JP6066804B2 - Organic wastewater treatment method - Google Patents

Description

  In the present invention, when waste water containing salts and organic matter (TOC) discharged from an electronic device manufacturing factory or the like is treated using an electrodialyzer, the voltage rise due to the film surface adhesion of the organic matter in the electrodialyzer is reduced. The present invention relates to a method for treating organic wastewater that can prevent and efficiently remove salts stably over a long period of time.

  In recent years, environmental standards and water quality standards tend to be stricter, and it is desired to purify discharged water to a high degree. On the other hand, for the purpose of eliminating water shortage, development of advanced water treatment technology is also desired in order to collect and reuse various wastewater.

  In Patent Document 1, when waste water containing high-concentration TOC or low-concentration TOC containing acetone, isopropyl alcohol, etc. discharged from the semiconductor manufacturing process is recovered and reused, this is first biologically treated to remove the TOC component. A method for purifying biologically treated water by reverse osmosis (RO) membrane treatment is disclosed.

  Patent Document 2 adds to the organic matter-containing wastewater an organic matter-containing wastewater with a scale inhibitor more than 5 times the weight of calcium ions in the organic matter-containing wastewater, and before, after, or simultaneously with the addition of the scale inhibitor. A method and apparatus for adjusting the pH to 9.5 or higher and then performing RO separation treatment is disclosed.

  Patent Document 3 discloses a scale inhibitor addition step for adding a scale inhibitor to organic matter-containing wastewater, and an organic matter-containing wastewater to which the scale inhibitor has been added is supplied to a reverse osmosis membrane separation device. In the method for treating organic matter-containing wastewater, the method comprises: a reverse osmosis membrane separation step for separating the organic matter-containing wastewater, and a pH adjustment step for adjusting the pH of the organic matter-containing wastewater supplied to the reverse osmosis membrane separation device to 9.5 or more In addition, a method for treating organic matter-containing wastewater is disclosed, in which a sulfur compound containing a peroxide group is added and ultraviolet rays are irradiated to oxidize the concentrated water.

  In electrodialysis, a cation exchange membrane and an anion exchange membrane are alternately arranged between an anion and a positive electrode, and a salt is placed in the desalination chamber in an electrodialysis tank comprising a desalination chamber and a concentration chamber. In this method, a direct current voltage is applied between the two electrodes while flowing an organic solution containing a solution containing an electrolyte in the concentrating chamber, for example, a diluted saline solution. As a result, salts (ash) present in the organic solution permeate through the ion exchange membrane as ions and move to the concentration side to be desalted. A method of desalting salts contained in organic substances in such an ion exchange membrane electrodialysis tank is effective.

  Patent Document 4 is selected from the group consisting of biological treatment, coagulation sedimentation treatment, sand filtration treatment, and microfiltration membrane treatment after performing softening treatment to reduce calcium concentration on organic wastewater containing salts and organic matter. A pretreatment step for performing SS removal treatment comprising one or more treatments or a combination of two or more, an electrodialysis treatment step for separating electrodialyzed concentrated water and electrodialyzed water by electrodialysis treatment, and reverse osmosis membrane treatment In an organic wastewater treatment method comprising a reverse osmosis membrane treatment step that separates reverse osmosis concentrate and reverse osmosis membrane treatment water, the electrodialysis concentrate obtained from the electrodialysis treatment step is supplied to an electrolytic treatment apparatus. An organic wastewater treatment method is disclosed in which electrolysis is performed to produce a sodium hypochlorite solution.

JP 2002-336886 A JP 2005-169372 A JP 2007-244930 A JP 2012-130891 A

  According to the method disclosed in Patent Document 1, when biological wastewater is passed through an RO membrane separation device, the membrane surface of the RO membrane is blocked by biological metabolites generated by the decomposition of organic matter by microorganisms, and the flux decreases. There was a problem. In addition, the wastewater discharged from the electronic device manufacturing factory may be mixed with a nonionic surfactant that may adhere to the membrane surface of the RO membrane separator and reduce the flux. However, there has been a problem that RO membrane separation treatment cannot be applied to such nonionic surfactant-containing wastewater.

  Addition of the expensive slime control agent and scale inhibitor disclosed in Patent Document 2 or 3 causes an increase in processing cost, and therefore a cheaper method is required.

  The electrodialysis method disclosed in Patent Document 4 is an electrodialysis in which a cation exchange membrane and an anion exchange membrane are alternately arranged between an anion and a positive electrode to constitute a desalination chamber and a concentration chamber. In this method, a direct current voltage is applied between the two electrodes while circulating a solution of an organic substance containing salts in a desalting chamber and a solution containing an electrolyte such as dilute saline in a concentration chamber. As a result, salts (ash) present in the organic solution permeate through the ion exchange membrane as ions and move to the concentration side to be desalted. A method of desalting salts contained in organic substances in such an ion exchange membrane electrodialysis tank is effective. However, there is a problem that the organic matter adheres to the surface of the ion exchange membrane during electrodialysis, but Patent Document 4 does not disclose a countermeasure for preventing organic matter contamination.

  Accordingly, an object of the present invention is to obtain an ion exchange membrane having excellent resistance to organic contamination when performing an electrodialysis treatment on an organic wastewater containing salts and organic substances, and performing electrodialysis using the ion exchange membrane. That is, it is to provide a method for treating organic waste water by performing electrodialysis using such an ion exchange membrane having excellent resistance to organic contamination.

  As a result of intensive studies to solve the above problems, the present inventors have found that a microphase in a cation exchange membrane comprising an anionic polymer segment having an anionic group and a vinyl alcohol copolymer having a vinyl alcohol polymer segment. Separation is affected by the content of salts mixed as impurities in the vinyl alcohol copolymer, and by forming a film by reducing the content of salts, the domain size is reduced, and microphase separation is suppressed, As a result, it has excellent electrical characteristics such as charge density and membrane resistance. Furthermore, by making it more hydrophilic than conventional ion exchange membranes such as styrenedivinylbenzene, it can provide organic contamination resistance with almost no increase in membrane resistance. The present inventors have found that this can be done and have completed the present invention.

That is, the present invention performs an SS removal treatment on an organic wastewater containing salts and organic matter, and then performs an electrodialysis treatment on the organic wastewater after the SS removal treatment to obtain an electrodialysis concentrated water and an electrodialysis. In the method of treating organic wastewater separated into treated water,
As a cation exchange membrane in the electrodialysis treatment,
A microphase-separated structure comprising an anionic polymer segment having an anionic group and a vinyl alcohol copolymer having a vinyl alcohol polymer segment and having a domain size (X) in the range of 0 nm <X ≦ 150 nm. An organic wastewater treatment method characterized by using a cation exchange membrane.
In the present invention, microphase separation means that in a copolymer containing two or more types of chain polymers, the same kind of polymer segments aggregate together and a repulsive interaction acts between different polymer segments. A periodic structure obtained by forming a periodic self-organized structure from nanoscale to submicron scale. In the present invention, the domain means a mass formed by aggregating polymer segments of the same kind in one or a plurality of polymer chains.

  The nil alcohol polymer segment is a segment formed from a vinyl alcohol polymer not containing an anionic group, and electrodialysis treatment is performed using a cation exchange membrane containing a vinyl alcohol copolymer having the segment. Preferably it is done.

  It is preferable that a cross-linked structure is introduced into the vinyl alcohol copolymer.

  The vinyl alcohol copolymer is preferably an anionic block copolymer having a vinyl alcohol polymer block and an anionic polymer block having an anionic group.

  The vinyl alcohol copolymer is preferably an anionic graft copolymer having a vinyl alcohol polymer block and an anionic polymer block having an anionic group.

  The SS treatment is preferably composed of one or more treatments or a combination of two or more selected from the group consisting of biological treatment for organic wastewater, coagulation sedimentation treatment, sand filtration treatment, and microfiltration membrane treatment.

