslinking reaction is carried out by photo-polymerization, light radiation amount may be in a range of 200 to 50,000 mJ/cm ² . When the light radiation amount is less than 200 mJ/cm ² , durability of the active layer cannot be improved due to insufficient crossrinking reaction. When the amount is more than 50,000 mJ/cm ² , mechanical properties on the surface of the membrane are degraded, which is not preferable. Furthermore, light radiation time may be in a range of 10 to 3,600 seconds, but the light radiation time may be varied depending on a light radiation amount. When the light radiation time is shorter than 10 seconds, the light radiation time has a small crosslinking effect. When the light radiation time is longer than 3,600 seconds, the active layer may be broken easily due to too high photo-crosslink.

[33] When photo-crosslinking reaction is carried out, a crosslinkable functional group is included by 1 to 10% in a crosslinking agent. When the crosslinkable functional group is 1 % or less, mechanical properties are degraded due to low degree of crosslinking, and durability to a shearing force caused by water flow is decreased due to high water absorption ratio. When the crosslinkable functional group is more than 10%, excessive crosslinking results in forming a hard and brittle active layer, which is not preferable.

[34] Furthermore, the resin in step (a) refers to a resin where a non-ionic resin is added, mixed with an electrode active material, to be capable of manufacturing an ion selective capacitive deionization electrode. Specific examples thereof that may be used include any one or a mixture of at least two selected from polyvinylidene fluoride, polystyrene butadiene rubber, polytetrafluoride ethylene, and polyurethane, but is not limited thereto.

[35] Furthermore, a weight average molecular weight of the ion exchange resin having an ion exchange group, the crosslinkable ion exchange resin containing a crosslinkable functional group, or the non-ionic resin is, but not limited to, preferably 50,000 to 4,000,000, and more preferably 100,000 to 1,500,000. This is because, when a polymer resin of this range was used, a good bond between an electrode active material and at least one selected from an ion exchange resin and a non-ionic resin is formed, and thus a viscosity of a first composition may be improved.

[36] In step (a), the ion exchange resin having an ion exchange group, the crosslinkable ion exchange resin or the non-ionic resin may be dissolved in a solvent. The solvent may be selected depending on type of the polymer resin. Examples of the solvent include any one or a mixture of at least two selected from distilled water, alcohol, dimethyl formamide, dimethyl acetamide, N-methyl-2-pyrrolidone acetone, chloroform, dichloromethane, trichloroethylene, ethanol, methanol and normal hexane, but are not limited thereto. [37] In step (a), the crosslinkable ion exchange resin is used, the salt removal rate and ion exchange capacity is higher than others. It is better than about 5%.

[38] The electrode active material may include an active carbon-based material having a high specific surface area, and may use any one or a mixture of at least two selected from activated carbon powder, an activated carbon fiber, a carbon nanotube and a carbon aerogel. Further, the electrode active material may include metal oxide-based materials, for example, any one or a mixture of at least two selected from Ru0 ₂ , Ni(OH) ₂ , Mn0 ₂ , Pb0 ₂ , and Ti0 ₂ . Such an electrode active material is used to control a content range depending on desire physical properties. It is preferable that 600 to 900 parts by weight of the electrode active material is used with respect to 00 parts by weight of the ion exchange resin or non-ionic resin in order to improve a capacitance of the ion selective capacitive deionization electrode. Furthermore, an average particle size of the electrode active material is 10 p or lower, more preferably 10 nm to 10 pm, but is not limited thereto. The electrode active material of this range may be used to improve a capacitance and a specific surface area of the ion selective capacitive deionization electrode.

[39] Further, the first composition may further contain a conductive material. This is because addition of the conductive material to the first composition may improve a capacitance and a specific surface area of the ion selective capacitive deionization electrode, and an electrical conductivity. The conductive material is not limited as long as it has a low electric resistance. Examples of the conductive material that may be used include at least one or two conductive carbon blacks selected from acetylene black, Ketjen black, XCF carbon and SRF carbon. The conductive material is used to control a content range thereof depending on desire physical properties. The conductive material may be used in a rang e of 1 to 10 part(s) by weight with respect to 100 parts by weight of the electrode active material to improve a electric conductivity and a capacitance of the ion selective capacitive deionization electrode, but the amount is not limited thereto. Furthermore, an average particle size of the conductive material is, but not limited to, 1 pm or lower, and preferably 10 nm to 1 pm, which is effective to increase an electric conductivity.

[40] When the first composition is prepared in step (a), a solid content is preferably 1 to 30 wt%, and more preferably 3 to 10 wt%. When the solid content is in this range, a viscosity of a polymer solution is suitable, which is easy to apply the polymer solution on a collector or perform calendering in step (b).

[41] In the step (b), an active layer is formed by applying the first composition prepared in step (a) on a collector, or performing calendering processing.

[42] It is preferable that the collector be allowed to distribute an electrical filed homogeneously on the surface of the ion selective capacitive deionization electrode, when a current is supplied to the electrode with a power supply. In addition, it is preferable that the collector has a good conductivity. Examples of the collector may include any one selected from a sheet, a thin film, or a woven metal mesh which contains aluminum, nickel, copper, titanium, iron, stainless steel, or graphite or a mixture of these metals.

