JP2018058040A - Regeneration method of separation membrane module - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for regenerating a composite membrane module reduced in performance by chemical cleaning of using sodium hypochlorite, an acid and alkali.SOLUTION: In a regeneration method of a membrane module of incorporating a composite membrane having a first separation layer constituted of an anionic polymer on one surface of a porous support membrane and having a second separation layer constituted of at least one kind of more cationic or anionic ionomers on a surface of the first separation layer, the regeneration method of the membrane module executes a process of contacting at least one kind or more cationic polymer solutions or anionic polymer solutions with the separation layer side of the composite membrane and a process of contacting a crosslinking agent solution in order.SELECTED DRAWING: None

Description

  The present invention relates to a method for regenerating a separation membrane module whose performance has deteriorated due to chemical membrane cleaning using sodium hypochlorite, acid solution, alkaline solution, or the like, and in particular, replenishes a polymer constituting the separation layer. Thus, the separation membrane module regeneration method is characterized in that the separation membrane is repaired in situ within the module.

  Water treatment by membrane separation, particularly water treatment using modules composed of reverse osmosis (RO) membrane or nanofiltration (NF) membrane, NF membrane as well as separation of polymers, colloids and inorganic particles In the module, low molecular weight of 1000 to 200 molecular weight, and in the RO membrane module, the molecular weight of 200 or less, further low molecular weight of 100 or less can be highly separated, and monovalent ions or multivalent ions can also be separated. It has the feature of being. Moreover, it has the advantage that it is energy saving compared with distillation separation, and does not accompany the deterioration and modification | denaturation of the solute by heat. Therefore, RO and NF membrane modules are used in fruit juice concentration processes, food processes such as beer enzyme separation, drinking water by desalination of seawater and brine, production of ultrapure water, production of sterile water for medical use, and valuable materials from wastewater. Has been established as an indispensable separation process.

  In the filtration operation of the separation membrane module, membrane fouling occurs due to various organic substances, inorganic salts, inorganic particles, and the like. Since the membrane in which fouling has occurred has a reduced water permeability, the filtration operation efficiency is significantly reduced. As a method of removing fouling substances, physical washing such as flushing and back pressure washing is usually performed, but it is not possible to completely remove fouling substances firmly attached to the membrane surface by physical washing only by long-term filtration operation. difficult. Therefore, various types of chemical cleaning with sodium hypochlorite, acid, alkali, etc. are used in combination.

  However, the performance of the separation membrane module exposed to the chemical solution for a long period of time is inevitably deteriorated because the separation layer is chemically degraded. In order to extend the lifetime of the module, various module performance recovery means have been studied so far.

  Patent Document 1 discloses that a reverse osmosis membrane module, a reverse osmosis membrane module having a cross-linked polyamide separation layer as a first means, an organic solvent containing a polyfunctional acid halide or polyfunctional isocyanate as a constituent component of the cross-linked polyamide is reverse osmosis. A method of trying to regenerate the polyamide separation layer by contacting the skin layer of the membrane is disclosed, and as a second means, a solution of a water-insoluble polymer (for example, polyvinyl alcohol having a high saponification degree) is used as the skin of the reverse osmosis membrane. A method of contacting a layer is disclosed.

  Patent Document 2 discloses a method for improving or recovering the performance of a separation membrane by allowing polyphenols such as tannin to pass through the separation membrane module under pressure.

  However, the performance recovery means such as a polyamide membrane as the first means of Patent Document 1 recovers the performance by reacting the amide group remaining in the polyamide separation layer in the module with an acid halide. It is less effective for polyamide membranes whose performance has been greatly degraded by sodium chlorate, and the number of times the regeneration treatment is applied is limited. Furthermore, heptane, hexane, or the like is used as the organic solvent that can dissolve acid halide, and therefore, it is not suitable for in-situ regeneration treatment in a membrane filtration facility, such as requiring careful washing treatment after module regeneration treatment.