  According to the organic wastewater treatment method of the present invention, the cation exchange membrane used for the electrodialysis treatment is composed of a vinyl alcohol copolymer having an anionic polymer segment and a vinyl alcohol polymer segment. However, since the ion exchange membrane is formed by reducing the content of salts contained as impurities in the vinyl alcohol copolymer, the microphase of the anionic polymer segment and the vinyl alcohol polymer segment is formed. Separation is suppressed, and a film having a domain size larger than 0 nm and 150 nm or less is formed. For this reason, as the cation exchange membrane, since the vinyl alcohol polymer segment has high hydrophilicity, the membrane resistance is low, and the microphase separation is suppressed as described above, so that the ion path structure is densely formed and durable. The electrodialysis can be performed stably and efficiently over a long period of time. By performing electrodialysis treatment of organic wastewater using such a cation exchange membrane, the cation exchange membrane can be stably electrodialyzed over a long period of time while maintaining low electrical resistance without organic contamination. It is possible to efficiently treat organic wastewater

It is a transmission electron microscope (TEM) photograph of the ion exchange membrane (CEM-5) used in Example 5, which is an example of a cation exchange membrane used in the method of the present invention. It is a TEM photograph of the ion exchange membrane (CEM-7) used in Example 7, which is an example of a cation exchange membrane used in the method of the present invention. 4 is a TEM photograph of an ion exchange membrane (CEM-8) used in Comparative Example 1. 4 is a TEM photograph of an ion exchange membrane (CEM-9) used in Comparative Example 2. 10 is a TEM photograph of an ion exchange membrane (CEM-10) used in Comparative Example 3. It is explanatory drawing of the apparatus used for the measurement of the membrane resistance of the cation exchange membrane of this invention. It is the schematic which shows an example of the apparatus used for the processing method of the organic wastewater of this invention. It is the schematic which shows the organic wastewater treatment apparatus used in the comparative example 6.

(Treatment of organic wastewater by electrodialysis)
In the present invention, after performing SS removal treatment on organic wastewater containing salts and organic matter, electrodialysis treatment is performed on the organic wastewater after the SS removal treatment, and electrodialyzed concentrated water and electrodialysis treated water. It is related with the processing method of the organic waste water isolate | separated into. In the present invention, electrodialysis refers to an electrodialysis tank constructed by alternately arranging a plurality of cation exchange membranes (cathode side) and anion exchange membranes (anode side) between an anode and a cathode. By supplying organic wastewater and energizing it,
Although it means the operation of separating into electrodialyzed concentrated water and electrodialyzed water, the feature of the present invention is that as a cation exchange membrane in the electrodialyzed process,
A microphase-separated structure comprising an anionic polymer segment having an anionic group and a vinyl alcohol copolymer having a vinyl alcohol polymer segment and having a domain size (X) in the range of 0 nm <X ≦ 150 nm. The cation exchange membrane is used.
Therefore, the cation exchange membrane used in the present invention will be described in detail below.

(Cation exchange membrane)
The cation exchange membrane used in the present invention is composed of an anionic polymer segment having an anionic group and a vinyl alcohol copolymer having a vinyl alcohol polymer segment. Usually, an anionic polymer segment and a vinyl alcohol polymer segment are bonded by a covalent bond to constitute a vinyl alcohol copolymer. In the present invention, the polymer segment means a polymer chain containing the same repeating unit in which two or more of the same monomer units are linked, and is a polymer block in a block copolymer, a trunk chain or a branch in a graft polymer. It is used as a term encompassing polymer blocks corresponding to chains. Further, in the anionic polymer segment having an anionic group, the anionic group may be contained at the end of the polymer, and therefore the monomer having the anionic group may not be a repeating unit.
As described above, the cation exchange membrane used in the present invention is composed of an anionic polymer segment having an anionic group and a vinyl alcohol copolymer having a vinyl alcohol polymer segment. In addition to this copolymer, a phase separation of a vinyl alcohol polymer that does not have an anionic group that is not bonded to an anionic polymer segment, and an anionic polymer that is not bonded to a vinyl alcohol polymer. It may be included to the extent that it does not affect the structure.

  The cation exchange membrane used in the present invention is formed by reducing the content of salts contained in the vinyl alcohol copolymer, so that the vinyl alcohol copolymer constituting the membrane exhibits a microphase separation structure. The inventors have found that the domain size can be made 150 nm or less. The cation exchange membrane used in the present invention is usually provided for practical use by crosslinking the vinyl alcohol polymer segment, but the domain size (X) is specified in the range of 0 nm <X ≦ 150 nm, It is possible to obtain a cation exchange membrane useful for electrodialysis having no change in ion path structure, stable membrane structure, and excellent electrical characteristics such as charge density and membrane resistance. The domain size (X) becomes smaller as the salt content is lowered, and can be set to 0 nm <X ≦ 130 nm, and further 0 nm <X ≦ 100 nm.

  The cation exchange membrane used in the present invention is a hydrophilic ion exchange membrane because it is composed of a vinyl alcohol copolymer having a vinyl alcohol polymer segment as described above. This has the advantage that contamination due to adhesion of organic pollutants in the liquid to be treated can be suppressed. Here, that the constituent polymer is hydrophilic means that the polymer has hydrophilicity in a structure having no functional group (anionic group) necessary for the anionic polymer. As described above, since the constituent polymer is a hydrophilic polymer, a cation exchange membrane having a high degree of hydrophilicity is obtained, and organic contaminants in the liquid to be treated adhere to the cation exchange membrane and the performance of the membrane. The problem of lowering can be reduced. Moreover, it has the advantage that film | membrane intensity | strength becomes high.

(Anionic polymer)
The anionic polymer constituting the anionic polymer segment used in the present invention is a polymer containing an anionic group in the molecular chain. The anionic group may be contained in any of the main chain, side chain, and terminal. Examples of the anionic group include a sulfonate group, a carboxylate group, and a phosphonate group. In addition, functional groups that can be converted into sulfonate groups, carboxylate groups, and phosphonate groups at least partially in water, such as sulfonic acid groups, carboxyl groups, and phosphonic acid groups are also included in the anionic groups. Of these, a sulfonate group is preferred because of its large ion dissociation constant. The anionic polymer may contain only one type of anionic group or may contain a plurality of types of anionic groups. Moreover, the counter cation of an anionic group is not specifically limited, A hydrogen ion, an alkali metal ion, etc. are illustrated. Of these, alkali metal ions are preferred from the viewpoint of less equipment corrosion problems. The anionic polymer may contain only one type of counter cation or may contain a plurality of types of counter cation.

  The anionic polymer used in the present invention may be a polymer composed only of a structural unit containing the anionic group, or may be a polymer further containing a structural unit not containing the anionic group. Good. Moreover, it is preferable that these polymers have a crosslinking property. An anionic polymer may consist of only one type of polymer, or may include a plurality of types of anionic polymers. Moreover, you may be a mixture of these anionic polymers and another polymer. Here, the polymer other than the anionic polymer is preferably not a cationic polymer.

  As an anionic polymer, what has the structural unit of the following general formula (1) and (2) is illustrated.

［式中、Ｒ^５は水素原子またはメチル基を表す。Ｇは−ＳＯ_３Ｈ、−ＳＯ_３−Ｍ^＋、−ＰＯ_３Ｈ、−ＰＯ_３−Ｍ^＋、−ＣＯ_２Ｈまたは−ＣＯ_２−Ｍ^＋を表す。Ｍ^＋はアンモニウムイオンまたはアルカリ金属イオンを表す。］

[Wherein R ⁵ represents a hydrogen atom or a methyl group. G represents _{^{-SO 3 H, -SO 3 -M +}} , -PO 3 H, -PO 3 -M +, a -CO ₂ H or _-CO 2 -M ^+. M ⁺ represents an ammonium ion or an alkali metal ion. ]

  Examples of the anionic polymer containing the structural unit represented by the general formula (1) include 2-acrylamido-2-methylpropanesulfonic acid homopolymer or copolymer.