[43] Examples of a method of applying the first composition on the collector include at least one or two selected from spray, dip coating, knife casting, doctor blade and spin coating, but are not limited thereto. Furthermore, a coating thickness is preferably in a range of 50 to 300 jum, which is because the ion selective capacitive deionization electrode has a lower electric resistance and higher deionization efficiency. However, number of applying the first composition on the collector is not limited, and if necessary, it is performed repeatedly one or more times to manufacture an electrode having a specific thickness.

[44] Further, when the calendering processing is used to form an active layer on a

collector, a carbon sheet may be stacked to the collector. In order to stack the first composition over the carbon sheet-stacked collector, the first composition may be kneaded with a dispersion kneader, but is not limited thereto. When kneading is performed, the active material or conductive material may be kneaded with an organic solution ion in which ion exchange resin or non-ionic resin is dissolved, after dry kneading. At this time, an ion exchange resin or non-ionic resin is impregnated into the electrode active material or conductive material.

[45] When the first composition is kneaded, a kneader temperature and kneading time may be varied depending on an ion exchange resin or a non-ionic resin included in the first composition.

[46] The kneader temperature may be in a range of glass transition temperature to melting temperature of ion exchange resin or non-ionic resin. When the kneader temperature may be 10°C higher than the glass transition temperature, more preferably 20°C higher than the glass transition temperature. This is because when the kneader temperature is lower than the glass transition temperature, a resin is hardly mixed due to higher viscosity, and is not softened and thus the surface of a carbon sheet becomes uneven. Additionally, when the kneader temperature is higher than the melting temperature, it may be difficult to manufacture a carbon sheet in a roll shape, because a resin is softened actively, and thereby a carbon sheet is attached to the surface of a roll at the time of a calendering processing, and a carbon sheet is broken due to a lower tension, and therefore a winding process is difficultly performed.

[47] The kneading time needs 5 minutes to 5 hours, preferably 30 minutes to 120 minutes.

[48] The kneader preferably includes a type equipped with an impeller, or a roll kneader, but is not limited as long as the kneader is allowed to knead homogeneously. [49] An amount of raw materials added to the kneader may be more than 10 volume% of a mixer volume, preferably 15 to 50 volume%.

[50] The first composition thus obtained may be subjected to a calendering processing directly, but may be formed in a specific size so as to handle easily. However, a method of forming the first composition is not particularly limited as long as the method may form a certain shape.

[51] The step (c) includes coating the surface of the active layer with an ion selective polymer matrix solution which contains a crosslinkable ion exchange resin, a crosslinking agent, monomer and a polymerization initiator, and crosslinking the coated surface to form an ion selective layer. The crosslinkable ion exchange resin includes a crosslinkable functional group with a cation exchange group or an anion exchange group. The crosslinkable ion exchange resin includes at least one or two crosslinkable functional groups selected from a hydroxyl group, an amine group, an isocyanate group, a urea group, an epoxy group, a chloromethyl group and a vinyl group, with any one the cation exchange group selected from a sulfonic acid group, a carboxyl group, a phosphonic group, a phosphinic group, an asonic group and a selinonic group; or any one anion exchange group selected from a quaternary ammonium salt, primary to tertiary amine, a quaternary phosphonium group and a tertiary sulphonium group. Specific examples of the resin include, any one or a mixture of at least two (i.e. those selected from polystyrene, polysulfone, polyether sulfone, polyamide, polyester, polyimide, polyether, polyethylene, polytetrafluoroethylene, trimethylammonium chloride, polyglycidyl methacrylate and a copolymer of these compounds), in which one or more functional groups are substituted with any one or two or more crosslinkable functional groups (i.e., those selected from a hydroxyl group, an amine group, an isocyanate group, a urea group, an epoxy group, a chloromethyl group, and a vinyl group), may be used.

[52] Furthermore, the resin is used without limitation as long as the resin may have a crosslinkable functional group with a cation exchange group or an anion exchange group.

[53] The crosslinking agent includes a functional group in which condensation reaction or addition reaction may be carried out, and preferably a functional group in which an ester bond, an epoxy bond, or a urethane bond may be formed. For example, it is preferable the crosslinking agent includes at least one or two selected from a hydroxyl group, an amine group, a carboxyl group, a vinyl group, an epoxy group, a urea group, a chloromethyl group and an isocyanate group. Examples of the crosslinking agent include at least one or two selected from ethyl eosin, 2,2-dimethoxy-2-phenyl ace- tophenone, 2-methoxy-2-phenylacetophenone,

2-hydroxy- 1 -[4-(2-hydroxyethoxy)phenyl]-2-methyl- 1 -propanone, N-methylolurea, N- methylol melamine, diisocyanate, isocyanate, diethylenetriamine, triethylenetetramine, phthalic acid anhydride, methyl tetrahydrophthalic acid anhydride, methyl nasic acid anhydride, pyromellitic acid anhydride, 4-chloromethyl styrene, succinic anhydride, ethylene glycol, 3,3'5,5'-tetramethyl benzidine, N,N'-bis-trityl-hexane-l ,6-diamine, l,5-diamino-2-methyl-pentane and hexamethylene diisocyanate. The crosslinking agent may be used without limitation as long as the crosslinking agent has a functional group which is able to form a crosslinking bond.

