Classifications

• • C—CHEMISTRY; METALLURGY
  • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
  • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
  • C02F1/00—Treatment of water, waste water, or sewage
  • C02F1/44—Treatment of water, waste water, or sewage by dialysis, osmosis or reverse osmosis
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D65/00—Accessories or auxiliary operations, in general, for separation processes or apparatus using semi-permeable membranes
  • B01D65/02—Membrane cleaning or sterilisation ; Membrane regeneration
  • B01D65/06—Membrane cleaning or sterilisation ; Membrane regeneration with special washing compositions
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D65/00—Accessories or auxiliary operations, in general, for separation processes or apparatus using semi-permeable membranes
  • B01D65/08—Prevention of membrane fouling or of concentration polarisation
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D65/00—Accessories or auxiliary operations, in general, for separation processes or apparatus using semi-permeable membranes
  • B01D65/10—Testing of membranes or membrane apparatus; Detecting or repairing leaks
  • B01D65/106—Repairing membrane apparatus or modules
  • B01D65/108—Repairing membranes
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D67/00—Processes specially adapted for manufacturing semi-permeable membranes for separation processes or apparatus
  • B01D67/0002—Organic membrane manufacture
  • B01D67/0006—Organic membrane manufacture by chemical reactions
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D67/00—Processes specially adapted for manufacturing semi-permeable membranes for separation processes or apparatus
  • B01D67/0081—After-treatment of organic or inorganic membranes
  • B01D67/0093—Chemical modification
  • B01D67/00933—Chemical modification by addition of a layer chemically bonded to the membrane
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D69/00—Semi-permeable membranes for separation processes or apparatus characterised by their form, structure or properties; Manufacturing processes specially adapted therefor
  • B01D69/02—Semi-permeable membranes for separation processes or apparatus characterised by their form, structure or properties; Manufacturing processes specially adapted therefor characterised by their properties
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D69/00—Semi-permeable membranes for separation processes or apparatus characterised by their form, structure or properties; Manufacturing processes specially adapted therefor
  • B01D69/12—Composite membranes; Ultra-thin membranes
  • B01D69/1214—Chemically bonded layers, e.g. cross-linking
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D69/00—Semi-permeable membranes for separation processes or apparatus characterised by their form, structure or properties; Manufacturing processes specially adapted therefor
  • B01D69/12—Composite membranes; Ultra-thin membranes
  • B01D69/125—In situ manufacturing by polymerisation, polycondensation, cross-linking or chemical reaction
  • B01D69/1251—In situ manufacturing by polymerisation, polycondensation, cross-linking or chemical reaction by interfacial polymerisation
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D71/00—Semi-permeable membranes for separation processes or apparatus characterised by the material; Manufacturing processes specially adapted therefor
  • B01D71/06—Organic material
  • B01D71/56—Polyamides, e.g. polyester-amides
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D2321/00—Details relating to membrane cleaning, regeneration, sterilization or to the prevention of fouling
  • B01D2321/16—Use of chemical agents
  • B01D2321/162—Use of acids
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D2321/00—Details relating to membrane cleaning, regeneration, sterilization or to the prevention of fouling
  • B01D2321/16—Use of chemical agents
  • B01D2321/164—Use of bases
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D2321/00—Details relating to membrane cleaning, regeneration, sterilization or to the prevention of fouling
  • B01D2321/16—Use of chemical agents
  • B01D2321/168—Use of other chemical agents
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D2325/00—Details relating to properties of membranes
  • B01D2325/20—Specific permeability or cut-off range
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D61/00—Processes of separation using semi-permeable membranes, e.g. dialysis, osmosis or ultrafiltration; Apparatus, accessories or auxiliary operations specially adapted therefor
  • B01D61/02—Reverse osmosis; Hyperfiltration ; Nanofiltration
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D61/00—Processes of separation using semi-permeable membranes, e.g. dialysis, osmosis or ultrafiltration; Apparatus, accessories or auxiliary operations specially adapted therefor
  • B01D61/14—Ultrafiltration; Microfiltration

Definitions

• the present invention relates to a method for treating a semipermeable membrane useful for selective separation of a liquid mixture, and more specifically, to a method for treating a semipermeable membrane having a separation functional layer containing polyamide.
• Semipermeable membranes used to separate liquid mixtures include microfiltration membranes, ultrafiltration membranes, nanofiltration membranes, and reverse osmosis membranes. These membranes are used, for example, to produce drinking water from water containing salt or harmful substances, to produce ultrapure water for industrial use, to treat wastewater, or to recover valuable materials.