  In addition, the method of polymer coating by bringing the organic polymer solution into contact with the skin layer of the reverse osmosis membrane as in the second means of Patent Document 1 makes it difficult to control the thickness of the coat layer, and performs performance recovery with good reproducibility. Has the problem of being difficult. In particular, in an external pressure filtration type hollow fiber membrane module, a large number of yarn bundles in the module are entangled, and the contact area between the yarns is large. Therefore, when such a method is used, a uniform coat layer cannot be formed. In addition, there is a problem that the yarns adhere to each other with a polymer.

  The method in which the polyphenol solution of Patent Document 2 is pressurized and passed through the module is a kind of membrane performance recovery means by fouling in which polymers are deposited on the surface of the separation layer. For separation membranes with significantly reduced separability, it is difficult to obtain a performance recovery effect. In addition, there is a problem that the membrane performance is not stable in the long term because physical or chemical bonding is not performed between the molecules of the polyphenols or between the separation layer and the molecules of the polyphenols.

JP-A-11-104470 JP 2006-224048 A

  The present invention has been made in view of such problems of the prior art, and its purpose is to perform chemical membrane cleaning using sodium hypochlorite, acids, alkalis, etc., in a module having a specific separation membrane configuration. The present invention provides a means for significantly recovering the film performance reduced by reproducibility with good reproducibility.

  As a result of intensive studies to achieve the above object, the present inventor has completed a method for regenerating a separation membrane module based on the following knowledge.

  In the present invention, the target separation membrane module has a first separation layer made of a polymer having an anionic functional group on the surface of the porous support membrane, and at least one kind of cation on the outer surface of the first separation layer. Module comprising a separation membrane having a second separation layer formed by crosslinking a functional polymer or an anionic polymer.

  The inventor contacts the separation membrane module with an aqueous solution of a cationic polymer or an anionic polymer on the separation layer side of the separation membrane whose performance has deteriorated due to exposure to sodium hypochlorite or the like, and then further crosslinks. It has been surprisingly found that the separation performance of the separation membrane module is remarkably recovered when the agent solution is filled and the cationic polymer or the anionic polymer is crosslinked. Furthermore, when the exposure test of sodium hypochlorite was continued and the regeneration treatment was carried out, it was found that the performance recovered again.

  The reason for this is that, in the composite membrane that is the subject of the present invention, the pore diameter of the separation layer and partial peeling due to oxidative degradation due to sodium hypochlorite are mainly the polymer cross-linked product of the outermost layer of the separation membrane. 2 separate layers. Therefore, it is considered that the degree of deterioration of the first separation layer containing the anionic functional group in the inner layer is relatively small. Therefore, by bringing the degraded module into contact with a cationic polymer aqueous solution, an anionic polymer aqueous solution and a cross-linking agent solution in sequence, the polymer adsorption and cross-linking treatment via electrostatic interaction is performed again, thereby realizing performance recovery. It is thought that.

This invention is completed based on said knowledge, and has the structure of the following (1)-(4).
(1) It has a first separation layer composed of an anionic polymer on one surface of the porous support membrane, and the surface of the first separation layer is composed of at least one kind of cationic or anionic polymer. A method for regenerating a membrane module incorporating a composite membrane having a second separation layer, the step of bringing at least one cationic polymer solution or an anionic polymer solution into contact with the separation layer side of the composite membrane, cross-linking A method for regenerating a membrane module, wherein the step of bringing the agent solution into contact is sequentially performed.
(2) The method according to 1, wherein the cationic polymer solution is a cationic polyvinyl alcohol aqueous solution.
(3) The method according to 1 or 2, wherein the anionic polymer solution is an aqueous anionic polyvinyl alcohol solution.
(4) The method according to any one of 1 to 3, wherein the crosslinking agent solution is an aqueous solution of aldehydes.
(5) The method according to any one of claims 1 to 4, wherein the step of contacting the cationic polymer solution or the anionic polymer solution and the step of contacting the crosslinking agent solution are repeated twice or more in order.