［式中、Ｒ５は水素原子またはメチル基を表わし、Ｔは水素原子がメチル基で置換されていてもよいフェニレン基またはナフチレン基を表わす。Ｇは一般式（１）と同義である。］

[Wherein, R5 represents a hydrogen atom or a methyl group, and T represents a phenylene group or a naphthylene group in which the hydrogen atom may be substituted with a methyl group. G is synonymous with the general formula (1). ]

  Examples of the anionic polymer containing the structural unit represented by the general formula (2) include homopolymers or copolymers of p-styrene sulfonate such as sodium p-styrene sulfonate.

  Examples of the anionic polymer include homopolymers or copolymers of sulfonic acids such as vinyl sulfonic acid and (meth) allyl sulfonic acid or salts thereof, fumaric acid, maleic acid, itaconic acid, maleic anhydride, itaconic anhydride. Examples include dicarboxylic acids such as acids, homopolymers or copolymers of derivatives or salts thereof.

In the general formula (1) or (2), G is preferably a sulfonate group, a sulfonic acid group, a phosphonate group, or a phosphonic acid group that gives a higher charge density. In the general formulas (1) and (2), examples of the alkali metal ion represented by M ⁺ include sodium ion, potassium ion, and lithium ion.

(Vinyl alcohol polymer segment)
In the present invention, as the polyvinyl alcohol constituting the vinyl alcohol polymer segment, a vinyl ester polymer obtained by polymerizing a vinyl ester monomer is saponified and the vinyl ester unit is used as a vinyl alcohol unit. . Examples of the vinyl ester monomers include vinyl formate, vinyl acetate, vinyl propionate, vinyl valelate, vinyl laurate, vinyl stearate, vinyl benzoate, vinyl pivalate, vinyl versatate, and the like. Of these, vinyl acetate is preferably used.
When the vinyl ester monomer is copolymerized, a monomer that can be copolymerized, if necessary, within a range that does not impair the effects of the invention (preferably 50 mol% or less, more preferably 30 mol% or less). It may be copolymerized.
Examples of the monomer copolymerizable with the vinyl ester monomer include olefins having 3 to 30 carbon atoms such as ethylene, propylene, 1-butene and isobutene; acrylic acid and salts thereof; methyl acrylate and acrylic acid. Ethyl, n-propyl acrylate, i-propyl acrylate, n-butyl acrylate, i-butyl acrylate, t-acrylate
Acrylic esters such as butyl, 2-ethylhexyl acrylate, octadecyl acrylate; methacrylic acid and its salts; methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, i-propyl methacrylate, methacryl Methacrylic acid esters such as n-butyl acid, i-butyl methacrylate, t-butyl methacrylate, 2-ethylhexyl methacrylate, dodecyl methacrylate, octadecyl methacrylate;
Acrylamide derivatives such as acrylamide, N-methyl acrylamide, N-ethyl acrylamide, N, N-dimethyl acrylamide, diacetone acrylamide, acrylamide propane sulfonic acid and its salt, acrylamide propyl dimethylamine and its salt, N-methylol acrylamide and its derivative Methacrylamide derivatives such as methacrylamide, N-methylmethacrylamide, N-ethylmethacrylamide, methacrylamidepropanesulfonic acid and its salts, methacrylamidepropyldimethylamine and its salts, N-methylolmethacrylamide and its derivatives; N-vinylamides such as vinylformamide, N-vinylacetamide, N-vinylpyrrolidone; methyl vinyl ether, ethyl vinyl Ether, n- propyl vinyl ether, i- propyl vinyl ether, n- butyl vinyl ether, i- butyl vinyl ether, t- butyl ether, dodecyl vinyl ether and stearyl vinyl ether;
Nitriles such as acrylonitrile and methacrylonitrile; vinyl chloride, vinylidene chloride,
Vinyl halides such as vinyl fluoride and vinylidene fluoride; allyl compounds such as allyl acetate and allyl chloride; maleic acid and its salts or esters thereof; itaconic acid and its salts or esters thereof; vinylsilyl compounds such as vinyltrimethoxysilane And isopropenyl acetate.

  The structural units other than the anionic group in the vinyl alcohol copolymer can be selected independently, but the copolymer is preferably composed of monomers having the same structural unit. . Thereby, since the affinity between domains becomes high, the mechanical strength of a cation exchange membrane increases. The vinyl alcohol copolymer preferably has 50 mol% or more of the same structural unit, more preferably 70 mol% or more.

Moreover, since it is desirable that it is hydrophilic, it is particularly preferable that the same structural unit is a vinyl alcohol unit. By having a vinyl alcohol unit, the domains can be chemically crosslinked with a crosslinking agent such as glutaraldehyde, so that the mechanical strength of the cation exchange membrane can be further increased.

As described above, in the present invention, the vinyl alcohol copolymer having an anionic polymer segment and a vinyl alcohol polymer segment has a structure in which the anionic polymer segment and the vinyl alcohol polymer segment are bonded. preferable.

  The cation exchange membrane used in the present invention is composed of a vinyl alcohol copolymer having a vinyl alcohol polymer segment in the anionic polymer segment as described above. The vinyl alcohol copolymer is anionic. It may be composed of a mixture including a vinyl alcohol polymer containing no group.

(Block or graft copolymer)
In the present invention, the vinyl alcohol copolymer is preferably such that the anionic polymer segment and the vinyl alcohol polymer segment form a block copolymer or a graft copolymer. Among these, a block copolymer is more preferably used. By doing this, the vinyl alcohol polymer block responsible for the function of improving the strength of the entire cation exchange membrane, suppressing the degree of swelling of the membrane, and maintaining the shape, and the amount of anionic group responsible for the permeation of the cation The anionic polymer block formed by polymerizing the polymer can share the role, and both the ion permeation function and the dimensional stability of the cation exchange membrane can be achieved. The structural unit of the polymer block obtained by polymerizing the anionic group monomer is not particularly limited, and examples thereof include those represented by the general formulas (1) to (2). Among these, from the viewpoint of easy availability, as the monomer constituting the anionic polymer, p-styrene sulfonate or 2-acrylamido-2-methylpropane sulfonate is used. Anionic block copolymer containing an anionic polymer block obtained by polymerizing an acid salt and a vinyl alcohol polymer block, or an anionic polymer obtained by polymerizing 2-acrylamido-2-methylpropanesulfonate A block copolymer comprising a block and a vinyl alcohol polymer block is preferably used.
The graft copolymer includes an anionic polymer segment as a backbone and a vinyl alcohol polymer segment as a branched chain, and a vinyl alcohol polymer segment as a backbone and an anionic polymer segment as a branch. Sometimes it is a chain. Although not particularly limited in the present invention, from the viewpoint of easily obtaining strength properties, vinyl alcohol as a backbone,
A graft copolymer having an anionic polymer segment as a branched chain is preferred. A known method is applied as the graft copolymerization method.

(Method for producing block copolymer)
The method for producing a block copolymer containing an anionic polymer block obtained by polymerizing an anionic monomer used in the present invention and a vinyl alcohol polymer block is mainly classified into the following two methods. . (1) a method in which a desired block copolymer is produced and then an anionic group is bonded to a specific block; and (2) at least one anionic group monomer is polymerized to form a desired block copolymer. It is a method for producing a polymer. Among these, for (1), one or more types of monomers are block copolymerized in the presence of polyvinyl alcohol having a mercapto group at the terminal, and then one or more types of polymer in the block copolymer are copolymerized. For the method of introducing an ionic group into the coalescing component, (2), a block copolymer is produced by radical polymerization of at least one anionic group monomer in the presence of polyvinyl alcohol having a mercapto group at the terminal. However, these methods are preferable because of industrial ease. In particular, the type and amount of constituent monomers in each block of an anionic polymer block obtained by polymerizing a vinyl alcohol block and an anionic group monomer in the block copolymer can be easily controlled. A method of producing a block copolymer by radical polymerization of at least one anionic group monomer in the presence of a group-containing polyvinyl alcohol is preferred. The block copolymer containing a polymer block obtained by polymerizing the anionic group monomer thus obtained and a vinyl alcohol polymer block contains unreacted polyvinyl alcohol having a mercapto group at the terminal. It doesn't matter.