• a typical composite semipermeable membrane has a microporous support membrane and a separation functional layer that is made of a crosslinked aromatic polyamide obtained by a polycondensation reaction between a polyfunctional amine and a polyfunctional acid halide and covers the microporous support membrane, and has high permeability and selective separation properties.
• the permeability of the semipermeable membrane decreases due to organic fouling, inorganic fouling (scaling), and biofouling caused by organic substances, inorganic substances, and microorganisms present in the liquid mixture during use.
• the membrane is washed with chemicals containing acids and alkalis.
• oxidizing agents such as chlorine are sometimes supplied to clean pipes, etc., and these oxidizing agents may also be mixed into the liquid supplied to the semipermeable membrane, causing contact between the semipermeable membrane and the oxidizing agent. Therefore, even if the substances that cause fouling are removed by washing with acids or alkalis and the permeability is restored, the removal performance of the semipermeable membrane may decrease as a result of contact between the semipermeable membrane and chemicals such as oxidizing agents.
• Patent Document 1 cites that the degradation of polyamide membranes by oxidizing agents is caused by the cleavage of C-N bonds (amide bonds), which causes the sieve structure to collapse. Patent Document 1 also discloses a method for improving the rejection of such a deteriorated membrane, in which an amino compound is bound to a carboxyl group generated at the cleavage site of the amide bond.
• the rejection improvement method described in Patent Document 1 includes a step of passing a first organic compound having a molecular weight of less than 200, a second organic compound having a molecular weight of 200 or more and less than 500, and a third organic compound having a molecular weight of 500 or more through a polyamide membrane.
• Examples of the first and second organic compounds include aromatic amino compounds such as aniline and diaminobenzene, and aliphatic amino compounds such as methylamine and 1,9-diaminononane.
• Examples of the third organic compounds include those having a carboxyl group, an amino group, a hydroxyl group, or a cyclic structure, such as tannic acid and peptides.
• the first and second organic compounds which have low molecular weights, are highly soluble in water and react with the carboxyl groups of the membrane to bind to the reverse osmosis membrane and form an insoluble salt, which plugs holes caused by deterioration of the membrane, while the third organic compound plugs areas of major deterioration in the membrane, and both increase the rejection rate of the membrane.
• the objective of the present invention is to provide a treatment method that can improve the removal performance of a semipermeable membrane whose removal performance does not reach a desired level or whose removal performance has deteriorated.
• the semipermeable membrane treatment method, the semipermeable membrane element manufacturing method and treatment device, and the fluid treatment method and fluid treatment device using the semipermeable membrane element of the present invention have any one of the following configurations.
• a method for treating a semipermeable membrane having a separating functional layer containing a polyamide comprising the steps of: (a) attaching a polyfunctional amine to the polyamide; (b) bonding at least one of a polyfunctional carboxylic acid and a polyfunctional acid halide to the polyamide; The processing method according to claim 1, [2] The method according to the above [1], wherein the step (b) is carried out after the step (a).
• step (a) comprises covalently bonding the polyfunctional amine to the polyamide with a condensing agent.
• step (b) includes covalently bonding the polyfunctional carboxylic acid to the polyamide with a condensing agent.
• step (a) and the step (b) are alternately repeated two or more times.
• step (a) and the step (b) are carried out on a semipermeable membrane that has been contacted with at least one agent selected from the group consisting of an acid having a pH of 4 or less, an alkali having a pH of 10 or more, and an oxidizing agent.
• a method for treating a semipermeable membrane having a separating functional layer containing a polyamide comprising the steps of: (A) contacting the separation functional layer with an aqueous solution containing a polyfunctional amine and a condensing agent; (B) contacting the separation functional layer with at least one of an aqueous solution containing a polyfunctional carboxylic acid and an organic solvent solution containing a polyfunctional acid halide;
• the processing method according to claim 1 [11] The method according to the above [10], wherein the step (B) is carried out after the step (A).
• a fluid treatment device that treats a fluid using a semipermeable membrane element obtained by the method for producing a semipermeable membrane element according to the above [13].
• the present invention makes it possible to improve the removal performance of a semipermeable membrane whose removal performance does not reach the desired level or whose removal performance has deteriorated.
• This treatment method can improve the performance of semipermeable membranes that do not meet the desired performance or that have lost the desired performance due to contact with a chemical solution.
• the polyamide contained in the separation functional layer of the semipermeable membrane according to this embodiment can be hydrolyzed by contact with an oxidizing agent mixed in the raw water supplied to the semipermeable membrane.