  The present invention has a first separation layer made of a polymer containing an anionic functional group on the surface of a porous support membrane, and at least one kind of cationic functional group or anionic functional group on the surface of the first separation layer. In a module having a specific composite membrane structure having a second separation layer made of a crosslinked product of a polymer containing a polymer, the membrane solution is brought into contact with an aqueous solution of the polymer and a crosslinking agent solution against the composite membrane module whose performance has deteriorated It is possible to easily and significantly recover the performance. Therefore, the lifetime of the composite membrane module can be further extended, which is economical.

It is the figure which showed the change of the removal rate of the separation membrane after the sodium hypochlorite exposure process of the composite membrane module and the regeneration process of this invention. It is the figure which showed the water permeability change of the separation membrane after the sodium hypochlorite exposure process of a composite membrane module and the regeneration process of this invention. It is a schematic explanatory drawing which shows an example of embodiment in the hollow fiber membrane module of this invention.

  The structure of the composite membrane to be subjected to the separation membrane module regeneration method of the present invention has a specific configuration: a first separation layer on the surface of the porous support membrane, and a second separation layer on the outer surface thereof. is there.

  The first separation layer provided on the outer surface of the porous support membrane is composed of a polymer having an anionic functional group, and is particularly preferably composed of a polymer having a sulfonic acid group, a carboxyl group, or a phosphonic acid group. More preferably, it is preferably composed of a polymer having a sulfonic acid group (sulfonated polymer) from the viewpoint of production and availability. Specifically, sulfonated polysulfone, sulfonated polyimide, sulfonated polyarylene ether, sulfonated polysulfone, sulfonated polyphenylene ether (sulfonated polyphenylene oxide), sulfonated polyetherimide, sulfonated polyether ether ketone, sulfonated polyphenylene It is preferably composed of sulfide, sulfonated polybenzimidazole or the like. These polymers have a high density of sulfonic acid groups while maintaining the mechanical strength of the first separation layer.

  The sulfonated polymer is obtained by sulfonating a known polymer such as polyphenylene ether (polyphenylene oxide), polyimide, polysulfone, polyethersulfone, polyetherimide, etc. using chlorosulfuric acid or concentrated sulfuric acid. Is preferred. More preferable examples include a sulfonated polymer obtained by copolymerizing a hydrophilic monomer having a sulfonic acid group and a hydrophobic monomer having no sulfonic acid group. Such a copolymerized sulfonated polymer can precisely control the amount of sulfonic acid groups introduced with good reproducibility, and by selecting a desired monomer, it has an excellent mechanical property while having a high sulfonic acid group density. It is preferable because of its strength and high chemical resistance.

As the copolymerized sulfonated polymer, a sulfonated polyarylene having a polymer composed of a repeating structure of a hydrophobic segment represented by the following formula (IV) and a hydrophilic segment represented by the following formula (V) as a basic skeleton: Ether (SPAE) is preferred. Such a polymer exhibits a rigid molecular skeleton and excellent chemical durability, and is excellent in mechanical strength.


In the above formula, X is any of the following:

Y is one of the following:

Z is one of the following:

W is one of the following:

The same Y and W are not selected,
a and b each represent a natural number of 1 or more;
R ¹ and R ² represent —SO ₃ M or —SO ₃ H, M represents a metal element,
Sulfonation rate expressed as a percentage of the number of repetitions of formula (V) to the total number of repetitions of formula (IV) and formula (V) in the sulfonated polyarylene ether copolymer is from 5% Is larger than 80%.

Furthermore, the copolymerized sulfonated polymer having higher mechanical strength and high flexibility and chemical durability includes a hydrophobic segment represented by the following formula (I) and a hydrophilic property represented by the following formula (II). A sulfonated polyarylene ether having a repeating structure of segments is preferred.