[54] The monomer is crosslinked with a crosslinking agent to improve durability, and preferably a monomer having a double bond structure. Specific examples of the monomer that may be used include at least one or two selected from methyl methacrylate, styrene, ethyl acrylate, hydroxyethyl acrylate, isopropyl acrylate, 4-chloromethyl styrene, n-butyl acrylate, n-hexyl methacrylate, 2-ethyl hexyl acrylate, ethyl methacrylate, acrylic acid, methacrylic acid, maleic acid, 2-hydroxyl ethyl methacrylate, and the like, but is not limited thereto.

[55] The polymerization reaction initiator may include a thermal polymerization initiator and a photopolymerization initiator. Examples of the thermal polymerization initiator include any one or a mixture of at least two selected from sodium persulfate, potassium persulfate, ammonium persulfate, hydrogen peroxide,

2,2-azobis-(2-amidinopropane)dihydrochloride, 2,2-azobis-(N,N-dimethylene) isobu- tyramidine dihydrochloride, 2-(carbamoylazo)isobutyronitrile,

2,2-azobis[2-(2-imidazolin-2-yl)propane] dihydrochloride, benzoylperoxide,

4,4-azobis-(4-cyanovaleric acid) and ascorbic acid. Examples of the photopolymerization initiator include any one or a mixture of at least two selected from benzoin ether, benzophenone, dialkylacetophenone, hydroxyl alkyl ketone, phenyl glyoxylate, benzyl dimethyl ketal, camphorquinone, acyl phosphine, and a-aminoketone. This is because the polymerization initiator which may be added is in a range of 0.05 to 20 parts by weight when the total amount of the ion exchange resin and monomer is set to 100 parts by weight. This is because the polymerization initiator that is added in the range described above helps to activate crosslinking reaction, and thus may have a higher degree of crosslinking.

[56] Furthermore, examples of the solvent that may be used include any one or a mixture of at least two selected from distilled water, alcohol, dimethyl formamide, dimethyl acetamide and N-methyl-2-pyrrolidone.

[57] When the ion selective polymer matrix solution is applied on the active layer, spray, dip coating, knife casting, doctor blade and spin coating may be used, but are not limited thereto. Furthermore, the ion selective capacitive deionization electrode having a coating thickness of 2 to 300 μπι, preferably 20 to 50 results in decreasing electric resistance and improving deionization efficiency. [58] The crosslinking may be carried out by thermal polymerization or photo- polymerization. When the crosslinking reaction is carried out by thermal polymerization, a crosslinking reaction and organic solvent removal are performed by normal pressure drying or vacuum drying under a temperature atmosphere of room temperature to 200°C. A crosslinking reaction time and solvent removal time are determined in accordance with crosslinking reaction rate and type of solvents to be used. With respect to one example, when a drier has a length of 5.0 m, it is preferable that a crosslinking reaction is carried out while a traveling speed of the drier is set to 0.05 to 10 m/min. When a crosslinking reaction is carried out at a traveling speed of 0.05 m/ min or lower, the ion selective capacitive deionization electrode may be overdried to remove an active layer from a collector. When a crosslinking reaction is carried out at a traveling speed of 10.0 m/min or higher, there is a problem where the electrode cannot maintain a shape thereof because the electrode is attached to an active layer due to insufficient evaporation of solvent.

[59] Furthermore, when a crosslinking reaction is carried out by photo-polymerization, a chain is broken by light radiation to form a radical, and thereby a crosslinking reaction is carried out with the radical in a reaction system. The light radiation may use light in an ultraviolet (UV) region, more preferably light in a wavelength range of 100 to 600 nm.

[60] At this time, light radiation amount may be in an amount of 200 to 50,000 mJ/cm ² .

When the amount is less than 200 mJ/cm ² , durability of the coating layer cannot be improved due to insufficient crossrinking reaction. When the amount is more than 50,000 mJ/cm ² , mechanical properties on the surface of the membrane are degraded, which is not preferable. Furthermore, light radiation time may be in a range of 10 to 3,600 seconds, but it may be varied depending on a light radiation amount. The light radiation time shorter than 10 seconds has a small crosslinking effect. When the light radiation time is longer than 3,600 seconds, an active layer may be broken easily due to excessive photo-crosslinking.

[61] When photo-crosslinking reaction is carried out, a crosslinkable functional group is included by 1 to 10% in a crosslinking agent. When the crosslinkable functional group is 1% or less, mechanical properties is degraded due to low degree of crosslinking, and durability to a shearing force caused by water flow is decreased due to high water absorption ratio. When the crosslinkable functional group is more than 10%, excessive crosslinking results in forming a hard and brittle coating layer, which is not preferable.

[62] The present invention may further include, after step (c), (d) pressing if necessary in order to obtain a constant thickness of the ion selective capacitive deionization electrode and smoothness on the surface of the ion selective capacitive deionization electrode. With respect to compressibility at the time of pressing, it is preferable that a thickness of the ion selective capacitive deionization electrode manufactured in step (c) is compressed by about 1 to 25%. When the electrode is compressed in this range, the ion selective capacitive deionization electrode has an even surface, and a sufficient density of the electrode active material, and thus may have a higher durability.