• the hydrolyzed portion becomes a coarse pore, allowing the substance to be removed to pass through.
• carboxyl groups are exposed by the hydrolysis of the polyamide.
• a polyfunctional amine and at least one of a polyfunctional carboxylic acid and a polyfunctional acid halide are bonded to a polyamide, thereby reducing the size of the coarse pores and improving the performance of the semipermeable membrane. More specifically, an amide bond can be formed between a polyfunctional amine and a terminal carboxy group in the polyamide separation functional layer, and an amide bond can be formed between a polyfunctional carboxylic acid and a polyfunctional acid halide and a terminal amino group in the polyamide separation functional layer. Furthermore, by repeating the step of bonding at least one of the polyfunctional amine, the polyfunctional carboxylic acid, and the polyfunctional acid halide, the coarse pores can be further reduced in size.
• polyfunctional amine binding step (a) Examples of polyfunctional amines include polyfunctional aromatic amines and polyfunctional aliphatic amines.
• a polyfunctional aromatic amine is an aromatic amine that has at least two amino groups, either primary or secondary, in one molecule, and at least one of the amino groups is a primary amino group.
• polyfunctional aromatic amines include compounds in which two amino groups are bonded to an aromatic ring at the ortho, meta, or para positions, such as o-phenylenediamine, m-phenylenediamine, p-phenylenediamine, o-xylylenediamine, m-xylylenediamine, p-xylylenediamine, o-diaminopyridine, m-diaminopyridine, and p-diaminopyridine, 1,3,5-triaminobenzene, 1,2,4-triaminobenzene, 3,5-diaminobenzoic acid, 3-aminobenzylamine, and 4-aminobenzylamine.
• m-phenylenediamine, p-phenylenediamine, or 1,3,5-triaminobenzene is preferably used from the viewpoint of obtaining a semipermeable membrane with excellent selective separation properties, permeability, and heat resistance.
• a polyfunctional aliphatic amine is an aliphatic amine that has two or more amino groups in one molecule.
• Examples of polyfunctional aliphatic amines include piperazine and its derivatives, and ethylenediamine.
• R 1 and R 2 are each —H or —(CH 2 ) n —CH 3 , where n is an integer from 0 to 3.
• piperazine and its derivatives examples include piperazine, 2,5-dimethylpiperazine, 2-methylpiperazine, 2,6-dimethylpiperazine, 2,3,5-trimethylpiperazine, 2,5-diethylpiperazine, 2,3,5-triethylpiperazine, 2-n-propylpiperazine, and 2,5-di-n-butylpiperazine.
• piperazine or dimethylpiperazine is preferably used.
• At least one type of polyfunctional amine may be used, and two or more types of compounds may be selected from polyfunctional aromatic amines and polyfunctional aliphatic amines.
• step (a) may include covalently bonding the polyfunctional amine to the polyamide with a condensing agent.
• this step can be carried out as step (A) of contacting the separation functional layer with an aqueous solution containing the polyfunctional amine and the condensing agent.
• the contact with the separation functional layer is carried out by contacting the aqueous solution with the surface of the separation functional layer.
• the concentration of the polyfunctional amine in the polyfunctional amine aqueous solution is preferably 0.005% by mass or more and 0.5% by mass or less, and more preferably 0.01% by mass or more and 0.3% by mass or less.
• the concentration of the condensing agent in the polyfunctional amine aqueous solution is preferably 0.001% by mass or more and 1.0% by mass or less, and more preferably 0.005% by mass or more and 0.3% by mass or less.
• concentration of the condensing agent is 0.001% by mass or more, it is possible to sufficiently generate bonds between the terminal carboxyl groups present in the polyamide separation functional layer and the polyfunctional amine.
• the temperature be 10°C or higher and 50°C or lower, and more preferably 20°C or higher and 45°C or lower.
• the pH of the polyfunctional amine aqueous solution may be 10 or more and 13 or less.
• a polyfunctional acid halide is an acid halide that has two or more halogenated carbonyl groups in one molecule.
• Polyfunctional acid halides can form amide bonds by reacting with terminal amino groups.
• polyfunctional acid halides examples include halides of oxalic acid, malonic acid, maleic acid, fumaric acid, glutaric acid, 1,3,5-cyclohexanetricarboxylic acid, 1,3-cyclohexanedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, trimesic acid, 1,2,4-benzenetricarboxylic acid, 1,3-benzenedicarboxylic acid, and 1,4-benzenedicarboxylic acid.
• acid chlorides are preferred.
• the polyfunctional acid halide is preferably a polyfunctional aromatic acid halide.