In the above formula, m and n each represent a natural number of 1 or more, R ¹ and R ² represent —SO ₃ M or —SO ₃ H, M represents a metal element, and in the sulfonated polyarylene ether copolymer The sulfonation rate expressed as a percentage of the number of repetitions of formula (II) to the sum of the number of repetitions of formula (I) and (II) is greater than 5% and less than 80%.

  The preferred ion exchange capacity IEC for the degree of sulfonation of the polymer (ie, milliequivalents of sulfonic acid groups per gram of sulfonated polymer) is 0.5-3.0 meq. / G, and the preferred range of sulfonation rate DS is greater than 5% and less than 80%. When IEC and DS are lower than the above ranges, the anionic charge density on the surface of the first separation layer becomes small because there are too few sulfonic acid groups. Therefore, there is a tendency that the formation process of the second separation layer by the alternating lamination method described later does not proceed uniformly, which is not preferable. Moreover, when IEC and DS are higher than the said range, since the hydrophilic property of a polymer becomes large too much and a 1st separated layer will swell excessively, it is unpreferable. A more preferable range of IEC is 0.7 to 2.9 meq. / G, and a more preferable sulfonation rate DS range is 10% to 70%.

  The porous support membrane is a polymer selected from known solution-forming polymers such as polyphenylene ether (polyphenylene oxide), polysulfone, polyethersulfone, polyetherimide, polyketone, polyimide, polyacrylonitrile, polystyrene, and polyvinylidene fluoride. Asymmetric membrane. In particular, as disclosed in WO2014 / 054346, aprotic polar solvents (dimethyl sulfoxide, N-methyl-2-pyrrolidone, which can dissolve certain SPAE (I) (II) and (IV) (V), It is preferably an asymmetric membrane of polyphenylene ether that is insoluble in dimethylacetamide, dimethylformamide, γ-butyrolactone, and the like. Since the polyphenylene ether porous support membrane shows insolubility or limited solubility in the solvent, a composite membrane can be easily obtained by using the above-mentioned SPAE by a known polymer coating method.

The polyphenylene ether has a structure represented by the following formula (III).

In the above formula (III), k represents a natural number of 1 or more.

  As a method of combining the first separation layer with the porous support membrane, a known method can be used, and specifically, an application method such as a coating method or a spray method can be used. From the viewpoint of obtaining a high-quality separation layer stably and simply, a coating method is preferred.

  The composite membrane having the first separation layer composed of the sulfonated polymer preferably has a NaCl rejection of 60% or less for the purpose of having sufficient mechanical strength and increasing water permeability. Depending on the manufacturing conditions, it is possible to impart sufficient separability, but the water permeability is significantly impaired, and as a result of the dense separation layer, defects on the membrane surface due to friction tend to occur. It is not preferable. The NaCl rejection is more preferably 30% or less. More preferably, it is 20% or less. However, the measurement conditions for the NaCl rejection are 0.5 MPa (5 bar), a NaCl concentration of 1500 ppm, and a recovery rate of about 5%.

  The thickness of the first separation layer is preferably 50 nm or more and 10 μm or less. If the thickness is too small, it is not preferable because the effect of oxidative deterioration such as sodium hypochlorite tends to occur. When the thickness is too large, the permeation resistance becomes too large and sufficient water permeability cannot be obtained. More preferably, it is 100 nm or more and 1 μm or less.

  A known structure can be adopted for the composite membrane module. Preferably, a spiral type module using a flat membrane and a hollow fiber membrane module in which hollow fiber membranes are bundled can be employed. Similarly, as the form of the separation membrane, an external pressure filtration type hollow fiber membrane, an internal pressure filtration type hollow fiber membrane, and a flat membrane can be adopted as desired.

  Next, a method for forming the second separation layer will be described. The second separation layer can be formed by a method (Layer-by-Layer method) in which a cationic polymer and an anionic polymer are alternately laminated starting from the first separation layer having an anionic surface.