[63] In the present invention, the ion selective capacitive deionization electrode coated with an ion exchange resin having a cation exchange group may be used as a negative electrode and the ion selective capacitive deionization electrode coated with an ion exchange resin having an anion exchange group may be used as a positive electrode.

[64] Furthermore, the present invention relates to a CDI electrode module including the ion selective capacitive deionization electrode thus produced, more specifically a CDI electrode module formed by stacking an ion selective capacitive deionization electrode with a spacer sequentially, and packing the stack in a case equipped with an inlet and an outlet of dissolved ion water.

[65] Furthermore, the present invention relates to a CDI electrode module integrally

formed by connecting two or more of the CDI electrode modules to each other.

[66] FIG. 1 is an exploded diagram of a module to be assembled, FIG. 2 is a cross- sectional view of the assembled module, FIG. 3 is a three-dimensional diagram of a module case, and FIG. 4 is a type where two or more CDI electrode modules are connected to each other. As shown in FIG. 1, the module is a space configured to be divided into a first chamber 60 and a second chamber 70, in which the fist chamber include an inlet 20 of raw water and an outlet 10 of treated water, and the second chamber includes an inlet 21 of raw water and an outlet 11 of treated water which are respectively disposed at a separate wall 80 in the same position as the inlet 20 and the outlet 10 of the first chamber. Therefore, respective inlets of raw water are allowed to flow while forming the same path and respective outlets of treated water are allowed to flow while forming the same path. As shown in FIG. 3, a positive electrode terminal block 51 and a negative electrode terminal block 52 in the first chamber may be mounted in the same one direction, and a positive electrode terminal block 51 and a negative electrode terminal block 52 in the second chamber are mounted in the same one direction.

[67] A type integrally formed by connecting two or more CDI electrode modules to each other as shown in FIG. 4 may be used for advanced water treatment and high volume water purification treatment without complex pipes. Specifically, since the amount of water treated is small in one CDI electrode module, a module integrally formed by connecting two or more CDI electrode modules may be used. Thereby, the CDI electrode module which may be used for advanced water and the large amount of water treated in a small space without a pipe may be manufactured, and therefore a treated water capacity may be increased depending on a size of module, thus resulting in being capable of higher size.

[68] Furthermore, FIG. 5 shows a stacking order of complex electrodes. As shown in FIG.

5, in a stacked complex electrode module, a spacer 56 is disposed between a positive electrode 55 and a negative electrode 57. The spacer 56 separates the positive electrode 55 and a negative electrode 57 from each other to form a flow path capable of flowing water therebetween. The spacer 56 may be a non-woven fabric or a thinly woven fabric mesh fabric so as to form a flow path capable of flowing water.

[69]

Advantageous Effects of Invention

[70] The ion selective capacitive deionization electrode of the present invention is manufactured by coating the active layer with ion selective polymer matrix solution, and crosslinking the coated active layer by photopolymerization and thermal polymerization to form an ion selective layer, in which the electrode has a higher durability on the surface of the electrode as well as higher adsorption removal efficiency of the electrode. Further, there were problems such as decrease of ion selectivity as the increase of water content ratio by introducing an ion exchange group; and damage of coating layer due to shearing force of water flow, but water content ratio and durability can be improved through a crosslinking reaction. Particularly electrode resistance is decreased and an adsorption capability can be improved by introduction of a number of ion exchange groups. Further, a distance between electrodes can be minimized because an ion exchange membrane is not used, and the surface of the active layer was crosslinked to form an ion selective layer, and thereby deterioration of surface smoothness is prevented by the electrode active material. Accumulation of fouling as use of a long period of time is prevented, and peeling of electrode active material is prevented. Therefore, even though a module having a large number of stacking structures is manufactured, the module can be used stably for a long period of time, and there is an advantage to have a higher product reliability. Therefore, the electrode can have a larger size, and thereby adsorption of ionic materials can be performed more rapidly and effectively.

Brief Description of Drawings

[71] The above and other objects, features and advantages of the present invention will become apparent from the following description of preferred embodiments given in conjunction with the accompanying drawings, in which:

[72] FIG. 1 is an exploded diagram of a CDI electrode module to be assembled;

[73] FIG. 2 is a cross-sectional view of the assembled CDI electrode module;

[74] FIG. 3 is a three-dimensional diagram of a CDI electrode module case;

[75] FIG. 4 is a type where two or more CDI electrode modules are connected to each other;

[76] FIG. 5 shows a stacking order of ion selective capacitive deionization electrode;

[77] FIG. 6 is a result of analyzing a molecular weight (a) of the prepared polymer

powder when a negative electrode is manufactured by using a cation selective resin in Example 1, and a molecular weight (b) of the prepared polymer powder when a positive electrode is manufactured by using an anion selective resin in Example 1, with Gel Permeation Chromatography (GPC) (Model Waters 2690, solvent; THF, polystyrene Mw = 7,000,000);

[78] FIG. 7 is a graph obtained by analyzing an anion selective polymer matrix solution prepared in Examples 1 and 2 with IR;

[79] FIG. 8 is a TDS conversion curve according to Example 1 and Comparative Example 1; and

[80] FIG. 9 is a scanning electronic microscope image of the crosslinked ion selective capacitive deionization electrode (a) and the non-crosslinked ion selective capacitive deionization electrode (b) which is subjected to adsorption and desorption experiments in a 100 ppm of NaCl solution in a flow rate of 70 ml/min at 80°C for one month.