• a polyfunctional aromatic acid halide refers to an aromatic acid halide having at least two, preferably two to four, carbonyl chloride groups in one molecule (i.e., a polyfunctional aromatic acid chloride).
• a trifunctional acid halide may be trimesic acid chloride
• a bifunctional acid chloride may be biphenyldicarboxylic acid dichloride, azobenzenedicarboxylic acid dichloride, terephthalic acid chloride, isophthalic acid chloride, naphthalenedicarboxylic acid chloride, and the like.
• These polyfunctional aromatic acid halides may be used alone or in combination of two or more compounds.
• step (b) the polyfunctional carboxylic acid is used as an aqueous solution, and the polyfunctional acid halide is used as an organic solvent solution.
• this step can be carried out as step (B) in which the separation functional layer is contacted with at least one of an aqueous solution containing a polyfunctional carboxylic acid and an organic solvent solution containing a polyfunctional acid halide.
• Contact with the separation functional layer is carried out by contacting the surface of the separation functional layer with an aqueous solution or an organic solvent solution, similar to step (A).
• the contact time of the polyfunctional carboxylic acid aqueous solution or the organic solvent solution containing a polyfunctional acid halide (hereinafter also referred to as a polyfunctional acid halide solution) with the film surface is preferably from 1 minute to 6 hours per treatment, and more preferably from 10 minutes to 3 hours.
• the concentration of the polyfunctional carboxylic acid in the polyfunctional carboxylic acid aqueous solution is preferably 0.005% by mass or more and 0.5% by mass or less, and more preferably 0.01% by mass or more and 0.3% by mass or less.
• Step (b) may include covalently bonding the polyfunctional carboxylic acid to the polyamide using a condensing agent.
• concentration of the condensing agent in the aqueous polyfunctional carboxylic acid solution is preferably 0.001% by mass or more and 1.0% by mass or less, and more preferably 0.005% by mass or more and 0.3% by mass or less.
• concentration of the condensing agent is 0.001% by mass or more, it is possible to sufficiently bond the terminal amino groups present in the polyamide separation functional layer with the polyfunctional carboxylic acid.
• the temperature of the aqueous polyfunctional carboxylic acid solution is preferably 10°C or higher and 50°C or lower, and more preferably 20°C or higher and 45°C or lower, in order to promote bonding between the amino group and the polyfunctional carboxylic acid and to suppress the effect of heat on the semipermeable membrane.
• the pH of the polyfunctional carboxylic acid aqueous solution may be 10 or more and 13 or less.
• the organic solvent for dissolving the polyfunctional acid halide is immiscible with water, has a solubility parameter (SP value) of 15.2 (MPa) 1/2 or more, and an octanol/water partition coefficient (logP) of 3.2 or more.
• SP value solubility parameter
• logP octanol/water partition coefficient
• organic solvents that satisfy the above conditions include octane, nonane, decane, undecane, dodecane, isododecane, tridecane, tetradecane, heptadecane, hexadecane, isodecane, cyclooctane, isooctane, ethylcyclohexane, 1-octene, 1-decene, and the like, either alone or in mixtures thereof.
• the concentration of the polyfunctional acid halide in the organic solvent solution containing the polyfunctional acid halide is preferably 0.005% by mass or more and 0.5% by mass or less, and more preferably 0.01% by mass or more and 0.3% by mass or less.
• the temperature of the organic solvent solution containing the polyfunctional acid halide is high, the bonding between the amino group and the polyfunctional acid halide is easily promoted, but if the temperature is too high, the semipermeable membrane is affected by the heat, so it is preferable that the temperature be 10°C or higher and 50°C or lower, and more preferably 20°C or higher and 45°C or lower.
• step (b) it is preferable to carry out step (b) after step (a). Since carboxy groups are exposed in the coarse pores due to hydrolysis of the polyamide, by carrying out step (b) after step (a), it is possible to efficiently bond the polyfunctional amine and the polyfunctional carboxylic acid or the polyfunctional acid halide to the polyamide. Similarly, as for steps (A) and (B), it is preferable to carry out step (B) after step (A).
• steps (a) and (b) are preferably completed at step (b). This is because the removal performance and water permeability can be stabilized by modifying the amino group with a carboxy group.
• steps (A) and (B) are preferable to repeat steps (A) and (B) alternately two or more times, and it is preferable to complete the repetition of steps (A) and (B) at step (B).