The vinyl alcohol polymer having a mercapto group at the end used for the production of these block copolymers can be obtained, for example, by the method described in JP-A-59-187003. That is, a vinyl ester monomer in the presence of thiolic acid,
For example, a method of saponifying a vinyl ester polymer obtained by radical polymerization of vinyl acetate can be mentioned. A method for obtaining a block copolymer using a polyvinyl alcohol having a mercapto group at the terminal thus obtained and an anionic group monomer is described in, for example, JP-A-59-189113. Method. That is, a block copolymer can be obtained by radical polymerization of an anionic group monomer in the presence of polyvinyl alcohol having a mercapto group at the terminal. This radical polymerization can be carried out by a known method such as bulk polymerization, solution polymerization, pearl polymerization, emulsion polymerization, etc., but mainly contains a solvent capable of dissolving polyvinyl alcohol containing a mercapto group at the terminal, such as water or dimethyl sulfoxide. It is preferable to carry out in the medium. As the polymerization process, any of a batch method, a semi-batch method, and a continuous method can be employed.

The above radical polymerization may be performed by using a normal radical polymerization initiator such as 2,2′-azobisisobutyronitrile, benzoyl peroxide, lauroyl peroxide, diisopropyl peroxycarbonate, 4,4′-azobis- (4-cyano Pentanoic sodium), 4,4'-azobis- (4-cyanopentanoic ammonium), 4,4'-azobis- (4-cyanopentanoic potassium), 4,4'-azobis- (4- Cyanopentanoic lithium), 2,2'-azobis {2-methyl-N- [1,1'-bis (hydroxymethyl) -2-hydroxyethyl] propionamide}, potassium persulfate, ammonium persulfate, etc. Can be used by using one that is suitable for the polymerization system, but in the case of polymerization in an aqueous system, vinyl alcohol Initiation of redox by a mercapto group at the end of a polymer and an oxidizing agent such as potassium bromate, potassium persulfate, ammonium persulfate, hydrogen peroxide, 2'-
Azobis [2-methyl-N (2-hydroxyethyl) propionamide] and the like are also possible. In particular, those that do not generate ionic residues after decomposition are particularly preferred.

As a catalyst for the saponification reaction of a vinyl ester polymer, an alkaline substance is usually used.
Examples thereof include alkali metal hydroxides such as potassium hydroxide and sodium hydroxide, and alkali metal alkoxides such as sodium methoxide. The saponification catalyst is
It may be added all at once at the beginning of the saponification reaction, or a part thereof may be added at the beginning of the saponification reaction, and the rest may be added during the saponification reaction. Examples of the solvent used for the saponification reaction include methanol, methyl acetate, dimethyl sulfoxide, diethyl sulfoxide, dimethylformamide and the like. Of these solvents, methanol is preferred. The saponification reaction can be carried out by either a batch method or a continuous method. After completion of the saponification reaction, the remaining saponification catalyst may be neutralized as necessary, and usable neutralizing agents include organic acids such as acetic acid and lactic acid, and ester compounds such as methyl acetate. .

(Degree of saponification of vinyl alcohol polymer)
Although the saponification degree of a vinyl alcohol polymer is not specifically limited, It is preferable that it is 40-99.9 mol%. If the degree of saponification is less than 40 mol%, the crystallinity is lowered and the strength of the cation exchange membrane may be insufficient. More preferably, the saponification degree is 60 mol% or more, and 8
More preferably, it is 0 mol% or more. Usually, the saponification degree is 99.9 mol% or less. At this time, the saponification degree when the polyvinyl alcohol is a mixture of plural kinds of polyvinyl alcohols refers to the average saponification degree of the whole mixture. The saponification degree of polyvinyl alcohol is a value measured according to JIS K6726.

(Polyvinyl alcohol polymerization degree)
The viscosity average degree of polymerization of the polyvinyl alcohol constituting the vinyl alcohol polymer segment (hereinafter sometimes simply referred to as the degree of polymerization) is not particularly limited, but is preferably 50 to 10,000. When the degree of polymerization is less than 50, there is a possibility that the cation exchange membrane cannot maintain sufficient strength in practical use. More preferably, the degree of polymerization is 100 or more. The degree of polymerization is 10,000
If it exceeds 1, the viscosity of the polymer aqueous solution will be too high, it will be difficult to apply, and the resulting film may be prone to defects. The degree of polymerization is more preferably 8000 or less. At this time,
The degree of polymerization when the polyvinyl alcohol is a mixture of a plurality of types of polyvinyl alcohol refers to the average degree of polymerization of the entire mixture. In addition, the viscosity average polymerization degree of polyvinyl alcohol is a value measured according to JIS K6726. The polymerization degree of polyvinyl alcohol containing no ionic group used in the present invention is also preferably within the above range.

(Content of anionic group monomer unit)
The content of the anionic group monomer unit in the vinyl alcohol copolymer constituting the cation exchange membrane is not particularly limited, but the content of the anionic group monomer unit of the copolymer, that is, the above The ratio of the number of anionic group monomer units to the total number of monomer units in the copolymer is preferably 0.1 mol% or more. When the content of the anionic group monomer unit is less than 0.1 mol%, the effective charge density in the cation exchange membrane is lowered, and the electrolyte permselectivity may be lowered. The content of the anionic group monomer unit is more preferably 0.5 mol% or more, and further preferably 1 mol% or more. Moreover, it is preferable that content of an anionic group monomer unit is 50 mol% or less. When the content of the anionic group monomer unit exceeds 50 mol%, the degree of swelling of the cation exchange membrane increases, the effective charge density in the cation exchange membrane decreases, and the electrolyte permselectivity may decrease. There is. The content of the anionic group monomer unit is more preferably 30 mol% or less, and further preferably 20 mol% or less. When the vinyl alcohol copolymer is a mixture of a polymer containing an anionic group and a polymer containing no anionic group, or a mixture of a plurality of polymers containing an anionic group The content of anionic group monomer units refers to the ratio of the number of anionic group monomer units to the total number of monomer units in the mixture.

(Method for producing cation exchange membrane)
A feature of the method for producing a cation exchange membrane used in the present invention is that a vinyl alcohol polymer segment and a vinyl alcohol copolymer (preferably a block copolymer) having an anionic polymer segment having an anionic group as constituent components. The phase separation domain size is reduced by forming a film by reducing the salt in the copolymer and forming a film. The salts referred to herein have an anionic group that constitutes an anionic polymer segment having an anionic group, such as sulfate and acetate which are impurities contained in the polyvinyl alcohol constituting the vinyl alcohol polymer segment. Examples thereof include metal salts such as bromide salts, chloride salts, nitrates, and phosphates contained as impurities in the monomer. These salts are inevitably mixed as impurities in the vinyl alcohol copolymer, and the present inventors have mixed the impurities into the anionic heavy weight in the vinyl alcohol copolymer during film formation. It has been found that the microphase separation of the coalesced segment is increased to adversely affect the membrane characteristics. In the present invention, the phase separation domain size of the membrane can be reduced by reducing the content of salts contained in the vinyl alcohol copolymer to form a membrane. At this time, the ratio (weight ratio) (C) / (P) of the weight (C) of the salt to the weight (P) of the vinyl alcohol copolymer is required to be 4.5 / 95.5 or less. In order to reduce the separation domain size, it is 4.0 / 96.0 or less, more preferably, 3.5 / 96.5 or less, and the weight ratio (C) / (P) is 4.5 / 95.5. If it exceeds 1, the microphase separation domain size of the anionic group polymer segment will increase, and when used as a cation exchange membrane, the ion path structure will change, and a durable cation exchange membrane cannot be obtained. .