[81]

[82] [Detailed Description of Main Elements]

[83] 10: first chamber outlet 20: first chamber inlet

[84] 11 : second chamber outlet 21 : second chamber inlet

[85] 30: first chamber case cover 40: second case chamber cover

[86] 50: stacked electrode

[87] 51 : positive electrode terminal block

[88] 52: negative electrode terminal block

[89] 55: positive electrode 56: spacer

[90] 57: negative electrode

[91] 60: stack space of electrode (first chamber)

[92] 70: stack space of electrode (second chamber)

[93] 80: partition wall between first chamber and second chamber

[94] 90: bolt fastener 100: O-ring

[95] 110: stack space of electrode (third chamber)

[96] 120: stack space of electrode (fourth chamber)

[97] 130: stack space of electrode (fifth chamber)

[98] 140: stack space of electrode (sixth chamber)

[99] 150: fourth chamber case cover

[100] 160: sixth chamber case cover

[101] Mode for the Invention

[102] Hereinafter, a detailed description of the present invention will be provided by way of an example. However, the present invention is not limited to the following

Examples.

[103] Hereinafter, physical properties were measured as follows.

[ 104] 1. Analysis of Membrane Properties

[ 105] ( 1 ) Measurement of Ion Exchange Capacity

[106] In order to measure an ion exchange capacity, an ion exchange capacity was determined with the following Equation by acid-base titration using IN NaOH aqueous solution and IN HC1 aqueous solution. In case of anion exchange membrane, an ion exchange capacity was determined by changing the order of NaOH and HC1.

[107] IEC (meq/g)={(V _HC , x N _H ci)-5(V _Na0H x N _Na0H )} /Weight of sample(g)

[108] IEC: ion exchange capacity (meq/g)

[109] V _Ha : volume of HCl (ml), V _NaOH : volume of NaOH (ml)

[110] Ν _Ηα : concentration of HCl (N), N _Na0H : concentration of NaOH (N)

[111] (2) Water Content Ratio Measurement

[112] An ion exchange membrane was cut to a specific size (3 x 3 cm), and immersed in a 0.1 M NaCl solution to swell the membrane sufficiently. Then, free water on the surface of the ion exchange membrane was removed, and then the ion exchange membrane was weighed. Then, the ion exchange membrane was dried in a vacuum oven at 60°C for 24 hours, cooled, and then the ion exchange membrane was weighed. A water content ratio was determined by using the weighed amounts.

[113] WC(%) = {(W _wct - W _dry )/W _d[y } x 100

[114] WC: content of water ( ), W _wet : immersed weight (g), W^: dried weight (g)

[115] (3) Membrane Resistance

[116] A 2-compartment cell was used to measure an electric resistance of the ion exchange membrane. The membrane was cut to a specific size (3 3 cm), and incorporated in an electrochemical cell. Then, an electric resistance (R^ was measured in 0.1 M NaCl solution, and resistance (R ₂ ) of an electrolyte solution after removing the membrane was measured. Thereby, an electric resistance (ER) was determined.

[117] ER(Q-m ² ) = (R, - R ₂ ) x A

[118] R: resistance (Ω), A: area (m ² )

[119] (4) Solubility

[120] A crosslinked anionic membrane and a non-crosslinked anionic membrane were cut to a size of 5 x 5 cm, added into a dimethyl acetamide (DMAc) solvent, and then hold for 24 hours. Then, stability of the ion exchange membrane shape was observed by the naked eyes at room temperature. [Preparation Example 1]

Preparation of Active Layer-Formed Anode Electrode

1.5 mol of 4-vinylbenzenesulfonic acid sodium salt was dissolved in 50 mL of distilled water, 2 mol of methyl methacrylate, 0.5 mol of 4-chloromethyl styrene and 0.1 parts by weight of benzoyl peroxide were added thereto, reacted at 80°C for 24 hours, filtered to obtain a polymer powder (Mw = 181,913 Gel Permeation Chromatography: Model Waters 2690, solvent; Tetrahydrofuran (THF), polystyrene Mw = 7,000,000). The polymer powder was added to 500 ml of dimethyl formamide to prepare 20 wt of solution. Then, 0.25 mol of ethylene glycol was added to prepare a cation selective polymer matrix solution. 3.2 g of active carbon powder (P-60, manufactured by Daedong AC Co., specific surface area 1600m7g) was added in 40g of the cation selective polymer matrix solution to prepare a first composition.

The first composition thus prepared was applied by a Doctor blade so as to form a coating layer thickness of 200 #m on the side of respective conductive graphite sheets (thickness: 130 μχΆ, manufactured by Dongbang Carbon Co., Ltd., Cat. No. F02511C), and then dried at 70°C for 30 minutes to manufacture an electrode on which an active layer is formed.