• the polyfunctional amine aqueous solution, and the polyfunctional carboxylic acid aqueous solution or the polyfunctional acid halide solution can be brought into contact with the separation functional layer in a state in which the polyamide-based semipermeable membrane is incorporated in a semipermeable membrane element (sometimes simply referred to as an "element").
• a semipermeable membrane element sometimes simply referred to as an "element”
• These solutions may be continuously supplied to the element, or the semipermeable membrane may be immersed in these solutions by supplying the solution to the element and then leaving it to stand, or the element may be immersed in the solution.
• the solution can be brought into contact with the separation functional layer by flowing it through the supply side flow path of the semipermeable membrane in the element.
• the polyfunctional amine aqueous solution, the polyfunctional carboxylic acid aqueous solution, and the condensing agent may be supplied to the element simultaneously, or an aqueous solution containing only the condensing agent may be supplied to the semipermeable membrane element first, and then the polyfunctional amine aqueous solution or the polyfunctional carboxylic acid aqueous solution may be supplied.
• the contact time of the polyfunctional amine aqueous solution with the surface of the separation functional layer is preferably longer than the contact time of the polyfunctional carboxylic acid aqueous solution or the organic solvent solution containing a polyfunctional acid halide with the surface of the separation functional layer.
• the semipermeable membrane is incorporated into a semipermeable membrane element, and it is preferable to carry out the above steps (a) and (b) on a semipermeable membrane element that exhibits at least one of a salt permeability that is 10% or more higher than the initial value and a neutral molecule permeability that is 10% or more higher than the initial value.
• a salt permeability that is 10% or more higher than the initial value
• a neutral molecule permeability that is 10% or more higher than the initial value.
• the "initial value” refers to the salt permeability or neutral molecule permeability calculated from the standard salt rejection rate or standard neutral molecule rejection rate listed on the element's specification sheet.
• Neutral molecule permeability (%) 100 - Neutral molecule removal rate (%)
• the bonds in step (a) and step (b) are preferably both covalent bonds.
• bonding by covalent bonds it is possible to obtain bonds with high bonding strength, so that the membrane performance can be more stably maintained even after operation for a long time or contact with a chemical solution such as an acid or an alkali.
• a covalent bond for example, a condensing agent can be used, and in order to make the bond in step (b) a covalent bond, a condensing agent or a polyfunctional acid halide solution can be used. The same applies to steps (A) and (B).
• the condensing agent used in the above-mentioned step (a) and step (b), or step (A) and step (B), includes carbodiimide-based condensing agents such as N,N'-diisopropylcarbodiimide, N,N'-dicyclohexylcarbodiimide, 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide, and 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride (hereinafter, "EDC-HCl”), imidazole-based condensing agents such as N,N'-carbonyldiimidazole and 1,1'-carbonyldi(1,2,4-triazole), 4-(4,6-dimethoxy-1,3,5-triazin-2-yl)-4-methylmorpholinium chloride (hereinafter, "DMT-MM”), 3-(diethoxy)
• uronium condensing agents examples include uronium tetrafluoroborate, O-[2-oxo-1(2H)-pyridyl]-N,N,N',N'-tetramethyluronium tetrafluoroborate, ⁇ [(1-cyano-2-ethoxy-2-oxoethylidene)amino]oxy ⁇ -4-morpholinomethylene ⁇ dimethylammonium hexafluorophosphate, 2-chloro-1,3-dimethylimidazolinium hexafluorophosphate, 1-(chloro-1-pyrrolidinylmethylene)pyrrolidinium hexafluorophosphate, 2-fluoro-1,3-dimethylimidazolinium hexafluorophosphate, fluoro-N,N,N',N'-tetramethylformamidinium hexafluorophosphate, and sulfuric acid.
• carbodiimide-based or triazine-based condensing agents are preferred, and EDC-HCl is a carbodiimide-based condensing agent, and DMT-MM is a triazine-based condensing agent, which are preferred for condensation in aqueous systems.
• the polyfunctional amine aqueous solution, and the polyfunctional carboxylic acid aqueous solution or the organic solvent containing the polyfunctional acid halide may each contain a compound such as an acylation catalyst, a polar solvent, an acid scavenger, or an antioxidant, as necessary.
• Acids are mainly used to clean inorganic fouling (scale), including hydrochloric acid, nitric acid, sulfuric acid, citric acid, and oxalic acid.
• Alkalis are mainly used to clean organic fouling, including sodium hydroxide and potassium hydroxide.
• oxidizing agent such as chlorine
• examples of the oxidizing agent include hypochlorite, chlorinated isocyanurate, percarbonate, ozone, potassium permanganate, etc.