Although there is no particular limitation on reducing the salt content contained in the vinyl alcohol copolymer to a predetermined value or less, for example, for impurities contained in polyvinyl alcohol constituting the vinyl alcohol polymer segment, polymer flakes may be used. Can be reduced by washing with water.
In addition, impurities contained in the polymer constituting the anionic polymer segment can be reduced by reprecipitation purification in a poor solvent of a polymer solution obtained by dissolving the polymer in an appropriate solvent, thereby purifying the polymer. Can do.
In the present invention, the salt content only needs to be reduced as described above. Therefore, one or both of polyvinyl alcohol and anionic polymer are purified to reduce the content to the above-described content. Just do it.

(Film formation)
The vinyl alcohol copolymer having a salt content adjusted as described above is dissolved in a solvent composed of water, a lower alcohol such as methanol, ethanol, 1-propanol, 2-propanol, or a mixed solvent thereof, A film having a predetermined thickness can be formed by extruding from a die, forming into a film, and removing the solvent by volatilization. The film forming temperature when the film is formed on a plate or a roller is not particularly limited, but a temperature range of about room temperature to about 100 ° C. is usually appropriate. Solvent removal can be performed by heating as appropriate.

(Film thickness)
The cation exchange membrane used in the present invention preferably has a thickness of about 30 to 1000 μm from the viewpoints of performance, mechanical strength, handling properties, etc. required as an electrolyte membrane for electrodialysis. When the film thickness is less than 30 μm, the mechanical strength of the film tends to be insufficient. On the other hand, when the film thickness exceeds 1000 μm, the membrane resistance increases and sufficient ion exchange properties are not exhibited, so that the electrodialysis efficiency tends to decrease. Preferably it is 40-500 micrometers, More preferably, it is 50-300 micrometers.

(Crosslinking treatment)
The cation exchange membrane used in the present invention is preferably subjected to a crosslinking treatment after film formation. By performing the crosslinking treatment, the mechanical strength of the resulting cation exchange membrane is increased. The method for the crosslinking treatment is not particularly limited, and may be a method of chemically bonding the molecular chains of the polymer or introducing physical bonds by heat treatment or the like.

When chemically bonding, a method of immersing in a solution containing a crosslinking agent is usually used. Examples of the crosslinking agent include polyvinyl alcohol acetalizing agents such as glutaraldehyde, formaldehyde, and glyoxal. Among them, dialdehyde crosslinking agents such as glutaraldehyde and gliogital are preferable. The concentration of the crosslinking agent is usually 0.001 to 10% by volume of the crosslinking agent relative to the solution. The crosslinking reaction can be performed by treating the polyvinyl alcohol copolymer with the above aldehyde in water, alcohol or a mixed solvent thereof under acidic conditions to chemically introduce a crosslinking bond. . After the crosslinking reaction, it is preferable to remove unreacted aldehyde, acid and the like by washing with water.

Moreover, as a method for the crosslinking treatment, physical crosslinking may be introduced between the molecular chains by performing a heat treatment. By performing the heat treatment, physical crosslinking occurs, and the mechanical strength of the resulting ion exchange membrane is increased. The method of heat treatment is not particularly limited, and a hot air dryer or the like is generally used. Although the temperature of heat processing is not specifically limited, In the case of polyvinyl alcohol, it is preferable that it is 50-250 degreeC. If the temperature of the heat treatment is less than 50 ° C., the mechanical strength of the obtained ion exchange membrane may be insufficient. The temperature is more preferably 80 ° C. or higher, and further preferably 100 ° C. or higher. When the temperature of the heat treatment exceeds 250 ° C., the crystalline polymer may be melted. The temperature is more preferably 230 ° C. or less, and further preferably 200 ° C. or less.

In the manufacturing method, both heat treatment and chemical crosslinking treatment may be performed, or only one of them may be performed. When both the heat treatment and the crosslinking treatment are performed, the crosslinking treatment may be performed after the heat treatment, the heat treatment may be performed after the crosslinking treatment, or both may be performed simultaneously.
After the heat treatment, a crosslinking treatment is performed. In particular, a film obtained by forming a film from a solution in which a vinyl alcohol copolymer solution is dissolved is heat-treated at a temperature of 100 ° C. or higher, and then water, alcohol, or a mixed solvent thereof. Among them, it is preferable from the viewpoint of mechanical strength of an ion exchange membrane obtained by performing a crosslinking treatment with a dialdehyde compound under acidic conditions.

(Ion exchange capacity)
In order to express sufficient ion exchange properties for use as a cation exchange membrane for electrodialysis, the ion exchange capacity of the resulting vinyl alcohol copolymer is preferably 0.30 meq / g or more, More preferably, it is 0.50 meq / g or more. The upper limit of the ion exchange capacity of the vinyl alcohol copolymer is preferably 3.0 meq / g or less because if the ion exchange capacity becomes too large, hydrophilicity increases and it becomes difficult to suppress the degree of swelling.

(Charge density)
Further, in order to develop sufficient electrical characteristics to be used as a cation exchange membrane for electrodialysis, the charge density of the obtained cation exchange membrane is preferably 0.6 mol / dm ³ or more. More preferably, it is 0.0 mol / dm ³ or more. As the charge density of the cation exchange membrane, a higher one is preferred, but in view of the membrane resistance, the one having a relatively low membrane resistance and expressing the charge density is preferred.

  The cation exchange membrane used in the present invention can be reinforced by being laminated with a support such as a nonwoven fabric, a woven fabric, or a porous material, if necessary.

(Anion exchange membrane used in electrodialysis treatment)
In the electrodialysis treatment of the present invention, the anion exchange membrane used together with the cation exchange membrane is not particularly limited, and is a membrane made of a polymer having a strongly basic group such as a quaternary ammonium group, a primary grade. A film made of a polymer having a weakly basic functional group such as an amino group, a secondary amino group, or a tertiary amino group can be appropriately selected and used.

(Organic wastewater)
Organic wastewater containing salts and organic matter treated by the method of the present invention includes organic wastewater such as chemical factory wastewater, food factory wastewater, wastewater treated with livestock waste, shellfish and other biological waste treatment wastewater, etc. These wastewaters often contain salts such as sodium chloride, potassium chloride, ammonium chloride, magnesium chloride, calcium chloride, and can be removed by the method of the present invention.

(SS removal process)
In the organic wastewater, suspended substances (SS) such as organic pollutants contained in the organic wastewater are first subjected to SS removal treatment such as biological treatment, coagulation sedimentation treatment, sand filtration treatment, and microfiltration membrane treatment. Removed. In order to reduce organic matter by removing suspended solids (SS) by SS removal treatment, electrodialysis treatment is performed, so that organic matter components leak into the electrodialysis treatment water due to the influence of SS and organic matter. Can be prevented.

  Specific examples of biological treatment include biological activated nitrification and denitrification in addition to the standard activated sludge method. By using these methods, organic substances are decomposed and nitrogen is removed. And can reduce suspended matter (SS) and BOD.

  The coagulation-precipitation process is a process that forms fine flocculent substances and colloidal substances in water with flocculants to form flocs (aggregates), and if necessary, further increases the flocs with a polymer flocculant and solid-liquid separation. Alternatively, it is a treatment method in which ionized heavy metals are chemically reacted with a flocculant such as a chelating agent to precipitate and remove. Suspended substances (SS), heavy metal ion components, and the like can be removed by the coagulation sedimentation treatment. COD can also be lowered.

  Sand filtration treatment is a filtration method that removes impurities by passing water to be treated through a sand filtration pond in which various layers of sand are laminated on a gravel-supported gravel layer. (SS), iron, manganese and the like can be removed.

  The microfiltration membrane treatment (aggregation MF membrane filtration treatment) is a treatment method using a microfiltration membrane, and preferably in combination with biological treatment, an inorganic flocculant is added to the treated water by biological treatment to cause aggregation. Goods should be filtered through a microfiltration membrane. When such a method is used, suspended substances (SS) can be removed from waste water.