[Preparation Example 2]

Preparation of Active Layer-Formed Cathode Electrode

0.5 mol of styrene, 1.5 mol of methyl methacrylate, 2.0 mol of 4-chloromethyl styrene, and 0.1 parts by weight of benzoyl peroxide were mixed, reacted at 80°C for 24 hours, filtered to obtain a polymer powder (Mw = 218,160 Gel Permeation Chromatography: Model Waters 2690, solvent; THF, polystyrene Mw = 7,000,000, see FIG. 6). The polymer powder was dissolved in 1 ,000 ml of dimethyl formamide, reacted with 1.5 mol of trimethyl amine at room temperature, followed by precipitation/preparation in methanol and vacuum drying at room temperature. After the vacuum drying, the resultant was added to 500 ml of dimethyl acetamide to prepare 20 wt% of solution. Then, 0.25 mol of ethylene glycol was added to prepare an anion selective polymer matrix solution. 3.2 g of active carbon powder (P-60, manufactured by Daedong AC Co., specific surface area 1600m7g) was added in 40g of the anion selective polymer matrix solution to prepare a first composition.

The first composition thus prepared was applied by a Doctor blade so as to form a coating layer thickness of 200 μχα on the side of respective conductive graphite sheets (thickness: 130 //m, manufactured by Dongbang Carbon Co., Ltd., Cat. No. F02511C), and then dried at 70°C for 30 minutes to manufacture an electrode on which an active layer is formed. [131] [Example 1]

[132] Preparation of electrode which is coated with cation selective resin and is

crosslinked bv thermal polymerization

[133] 1.5 mol of 4-vinylbenzenesulfonic acid sodium salt was dissolved in 50 mL of

distilled water, 2 mol of methyl methacrylate, 0.5 mol of 4-chloromethyl styrene and 0.1 parts by weight of benzoyl peroxide were added thereto, reacted at 80°C for 24 hours, filtered to obtain a polymer powder (Mw = 181,913 Gel Permeation Chromatography: Model Waters 2690, solvent; Tetrahydrofuran (THF), polystyrene Mw = 7,000,000). The polymer powder was added to 500 ml of dimethyl formamide to prepare 20 wt% of solution. Then, 0.25 mol of ethylene glycol was added to prepare a cation selective polymer matrix solution.

[134] The active layer prepared in Preparation Example 1 was dipped in the cation

selective polymer matrix solution thus prepared so as to form a coating layer thickness of 30 j an, and the resultant was crosslinked at 80°C for 1 hour to manufacture a negative electrode having a crosslinked cation selective layer.

[135]

[136] Preparation of electrode which is coated with anion selective resin and is

crosslinked by thermal polymerization

[137] 0.5 mol of styrene, 1.5 mol of methyl methacrylate, 2.0 mol of 4-chloromethyl

styrene, and 0.1 parts by weight of benzoyl peroxide were mixed, reacted at 80°C for 24 hours, filtered to obtain a polymer powder (Mw = 218,160 Gel Permeation Chromatography: Model Waters 2690, solvent; THF, polystyrene Mw = 7,000,000, see FIG. 6). The polymer powder was dissolved in 1,000 ml of dimethyl formamide, reacted with 1.5 mol of trimethyl amine at room temperature, followed by precipitation/preparation in methanol and vacuum drying at room temperature. At this time, synthesis of the prepared trimethyl ammonium chloride was confirmed with IR, and shown in FIG. 7. After the vacuum drying, the resultant was added to 500 ml of dimethyl acetamide to prepare 20 wt of solution. Then, 0.25 mol of ethylene glycol was added to prepare an anion selective polymer matrix solution.

[138] The active layer prepared in Preparation Example 2 was dipped in the anion selective polymer matrix solution thus prepared, so as to form a coating thickness of 25 pm, the resultant was crosslinked at 80°C for 1 hour to manufacture a positive electrode having a crosslinked anion selective layer.

[139]

[140] Deionization Efficiency Measurement of Crosslinked Ion Selective Capacitive Deionization Electrode

[141] The negative electrode and positive electrode having the crosslinked ion selective layer thus produced were used to manufacture a crosslink type deionization unit cell, and cut to a size of 10 x 10 cm2. The cell was equipped with a spacer (120 mesh, polyamide) having a thickness of 100 jam so as to pass through fluid while preventing contact between the positive electrode and the negative electrode. 1 cm of a hole was punched in the center of the electrode, solution was allowed to flow out to the center through the spacer from four sides of the electrode. Acryl plates having a size of 15 x 15 cm2 were placed on the outside of the positive electrode and negative electrode and fixed with bolts to manufacture a capacitive deionization unit cell.

[142] When an electrode potential of 1.5 V was applied constantly, 250 mg/L of NaCl solution was supplied in a flow rate of 30 mL/min. Conversion of Total dissolved solid (TDS) of outlet water was measured and then a deionization efficiency was measured. After adsorption for 3 minutes, deionization efficiency was determined in a manner to desorb ions while the electrode potential was changed to a short-circuit potential for 1 minute, a reversal potential for 50 seconds, and an idle state for 10 seconds. After deionization experiment was carried out by the prepared cell, TDS was measured and shown in FIG. 8. Salt removal rate (%) was shown in Table 1.