• the above-mentioned treatment method can be widely applied to semipermeable membranes having a separation functional layer containing polyamide (polyamide-based semipermeable membranes).
• the semipermeable membrane preferably has separation performance as a reverse osmosis membrane or a nanofiltration membrane.
• the semipermeable membrane may be used in the form of a composite membrane by further providing a support.
• the support may include a substrate and a porous support layer, or may be composed of only a porous support.
• the substrate is preferably a nonwoven fabric (including long fiber nonwoven fabric and short fiber nonwoven fabric) or a woven or knitted fabric.
• the substrate is composed of, for example, a polyester polymer, a polyamide polymer, a polyolefin polymer, or a mixture or copolymer thereof.
• Materials constituting the porous support layer include polysulfone, polyethersulfone, polyamide, polyester, cellulose polymer, vinyl polymer, polyphenylene sulfide, polyphenylene sulfide sulfone, polyphenylene sulfone, and polyphenylene oxide.
• examples of cellulose polymers include cellulose acetate and cellulose nitrate
• examples of vinyl polymers include polyethylene, polypropylene, polyvinyl chloride, and polyacrylonitrile.
• the separation functional layer preferably contains cross-linked aromatic polyamide as the main component.
• the main component means a component that accounts for 50% by mass or more of the components of the separation functional layer.
• the content of cross-linked aromatic polyamide in the separation functional layer is preferably 80% by mass or more, and more preferably 90% by mass or more.
• Crosslinked aromatic polyamide refers to a polymer of polyfunctional aromatic amines and polyfunctional aromatic acid chlorides.
• the compounds listed for steps (a) and (b) of the above-mentioned treatment method are preferably used.
• the separation functional layer is preferably formed by interfacial polymerization using an aqueous solution containing a polyfunctional aromatic amine and an organic solvent solution containing a polyfunctional aromatic acid chloride.
• the interfacial polymerization process includes (i) applying an aqueous solution containing a polyfunctional aromatic amine to a support (or to the porous support layer if the support has a substrate and a porous support layer), and (ii) applying an organic solvent solution containing a polyfunctional aromatic acid chloride to the support after the above process (i) (or to the porous support layer if the support has a substrate and a porous support layer).
• steps (i) and (ii) examples of application methods include immersion, showering, and coating.
• step (ii) the solvents listed in step (b) of the above-mentioned treatment method are preferably used.
• the semipermeable membrane is wound around a cylindrical water collection pipe having a large number of holes, together with a feed-side passage material such as a plastic net, a permeate-side passage material such as a tricot, and, if necessary, a film for increasing pressure resistance, and is suitably used as a spiral-type semipermeable membrane element. Furthermore, this element can be connected in series or in parallel and housed in a pressure vessel to form a semipermeable membrane module.
• semipermeable membranes, their elements, and modules can be combined with pumps that supply feed water to them, and equipment that pretreats the feed water, to form a fluid separation device.
• the feed water can be separated into permeated water, such as drinking water, and concentrated water that did not pass through the membrane, allowing water suitable for the intended purpose to be obtained.
• the semipermeable membrane element treatment device includes a first tank for storing an aqueous solution containing a polyfunctional amine, a second tank for storing at least one of an aqueous solution containing a polyfunctional carboxylic acid and an organic solvent solution containing a polyfunctional acid halide, an element mounting part for mounting a semipermeable membrane element incorporating at least one semipermeable membrane having a separation functional layer containing polyamide, a pipe connecting the first tank and the element mounting part, a pipe connecting the second tank and the element mounting part, a first pump between the first tank and the element mounting part, and a second pump between the second tank and the element mounting part.
• the semipermeable membrane element treatment device includes a semipermeable membrane unit including a container in which a semipermeable membrane element is loaded as the element mounting part, pipes connecting the semipermeable membrane unit and each tank, and a pump connected to the pipes.
• the pipes connecting the first tank and the second tank with the semipermeable membrane element are preferably connected so that each solution is supplied from the separating functional layer side of the semipermeable membrane.
• the processing equipment may further include tanks, pumps, and piping for cleaning solutions.
• the polyamide-based semipermeable membrane treated by the treatment method of the present invention is a semipermeable membrane whose removal performance does not reach the desired level or whose removal performance has decreased.
• steps (a) and (b), or steps (A) and (B) are performed on a semipermeable membrane that has been subjected to the above-mentioned cleaning treatment, specifically a semipermeable membrane that has been contacted with at least one agent selected from the group consisting of an acid having a pH of 4 or less, an alkali having a pH of 10 or more, and an oxidizing agent, the removal performance can be improved.