(Electrodialysis)
In the method for treating organic wastewater according to the present invention, the electrodialysis tank has a cation exchange membrane and an anion exchange membrane arranged at least one of the cation membrane according to the present invention between the anode and the cathode. A known electrodialysis tank can be used without particular limitation as long as it has a basic structure. For example, an anion exchange membrane and a cation exchange membrane are alternately arranged, such as a filter press type or unit cell type having a basic structure in which a desalination chamber and a concentration chamber are formed by the ion exchange membrane and a chamber frame. Such an electrodialysis tank can be preferably used. The number of membranes used in the electrodialysis tank or the channel spacing (membrane spacing) between the desalting chamber and the concentrating chamber is appropriately selected depending on the type and amount of organic wastewater to be treated.

The organic waste water after the SS removal treatment is supplied to the electrodialysis apparatus, subjected to electrodialysis treatment, and separated into electrodialysis treatment water and electrodialysis concentrated water. The electrodialyzed water is desalted demineralized water, and the electrodialyzed concentrated water contains a high concentration of salt. The electrodialyzed water does not reduce the salt to a reusable water quality, but the salt concentration is sufficiently reduced compared to the raw water,
Even if released into rivers, the surrounding environment will not be affected by salt.
Electrodialyzed concentrated water contains a very high concentration of salt and has a small amount of water, so even if it is dried using an evaporator, the amount of energy used is small. It may be a salt, and the recovered crystal solidified salt may be disposed of.

  Hereinafter, examples will be given to describe the present invention in more detail, but the present invention is not limited to these examples. In the examples, “%” and “parts” are based on weight unless otherwise specified.

  The characteristics of the cation exchange membranes shown in Examples and Comparative Examples were measured by the following methods.

1) Membrane moisture content (H)
The dry weight of the ion exchange membrane was measured in advance, and then the wet weight was measured when it was immersed in deionized water and reached a swelling equilibrium. The membrane water content (H) was calculated by the following equation. _{H = <(W w -D w} ) / 1.0> / <(W w -D w) / 1.0+ (D w /1.3)>
Here, 1.0 and 1.3 indicate the specific gravity of water and polymer, respectively.
-H: membrane water content [-]
_Dw : dry weight of membrane [g]
W _w : wet weight of the film [g]

2) Measurement of cation exchange capacity A cation exchange membrane is immersed in a 1 mol / L aqueous HCl solution for 10 hours or more. Thereafter, the hydrogen ion type was replaced with the sodium ion type with 1 mol / L NaNO ₃ aqueous solution, and the liberated hydrogen ions were quantified by acid-base titration (Amol).

Next, the same cation exchange membrane is immersed in a 1 mol / L NaCl aqueous solution for 4 hours or more, washed thoroughly with ion exchange water, dried in a hot air drier at 105 ° C. for 8 hours, and the weight when dried W (G) was measured.
The ion exchange capacity was calculated by the following formula.
・ Ion exchange capacity = A × 1000 / W [mmol / g-dry membrane]

3) Measurement of the salt in the polyvinyl alcohol copolymer The amount of the salt in the polyvinyl alcohol copolymer was determined by Soxhlet extraction of the film before crosslinking of the polyvinyl alcohol copolymer with a methanol solution for 48 hours. The product was dried and then measured by ion chromatography ICS-5000 (manufactured by DIONEX).

4) Measurement of membrane resistance The membrane resistance was measured by sandwiching a cation exchange membrane in a two-chamber cell having a platinum black electrode plate as shown in Fig. 2, and filling a 0.5 mol / L-NaCl solution on both sides of the membrane. The resistance between the electrodes at 25 ° C. was measured by (frequency 10 cycles / second), and was determined by the difference between the resistance between the electrodes and the resistance between the electrodes when no cation exchange membrane was installed. The membrane used for the above measurement was previously equilibrated in a 0.5 mol / L-NaCl solution.

5) Measurement of domain size A cation exchange membrane immersed in distilled water was cut into a 1 cm square to prepare a measurement sample. This measurement sample was stained with lead acetate (II) and then observed using a TEM (transmission electron microscope) to obtain an image of a particle group in the measurement sample. The obtained image was subjected to image processing using image processing software “WINROOF” manufactured by Mitani Corporation, and the maximum particle size of each particle was determined. The maximum particle size was determined for about 400 particles, and the particle size at which the cumulative frequency of the maximum particle size was 50% was defined as the domain size of the anionic group polymer segment of the cation exchange membrane.

<Preparation of PVA-1 (Synthesis of polyvinyl alcohol copolymer having a mercapto group at the molecular terminal)>
Polyvinyl alcohol (PVA-1) having a mercapto group at the molecular end shown in Table 1 was synthesized by the method described in JP-A-59-187003. Table 1 shows the polymerization degree and saponification degree of PVA-1.

<NaSS-1 (anionic monomer)>
The polystyrene sulfonate sodium monomer (NaSS: manufactured by Tosoh Corporation) shown in Table 2 was used as it was. The salt content was measured by ion chromatography ICS-5000 (manufactured by DIONEX). The impurities in the monomer other than the total salt amount shown in Table 2 were moisture.

<Preparation of NaSS-2>
1000 g of sodium polystyrene sulfonate monomer (NaSS: manufactured by Tosoh Corp.), 950 g of pure water, 40 g of sodium hydroxide, 1 g of sodium nitrate were dissolved at 60 ° C. for 1 hour, cooled to 20 ° C. and recrystallized. Thereafter, the polystyrenesulfonic acid monomer crystals were separated by centrifugal filtration, and the crystals were dried to obtain NaSS-2 (purified polystyrenesulfonic acid monomer) shown in Table 2. The salt content was measured by ion chromatography ICS-5000 (manufactured by DIONEX).

<Synthesis of P-1 (anionic block copolymer)>
In a 1 L four-necked separable flask equipped with a reflux condenser and a stirring blade, 660 g of water, 80 g of PVA-1 shown in Table 1 as a vinyl alcohol polymer having a mercapto group at the end, and 46. 6 g was charged and heated to 95 ° C. with stirring to dissolve the vinyl alcohol polymer and NaSS-1. The system was purged with nitrogen for 30 minutes while bubbling nitrogen into the aqueous solution. After nitrogen substitution, the solution was cooled to 90 ° C., and 13 ml of a 5.4% solution of 2,2′-azobis [2-methyl-N (2-hydroxyethyl) propionamide] was sequentially added to the above aqueous solution over 1.5 hours. After the addition and the block copolymerization was started and proceeded, the system temperature was maintained at 90 ° C. for 1 hour to further proceed the polymerization, followed by cooling to a solid content concentration of 15% PVA- (b) -p -A sodium styrenesulfonate aqueous solution was obtained. A part of the obtained aqueous solution was dried, dissolved in heavy water, and subjected to ¹ H-NMR measurement at 400 MHz. As a result, the amount of modification of the sodium parastyrenesulfonate unit was 10 mol%. Table 3 shows the properties of the obtained anionic block copolymer.

<Synthesis of P-2>
The type and amount of the anionic group-containing monomer were changed to those shown in Table 3. Except for this, a PVA- (b) -p-sodium styrenesulfonate aqueous solution having a solid concentration of 15% was obtained in the same manner as P-1. Table 3 shows the properties of the obtained anionic block copolymer.