[143]

[144] [Example 2]

[145] Preparation of electrode which is coated with cation selective resin and is

crosslinked by UV photo-polymerization

[146] 1.5 mol of 4-vinylbenzenesulfonic acid sodium salt was dissolved in 50 niL of

distilled water, 2 mol of methyl mefhacrylate, 0.5 mol of hydroxyethyl acrylate and 0.1 parts by weight of benzophenone were added thereto, reacted at 80°C for 24 hours, to obtain a polymer powder (Mw = 181,913 Gel Permeation Chromatography: Model Waters 2690, solvent; Tetrahydrofuran (THF), polystyrene Mw = 7,000,000). The polymer powder was added to 500 ml of dimethyl formamide to prepare 20 wt of solution. Then, 0.25 mol of 4-chloromethyl styrene was added and reacted at 100°C for 4 hours to introduce a vinyl group, precipitated and cleaned in methanol, followed by vacuum drying at room temperature for 24 hours, 100 ml of dimethyl formamide was added to prepare 20 wt% of cation selective polymer matrix solution.

[147] The active layer prepared in Preparation Example 1 was dipped in the cation

selective polymer matrix solution thus prepared so as to form a coating layer thickness of 30 p , the resultant was crosslinked by an light radiation amount of UV light of 500 mJ/cm2 for 20 seconds to manufacture a negative electrode having a crosslinked cation selective layer

[148]

[149] Preparation of electrode which is coated with anion selective resin and is

crosslinked bv UV photo-polymerization

[150] 1.0 mol of styrene, 0.5 mol of hydroxyethyl acrylate, 1.5 mol of 4-chloromethyl styrene, and 0.1 parts by weight of benzophenone were mixed, reacted at 80°C for 24 hours, filtered to a polymer powder (Mw = 218,160 Gel Permeation Chromatography: Model Waters 2690, solvent; THF, polystyrene Mw = 7,000,000, see FIG. 6). The polymer powder was added to 500 ml of dimethyl formamide to prepare 20 wt of solution. Then, 0.25 mol of 4-chloromethyl styrene was added and reacted at 100°C for 4 hours, reacted with 1.5 mol of trimethyl amine at room temperature to introduce a vinyl group to the polymer matrix, precipitated and cleaned in methanol, followed by vacuum drying for 24 hours at room temperature, dissolved in 1000 ml of dimethyl formamide, reacted with 1.5 mol of trimethyl amine at room temperature, and precipitated and cleaned in methanol, followed by vacuum drying at room temperature. At this time, synthesis of the prepared trimethyl ammonium chloride was confirmed with IR, and shown in FIG. 7. After the vacuum drying, the resultant was added to 500 ml of dimethyl acetamide to prepare 20 wt% of solution.

[151] The active layer prepared in Preparation Example 2 was dipped in the anion selective polymer matrix solution thus prepared, so as to form a coating layer thickness of 25 m, and the resultant was crosslinked by an light radiation amount of UV light of 500 mJ/ cm2 for 20 seconds to manufacture a positive electrode having a crosslinked anion selective layer.

[152]

[153] Deionization Efficiency Measurement of Crosslinked Ion Selective Capacitive Deionization Electrode

[154] A negative electrode and a positive electrode having the crosslinked ion selective layer thus produced were used to manufacture a crosslink type deionization unit cell, and cut to a size of 10 x 10 cm2. The cell was equipped with a spacer (120 mesh, polyamide) having a thickness of 100 μτα so as to pass through fluid while preventing contact between the positive electrode and the negative electrode. 1 cm of a hole was punched in the center of the electrode, solution was allowed to flow out to the center through the spacer from four sides of the electrode. Acryl plates having a size of 15 x 15 cm2 were placed on the outside of the positive electrode and negative electrode and fixed with bolts to manufacture a capacitive deionization unit cell.

[155] When an electrode potential of 1.5 V was applied constantly, 250 mg L of NaCl solution was supplied in a flow rate of 30 mL/min. After deionization experiment was carried out by the prepared cell, salt removal rate (%) was shown in Table 1

[156]

[157] [Example 3]

[158] Crosslinked Cation Selective Membrane

[159] A cation selective membrane was prepared by casting the cation selective coating solution prepared in Example 1 on a Teflon plate in a constant amount (thickness 2 mm), followed by drying for 10 hours at 80°C.

[160]

[161] Crosslinked Anion Selective Membrane

[162] An anion selective membrane was prepared by casting the anion selective coating solution prepared in Example 1 on a Teflon plate in a constant amount (thickness 2 mm), followed by drying for 10 hours at 80°C.

[163]

[164] [Comparative Example 1]

[165] Preparation of Electrode Coated With Cation Selective Resin

[166] A cation selective coating solution was prepared by mixing 1.0 g of polystyrene (cation exchange capacity 1.5 meq/g) having a cation exchange group prepared through sulfonation reaction and 20 g of dimethyl acetamide (DMAc). The active layer prepared in Preparation Example 1 was dipped in the cation selective coating solution thus prepared to manufacture a negative electrode having a cation selective layer.