• the present invention also provides a method for improving the removal performance of a polyamide-based semipermeable membrane.
• the present invention also provides a method for producing a semipermeable membrane element, which includes a step of treating a polyamide-based semipermeable membrane with a treatment method including the above-mentioned steps (a) and (b), or steps (A) and (B).
• the semipermeable membrane elements obtained by the above-mentioned manufacturing method are connected in series or parallel and housed in a pressure vessel to be used as a semipermeable membrane module.
• the semipermeable membrane elements and semipermeable membrane modules can be combined with a pump that supplies a fluid to them, a device that pretreats the fluid, and the like to form a fluid treatment device.
• the fluid treatment method of the present invention uses a semipermeable membrane element obtained by the above-mentioned manufacturing method to treat a fluid, and is suitable for treating, for example, water containing salt or harmful substances, industrial wastewater, domestic wastewater, etc.
• Membrane Permeation Flux Seawater adjusted to pH 6.5 (TDS concentration 3.5%, boron concentration approximately 5 ppm) was supplied to the element at an operating pressure of 5.5 MPa and a recovery rate of 8%, and membrane filtration was carried out for 24 hours.
• the amount of water that passed through the membrane after that was expressed as the membrane permeation flux ( m3 / m2 /day) in terms of the amount of water that passed through (cubic meters) per square meter of membrane surface per day.
• Membrane permeation flux ratio (Membrane permeation flux ratio, salt (TDS) permeation rate ratio, boron permeation rate ratio)
• the membrane permeation flux ratio, salt (TDS) permeation rate ratio, and boron permeation rate ratio were calculated from the following formulas.
• Reference Example 3 As in Reference Example 2, a reverse osmosis membrane element for seawater desalination TM810V manufactured by Toray Industries, Inc. was subjected to accelerated membrane deterioration treatment using acid and alkali, and then further subjected to accelerated membrane deterioration treatment by supplying an aqueous solution containing sodium hypochlorite adjusted to a chlorine concentration of 100 ppm at 25° C. for 24 hours. Thereafter, the performance of the element was evaluated.
• Example 1 An aqueous solution containing 0.05% by mass of m-phenylenediamine and 0.10% by mass of DMT-MM was supplied to the accelerated deteriorated semipermeable membrane element obtained in Reference Example 2 for 1.5 hours at 25° C., and then an aqueous solution containing 0.05% by mass of trimesic acid and 0.10% by mass of DMT-MM was supplied to the semipermeable membrane element for 1.5 hours at 25° C. After performance evaluation of the semipermeable membrane element after the treatment, an acid immersion test or alkali immersion test was carried out, and the performance of the semipermeable membrane element was evaluated again.
• Example 2 Except for supplying the m-phenylenediamine aqueous solution and the trimesic acid aqueous solution twice each, the treatment was carried out in the same manner as in Example 1. After evaluating the performance of the semipermeable membrane element after the treatment, an acid immersion test or an alkali immersion test was carried out, and the performance of the semipermeable membrane element was evaluated again. By repeating the treatment twice, the performance of the semipermeable membrane element after the treatment was further improved compared to Example 1.
• Example 3 Except for the fact that the m-phenylenediamine aqueous solution and the trimesic acid aqueous solution were each supplied three times, the treatment was carried out in the same manner as in Example 1. After the performance evaluation of the semipermeable membrane element after the treatment, an acid immersion test or an alkali immersion test was carried out, and the performance of the semipermeable membrane element was evaluated again. By repeating the treatment three times, the performance of the semipermeable membrane element after the treatment was further improved compared to Example 2, and was improved to nearly the performance of Reference Example 1.
• Example 4 Except for switching the supply order of the m-phenylenediamine aqueous solution and the trimesic acid aqueous solution, each of them was supplied three times, the same treatment as in Example 1 was carried out. After the performance evaluation of the semipermeable membrane element after the treatment, an acid immersion test or an alkali immersion test was carried out, and the performance evaluation of the semipermeable membrane element was carried out again. When the treatment was carried out in the order of step (b) and then step (a), the performance improvement effect was lower than in Example 3.
• Example 5 Except for alternately feeding the m-phenylenediamine aqueous solution and the trimesic acid aqueous solution twice, and then feeding the m-phenylenediamine aqueous solution, the treatment was carried out in the same manner as in Example 1. After evaluating the performance of the semipermeable membrane element after the treatment, an acid immersion test or an alkali immersion test was carried out, and the performance of the semipermeable membrane element was evaluated again. The performance of the semipermeable membrane element was sufficiently improved by the treatment, but since the polyamide terminal was an amino group, the performance deterioration after acid immersion or alkali immersion was greater than in Examples 2 and 3 in which the polyamide terminal was a carboxy group.