<Synthesis of P-3>
In a 1 L four-necked separable flask equipped with a reflux condenser and a stirring blade, 616 g of water, 80 g of PVA-1 shown in Table 1 as a vinyl alcohol polymer having a mercapto group at the end, and 46. NaSS-1 were obtained. 6 g was charged and heated to 95 ° C. with stirring to dissolve the vinyl alcohol polymer and NaSS-1, and then cooled to room temperature. 1/2 N sulfuric acid was added to the aqueous solution to adjust the pH to 3.0. The system was heated to 90 ° C., and the system was purged with nitrogen for 30 minutes while bubbling nitrogen into the aqueous solution. After nitrogen substitution, 63 mL of a 2.5% aqueous solution of potassium persulfate was sequentially added to the aqueous solution over 1.5 hours to start and proceed with block copolymerization, and then the system temperature was increased to 90 ° C. for 1 hour. The polymerization was further continued to proceed, followed by cooling to obtain a PVA- (b) -p-sodium styrenesulfonate block copolymer aqueous solution having a solid concentration of 15%. A part of the obtained aqueous solution was dried, dissolved in heavy water, and subjected to ¹ H-NMR measurement at 400 MHz. As a result, the amount of modification of the sodium p-styrenesulfonate unit was 10 mol%. Table 3 shows the properties of the obtained anionic block copolymer.

<Synthesis of P-4 to 5>
The type and amount of the anionic group-containing monomer were changed to those shown in Table 3. Except for this, a PVA- (b) -p-sodium styrenesulfonate aqueous solution having a solid concentration of 15% was obtained in the same manner as P-3. Table 3 shows the properties of the obtained anionic block copolymer.

<Synthesis of P-6 (anionic random copolymer)>
A 6 L separable flask equipped with a stirrer, temperature sensor, dropping funnel and reflux condenser was charged with 2450 g of vinyl acetate, 762 g of methanol, and 27 g of sodium 2-acrylamido-2-methylpropanesulfonate (AMPS) under stirring. After the system was purged with nitrogen, the internal temperature was raised to 60 ° C. To this system, 20 g of methanol containing 0.8 g of 2,2′-azobisisobutyronitrile (AIBN) was added to initiate the polymerization reaction. While adding 568 g of methanol solution containing 25% by mass of sodium 2-acrylamido-2-methylpropanesulfonate (AMPS) to the system from the start of polymerization, the polymerization reaction was stopped for 4 hours, and then the polymerization reaction was stopped. The solid content concentration in the system when the polymerization reaction was stopped, that is, the solid content with respect to the entire polymerization reaction slurry was 30% by mass. Subsequently, methanol vapor was introduced into the system to drive out unreacted vinyl acetate monomer, thereby obtaining a methanol solution containing 30% by mass of a vinyl ester copolymer.

  In a methanol solution containing 30% by mass of this vinyl ester copolymer, the molar ratio of sodium hydroxide to vinyl acetate units in the copolymer is 0.02, and the solid content concentration of the vinyl ester copolymer is 30% by mass. Then, a methanol solution containing 10% by mass of methanol and sodium hydroxide was added in this order with stirring, and the saponification reaction was started at 40 ° C.

Immediately after the saponification reaction has occurred, a gelled product is formed and taken out from the reaction system and pulverized. Then, when 1 hour has passed since the gelated product was formed, methyl acetate was added to the pulverized product. By carrying out neutralization, an aqueous solution of a random copolymer of polyvinyl alcohol-poly (sodium 2-acrylamido-2-methylpropanesulfonate) in a swollen state was obtained. To this swollen anionic polymer, 6 times the amount of methanol (6 times the bath ratio) of methanol was added and washed under reflux for 1 hour, and the polymer was collected by filtration. The polymer was dried at 65 ° C. for 16 hours. When the obtained polymer was dissolved in heavy water and subjected to ¹ H-NMR measurement at 400 MHz, the content of the anionic monomer in the anionic polymer, that is, the monomer in the polymer The ratio of the number of sodium 2-acrylamido-2-methylpropanesulfonate monomer units to the total number of units was 5 mol%. Table 4 shows the properties of the obtained anionic random copolymer.

<Production of CEM-1>
The resin of P-3 was diluted to a concentration of 10 wt%, and the resin from which salts were removed by reprecipitation with 1 volume of methanol of the resin solution was taken out. At this time, the salt content (C) was 4.5 wt%. Next, a necessary amount of distilled water was added to prepare an aqueous solution having a concentration of 15 wt%. This aqueous solution was poured into a cast board made of acrylic having a length of 270 mm and a width of 210 mm to remove excess liquid and bubbles, and then dried on a hot plate at 50 ° C. for 24 hours to prepare a film.

  The film thus obtained was heat treated at 160 ° C. for 30 minutes to cause physical crosslinking. Subsequently, the film was immersed in an aqueous electrolyte solution of 2 mol / L sodium sulfate for 24 hours. Concentrated sulfuric acid was added to the aqueous solution so that the pH was 1, and then the film was immersed in a 1.0% by volume glutaraldehyde aqueous solution and stirred with a stirrer at 25 ° C. for 24 hours to carry out a crosslinking treatment. Here, as the glutaraldehyde aqueous solution, a product obtained by diluting “glutaraldehyde” (25% by volume) manufactured by Ishizu Pharmaceutical Co., Ltd. with water was used. After the crosslinking treatment, the film was immersed in deionized water, and the film was immersed until the film reached a swelling equilibrium while exchanging the deionized water several times in the middle to obtain a cation exchange membrane.

(Evaluation of ion exchange membrane)
The cation exchange membrane thus prepared was cut into a desired size to prepare a measurement sample. Using the obtained measurement sample, the membrane water content, the cation exchange capacity, the membrane resistance, and the phase separation domain size were measured according to the above methods. The results obtained are shown in Table 5.

<Production of CEM-2>
The resin of P-3 was diluted to a concentration of 10 wt%, and the resin from which salts were removed by reprecipitation with twice the volume of methanol as the resin solution was taken out. Next, a necessary amount of distilled water was added to prepare an aqueous solution having a concentration of 15 wt%. This aqueous solution was poured onto an acrylic cast plate having a length of 270 mm and a width of 210 mm to remove excess liquid and bubbles, and then dried on a hot plate at 50 ° C. for 24 hours to prepare a film. At this time, the salt content (C) was 4.0 wt%. Except for this, the membrane characteristics of the cation exchange membrane were measured in the same manner as CEM-1. The obtained measurement results are shown in Table 5.

<Preparation of CEM-3>
An aqueous solution of P-2 was poured onto an acrylic cast plate having a length of 270 mm and a width of 210 mm to remove excess liquid and bubbles, and then dried on a hot plate at 50 ° C. for 24 hours to prepare a film. At this time, the salt content (C) was 2.8 wt%. Except for this, the membrane characteristics of the cation exchange membrane were measured in the same manner as CEM-1. The obtained measurement results are shown in Table 5.

<CEM-4 production>
In CEM-3, the membrane characteristics of the cation exchange membrane were measured in the same manner as in CEM-3 except that the heat treatment temperature was changed as shown in Table 5. The obtained measurement results are shown in Table 5.

<CEM-5 production>
The resin of P-3 was diluted to a concentration of 10 wt%, and the resin from which salts were removed by reprecipitation with 5 times the volume of methanol of the resin solution was taken out. Next, a necessary amount of distilled water was added to prepare an aqueous solution having a concentration of 15 wt%. This aqueous solution was poured onto an acrylic cast plate having a length of 270 mm and a width of 210 mm to remove excess liquid and bubbles, and then dried on a hot plate at 50 ° C. for 24 hours to prepare a film. At this time, the salt content (C) was 2.0 wt%. Except for this, the membrane characteristics of the cation exchange membrane were measured in the same manner as CEM-1. The obtained measurement results are shown in Table 5.

<CEM-6 production>
The P-3 resin was diluted to a concentration of 10 wt%, and the resin from which salts were removed by reprecipitation with 10 times the volume of methanol of the resin solution was taken out. Next, a necessary amount of distilled water was added to prepare an aqueous solution having a concentration of 15 wt%. This aqueous solution was poured into a cast board made of acrylic having a length of 270 mm and a width of 210 mm to remove excess liquid and bubbles, and then dried on a hot plate at 50 ° C. for 24 hours to prepare a film. At this time, the salt content (C) was 1.5 wt%. Except for this, the membrane characteristics of the cation exchange membrane were measured in the same manner as CEM-1. The obtained measurement results are shown in Table 5.