[167]

[168] Preparation of Electrode Coated With Anion Selective Resin

[169] An anion selective coating solution was prepared by mixing 1.0 g of

polyethersulfone (anion exchange capacity 1.2 meq/g) having an anion exchange group prepared through amination reaction and 20 g of dimethyl acetamide . The active layer prepared in Preparation Example 2 was dipped in the anion selective coating solution thus prepared to manufacture a positive electrode having an anion selective layer on the surface of the electrode.

[170]

[171] Deionization Efficiency Measurement of Non-Crosslinked Ion Selective Ca- pacitive Deionization Electrode

[172] A negative electrode and a positive electrode having the ion selective layer thus produced were used to manufacture a non-crosslink type deionization unit cell, cut to a size of 10 x 10 cm2. The cell was equipped with a spacer (120 mesh, polyamide) having a thickness of 100 pm so as to pass through fluid while preventing contact between the positive electrode and the negative electrode. 1 cm of a hole was punched in the center of the electrode, solution was allowed to flow out to the center through the spacer from four sides of the electrode. Acryl plates having a size of 15 x 15 cm2 were placed on the outside of the positive electrode and negative electrode and fixed with bolts to manufacture a capacitive deionization unit cell.

[173] When an electrode potential of 1.5 V was applied constantly, 250 mg/L of NaCl solution was supplied in a flow rate of 30 mL/min. Conversion of Total Dissolved Solid (TDS) of outlet water was measured and then a deionization efficiency was analyzed. After adsorption for 3 minutes, deionization efficiency was determined in a manner to desorb ions while the electrode potential was changed to a short-circuit potential for 1 minute, a reversal potential for 50 seconds, and an idle state for 10 seconds. After deionization experiment was carried out by the prepared cell, TDS was measured and shown in FIG. 8. Salt removal rate (%) was shown in Table 1.

[174]

[175] [Comparative Example 2]

[176] Non-Crosslinked Cation Selective Membrane

[177] A cation selective membrane was prepared by casting the cation selective coating solution prepared in Comparative Example 1 on a Teflon plate in a constant amount (thickness 2 mm), and then dried for 24 hours at 80°C.

[178]

[179] Non-Crosslinked Anion Selective Membrane

[180] An anion selective membrane was prepared by casting the anion selective coating solution prepared in Comparative Example 2 on a Teflon plate in a constant amount (thickness 2 mm), followed by drying for 24 hours at 80°C.

[181]

[182] [Table 1] Salt Removal Rate

[184] As shown in Table 1, it was known that the crosslinked ion selective capacitive deionization electrodes of Examples 1 and 2 have a salt removal rate higher than the non-crosslinked ion selective capacitive deionization electrode manufactured in Comparative Example 1.

[185] [Table 2] comparison of membrane properties

[186] Ion Water

Membrane

exchange content

esistance Solubil

Section r ity capacity ratio (DMAc) (meq/g) (Ω-cm ² )

(%)

Crosslinked

anionic

1.63 26 2 X membrane of

Example 1

Non- crosslinked

anionic

1.10 28 11

membrane of o Comparative

Example 1 [187] Further, as shown in Table 2, it was thought that the crosslinked anionic membrane of Examples 1 has a good ion selectivity because it has a low water content ratio despite a high ion exchange capacity, further an ion conductivity may be improved due to lower electric resistance of a coating layer, and therefore a salt removal rate may be improved.

[188] FIG, 7 is a result obtained by analyzing the anion selective polymer matrix solution prepared in Examples 1 and 2 with IR. Synthesis of an anion selective trimethyl ammonium chloride obtained by reacting the prepared polymer powder with trimethyl amine was confirmed with IR. With respect to the measured IR data, synthesis of the anion selective resin was confirmed through an absorption peak due to stretching vibration (C=0) at 1722 cnr ¹ because of a large amount of MMA, a -CH3 absorption peak in wavelength band of 1470 to 1375 cm ¹ , an absorption peak due to C-H vibration of trimethyl amine at a wavelength of 2980 cm-1 and C-N absorption peak at 1339 cm ¹ .

[189] As shown in FIG. 8, a result obtained after deionization experiment was performed using the crosslinked ion selective capacitive deionization electrode of Example 1 and the non-crosslinked ion selective capacitive deionization electrode of Comparative Example 1, is shown as Total Dissolved Solid (TDS) curve. It was known that the crosslinked ion selective capacitive deionization electrode of Example 1 has a lower value and a better deionization efficiency than the non-crosslinked ion selective capacitive deionization electrode of Comparative Example 1.

[190] FIG. 9 is a result of observing a scanning electronic microscope image in order to confirm a variation of a coating layer on the surface of the electrode, after the crosslinked ion selective capacitive deionization electrode (a) and the non-crosslinked ion selective capacitive deionization electrode (b) is subjected to adsorption and desorption experiments in a 100 ppm solution of NaCl solution in a flow rate of 70 ml/ min at 80°C for one month. It was confirmed that, a shape of a coating layer of the crossrinked ion selective capacitive deionization electrode is maintained, while a coating layer of a non-crosslinked ion selective capacitive deionization electrode is almost lost. Therefore, when the electrode was coated with the ion selective resin to manufacture an ion selective capacitive deionization electrode, it could be confirmed that the crosslinked ion selective capacitive deionization electrode has a higher durability and a better salt removal efficiency than a non-crosslinked ion selective capacitive deionization electrode.