• Example 6 Treatment was carried out in the same manner as in Example 1, except that the supply order of m-phenylenediamine and the aqueous trimesic acid solution was reversed and the supply was carried out twice, and then the aqueous trimesic acid solution was supplied. After the performance evaluation of the semipermeable membrane element after the treatment, an acid immersion test or an alkali immersion test was carried out, and the performance evaluation of the semipermeable membrane element was carried out again. The performance improvement effect was lower than in Example 4, but since the polyamide terminal was a carboxy group, the performance deterioration after acid immersion or alkali immersion was lower than in Example 4.
• Example 7 Treatment was carried out in the same manner as in Example 3, except that a decane solution containing 0.05 mass% trimesoyl chloride was supplied for 1.5 hours at 25° C. instead of an aqueous solution containing 0.05 mass% trimesic acid and 0.10 mass% DMT-MM. After performance evaluation of the semipermeable membrane element after treatment, an acid immersion test or alkali immersion test was carried out, and the performance of the semipermeable membrane element was evaluated again. Even when a decane solution containing trimesoyl chloride was used instead of an aqueous solution containing trimesic acid and DMT-MM, the performance of the semipermeable membrane element after treatment was improved as in Example 3.
• Example 8 Treatment was carried out in the same manner as in Example 3, except that the semipermeable membrane element obtained in Reference Example 3 that had been subjected to accelerated deterioration was used. After performance evaluation of the treated semipermeable membrane element, an acid immersion test or an alkali immersion test was carried out, and performance evaluation of the semipermeable membrane element was carried out again. For semipermeable membrane elements that had further progressed in deterioration, the performance improvement effect was insufficient under these treatment conditions.
• Example 9 Except for doubling the concentrations of m-phenylenediamine, trimesic acid, and DMT-MM, the treatment was carried out in the same manner as in Example 8. After evaluating the performance of the semipermeable membrane element after the treatment, an acid immersion test or an alkali immersion test was carried out, and the performance of the semipermeable membrane element was evaluated again. By doubling the supply concentration in each treatment, the reaction rate in each treatment increased, and the performance of the semipermeable membrane element after the treatment was improved compared to Example 8.
• Example 10 Except for changing the supply time of each treatment to 4 hours, the treatment was performed in the same manner as in Example 8. After the performance evaluation of the semipermeable membrane element after the treatment, an acid immersion test or an alkali immersion test was carried out, and the performance of the semipermeable membrane element was evaluated again. By changing the supply time of each treatment to 4 hours, the reaction rate in each treatment was increased, and the performance of the semipermeable membrane element after the treatment was improved compared to Example 8.
• Example 11 Except for changing the supply temperature for each treatment to 40° C., the treatments were carried out in the same manner as in Example 8. After evaluating the performance of the semipermeable membrane element after the treatment, an acid immersion test or an alkali immersion test was carried out, and the performance of the semipermeable membrane element was evaluated again. By changing the supply temperature for each treatment to 40° C., the reaction rate in each treatment was increased, and the performance of the semipermeable membrane element after the treatment was improved compared to Example 8.
• Example 12 The treatments were carried out in the same manner as in Example 8, except that the supply time for each treatment was changed to 4 hours and the supply temperature to 40°C. After the performance evaluation of the semipermeable membrane element after the treatment, an acid immersion test or an alkali immersion test was carried out, and the performance of the semipermeable membrane element was evaluated again. By doubling the supply concentration for each treatment, changing the supply time to 4 hours, and changing the supply temperature to 40°C, the reaction rate in each treatment increased, and the performance of the semipermeable membrane element after the treatment was greatly improved compared to Example 8, and was improved to nearly the performance of Reference Example 1.
• Example 1 to 12 and Comparative Examples 1 and 2 The treatment methods of Examples 1 to 12 and Comparative Examples 1 and 2 are shown in Table 1.
• the properties of the semipermeable membrane elements obtained in Reference Examples 1 to 3 are shown in Table 2.
• the performance of the semipermeable membrane elements obtained in Reference Example 1, Examples 1 to 12, and Comparative Examples 1 and 2 are shown in Table 3.
• the performance of the semipermeable membrane element to which the treatment method according to this embodiment was applied was close to the initial performance before accelerated deterioration, and it was found that an excellent performance improvement effect was obtained in a short period of time.

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• 2023
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