<Production of CEM-7 to 11>
The membrane characteristics of the cation exchange membrane were measured in the same manner as CEM-1 except that the cation exchange resin was changed to the contents shown in Table 5. The obtained measurement results are shown in Table 5.

  1 (a), 1 (b), 1 (c), 1 (d) and 1 (e) are TEM photographs of cation exchange membranes using block copolymers having different salt contents. (See Table 5 for salt content). From the TEM photographs of FIGS. 1 (a) to 1 (e), the phase separation structure varies depending on the salt content, and the domain size decreases with decreasing salt-containing weight (C) / block copolymer weight (P). I understand that In particular, in FIG. 1 (b) [CEM-7] in which the weight (C) of the contained salt is the smallest at a modification amount of 10 mol%, the compatibility of the film is improved and the domain size is very small, 4 nm. . On the other hand, in FIG. 1 (C) [CEM-8] having the largest salt content (C), phase separation was severe and voids were generated.

From the results shown in Table 5, the film using the block copolymer (P) having a salt-containing weight (C) of 4.0% or less is a film having a domain size of 150 nm or less and a low film resistance. It turns out that it is excellent as an ion exchange membrane (CEM-1-7). Furthermore, it can be seen that a film having a salt content weight (C) of 3.5% or less has a domain size of 130 nm or less and a low film resistance (CEM-2 to 7). On the other hand, a cation exchange membrane using a block copolymer having a salt content of more than 4.0% has a domain size larger than 150 nm, a high membrane resistance, and exhibits characteristics as a cation exchange membrane. None (CEM-8-10). In particular, when the salt content (C) is large, the phase separation of the polymer segment of the membrane is severe, and voids are generated in the entire ion exchange membrane, and satisfactory characteristics as an ion exchange membrane are not expressed (CEM-8). . In CEM-9, purified NaSS-2 is used, but since KPS is used as the polymerization initiator, the salt content in the obtained cation exchange resin is high.
On the other hand, a membrane (CEM-11) using a random copolymer P-6 that was not confirmed to be completely compatible with microphase separation was a block copolymer P- with a small phase separation domain size. Film resistance is higher than 5 (CEM-5) (Table 5). From this, it can be seen that a block copolymer having a phase separation domain and having a phase separation domain size (X) exceeding 0, that is, X> 0 is important for the expression of membrane performance.

<Example 1>
This was performed using the apparatus shown in FIG. The apparatus is composed of a biological treatment tank 1, an electrodialysis apparatus 3, and a cartridge filter-2 disposed between the biological treatment tank 1 and the electrodialysis apparatus 3, and has a BOD concentration of 300 mg / L. The supernatant treatment liquid after the biological treatment in the biological treatment tank 1 was supplied to the electrodialysis apparatus 3 after the SS removal treatment with the cartridge filter 2 having a pore diameter of 10 μm. The electrodialysis apparatus 3 is a small electrodialysis apparatus CH-0 type (manufactured by AGC Engineering Co., Ltd.) using CEM-1 as a cation exchange membrane and Selemion AMV (manufactured by AGC Engineering Co., Ltd.) as an anion exchange membrane. The stack was assembled by alternately arranging the cathode and anode electrodes, and the organic wastewater was subjected to a desalting test. At this time, the SS removal treated water contained BOD concentration: 20 mg / L, TDS (evaporation residue component concentration): 3000 ppm. This filtered water was supplied to the desalting chamber of the electrodialyzer 3 and electrodialyzed at 25 ° C. with a current density of 1 to ^{2 A} / dm ^{2 in} one pass for 7 hours. Table 6 shows the results of measuring the desalting rate after 7 hours and the degree of organic contamination (the rate of increase in voltage after 7 hours of operation from the voltage at the start).

<Examples 2 to 7>
A desalting test of organic wastewater was performed in the same manner as in Example 1 except that the cation exchange membrane used was changed to the contents shown in Table 6. The results obtained are shown in Table 6.

<Comparative Examples 1-4>
An organic matter desalting test was conducted in the same manner as in Example 1 except that the cation exchange membrane used was changed to the contents shown in Table 6. The results obtained are shown in Table 6.

<Comparative Example 5>
The measurement was performed under the same conditions as in Example 1 using a commercial product CMV (manufactured by AGC Engineering Co., Ltd.) as the cation exchange membrane. The results are shown in Table 6.

<Comparative Example 6>
The measurement was performed using the apparatus shown in FIG. The apparatus is composed of a biological treatment tank 1, an RO membrane apparatus 6, and a cartridge filter-2 disposed between the biological treatment tank 1 and the RO membrane apparatus 6, and has a BOD concentration of 300 mg / L. The supernatant processing solution after the biological treatment was performed in the biological treatment tank 1 was supplied to the RO membrane device 6 after the SS removal treatment with the cartridge filter 2 having a pore diameter of 10 μm. Organic wastewater using RO membrane separator 6 (low pressure aromatic polyamide RO membrane “ES-10” manufactured by Nitto Denko) under conditions of pressure: 0.75 MPa, water flow rate: 80 L / h, recovery rate: 75% A desalting test was conducted. At this time, the SS removal treated water contained BOD concentration: 20 mg / L and TDS: 3000 ppm. At this time, the water flow rate decreased to 40 L / h in 3 hours after the start of the treatment, and the degree of organic contamination was intense.

  As is clear from the results in Table 6, in Examples 1 to 7, the desalination rate is superior to Comparative Examples 1 to 4, and the voltage increase rate is low compared to Comparative Example 5, Excellent organic contamination.

  As described above, cation exchange having a microphase separation structure composed of a vinyl alcohol copolymer having an anionic polymer segment and a vinyl alcohol polymer segment and having a domain size in a range of 0 nm <X ≦ 150 nm. The membrane is effective in separating organic wastewater into electrodialyzed concentrated water and electrodialyzed water, and has excellent resistance to organic contamination, enabling stable long-term electrodialysis. Since it can be performed, it has industrial applicability.

  Although the preferred embodiments of the present invention have been described above by way of example, those skilled in the art can make various modifications, additions and substitutions without departing from the scope and spirit of the present invention disclosed in the claims. It will be understandable.

A ion exchange membrane B platinum electrode C NaCl aqueous solution D water bath E LCR meter

Claims (6)

The organic wastewater containing salts and organic substances is subjected to SS removal treatment, and then the organic wastewater after the SS removal treatment is subjected to electrodialysis treatment to be separated into electrodialysis concentrated water and electrodialysis treatment water. In the method of treating organic wastewater,
As a cation exchange membrane in the electrodialysis treatment,
A microphase-separated structure comprising an anionic polymer segment having an anionic group and a vinyl alcohol copolymer having a vinyl alcohol polymer segment and having a domain size (X) in the range of 0 nm <X ≦ 150 nm. A method for treating organic wastewater, comprising using a cation exchange membrane.   The vinyl alcohol polymer segment is a segment formed from a vinyl alcohol polymer not containing an anionic group, and electrodialysis treatment is performed using a cation exchange membrane containing a vinyl alcohol copolymer having the segment. The method for treating organic wastewater according to claim 1, wherein the treatment is performed.   The method for treating organic wastewater according to claim 1 or 2, wherein a crosslinked structure is introduced into the vinyl alcohol copolymer.   The said vinyl alcohol-type copolymer is an anionic block copolymer which has an anionic polymer block which has a vinyl alcohol polymer block and an anionic group, The any one of Claims 1-3 characterized by the above-mentioned. A method for treating organic wastewater as described in 1.   The said vinyl alcohol-type copolymer is an anionic graft copolymer which has a vinyl alcohol polymer block and an anionic polymer block which has an anionic group, The any one of Claims 1-3 characterized by the above-mentioned. A method for treating organic wastewater as described in 1. The SS removal treatment comprises one or more treatments selected from the group consisting of biological treatment, coagulation sedimentation treatment, sand filtration treatment, and microfiltration membrane treatment for organic wastewater, or a combination of two or more. The processing method of the organic wastewater of any one of -5.

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