  In the present invention, the cationic polymer is preferably a modified polyvinyl alcohol having a cationic functional group. The anionic polymer is preferably a modified polyvinyl alcohol having an anionic functional group.

  First, an aqueous solution of modified polyvinyl alcohol (cationic polyvinyl alcohol) having a cationic functional group is filled into the composite membrane module containing water. A CPVA adsorption treatment is performed by bringing a cationic polyvinyl alcohol (hereinafter abbreviated as CPVA) solution into contact with the anionic surface of the first separation layer in the module for a certain period of time. From the viewpoint of forming a thin separation layer without defects, the solution is preferably kept in contact for a period of 10 seconds to 10 hours. More preferably, it is 1 minute or more and 3 hours or less. Thereafter, the CPVA aqueous solution is extracted and rinsed with pure water. Preferably, rinsing is performed for 10 seconds or more to remove excess polymer other than CPVA adsorbed on the membrane from the module.

  Thereafter, preferably, an aqueous solution of a modified polyvinyl alcohol having an anionic functional group (hereinafter sometimes abbreviated as anionic polyvinyl alcohol or APVA) is filled, and an adsorption layer of an APVA layer is further formed on the surface of the adsorption layer of CPVA. Let The adsorption time and the pure water rinse treatment may be performed by the same method.

  The above-described adsorption treatment of CPVA and APVA can be alternately repeated starting from the anionic first separation layer. It is preferable to perform at least one CPVA adsorption. More preferably, APVA adsorption is added to CPVA adsorption because an effect of improving separation performance is observed. It is also preferable to perform the adsorption treatment twice or more.

  The concentrations of the CPVA and APVA aqueous solutions are each preferably 0.01% by mass to 1% by mass. When the concentration is smaller than this range, the adsorption is not sufficiently performed and the film performance is deteriorated. If the concentration is too high, the adsorption layer tends to be too thick, and the viscosity of the aqueous solution becomes high.

  The solvent of the CPVA and APVA aqueous solutions is preferably pure water, and it is preferable to use pure water having a conductivity of preferably 10 μS / cm or less, more preferably 1 μS / cm or less. If the conductivity of water as a solvent is too high, the adsorption of the modified PVA to the first separation layer via electrostatic interaction tends to be hindered due to the influence of Coulomb shielding as described above.

  After the adsorption treatment of CPVA and APVA, it is preferable to acetal crosslink the hydroxyl groups of CPVA and APVA by filling the module with an aqueous solution of aldehydes. An adsorbed layer of modified polyvinyl alcohol (PVA) that is not subjected to cross-linking has almost no separability. Only after the crosslinking treatment can the separation performance of the RO and NF membranes with a molecular weight cut off of 100 to 1000 be achieved. Surprisingly, such a cross-linked adsorption layer is formed to be extremely uniform and thin as compared with a PVA separation layer formed by a conventional coating method or the like, so that both high water permeability can be achieved. .

  As the aldehyde as the crosslinking agent, for example, formaldehyde, glutaraldehyde, glyoxal, benzaldehyde, orthophthalaldehyde, isophthalaldehyde, terephthalaldehyde and the like can be preferably used. More preferably, glutaraldehyde or orthophthalaldehyde can be used in terms of high water solubility, relatively low toxicity, and good separation membrane performance after the crosslinking treatment.

  The aqueous solution concentration of the aldehyde crosslinking agent is preferably 0.01% by mass to 20% by mass. Under a concentration condition lower than this range, crosslinking of the hydroxyl group of polyvinyl alcohol does not proceed sufficiently. The crosslinking reaction proceeds even under a concentration condition higher than this range, but this is not preferable because the toxicity of the solution becomes high and handling becomes difficult. More preferably, it is the range of 0.1 mass%-5 mass%.

  In the crosslinking treatment, the crosslinking time is preferably 10 minutes or longer and 40 hours or shorter. When the crosslinking time is too short, the blocking performance of the second separation layer is small. In addition, if the crosslinking time is too long, there is not much effect. From the viewpoint of promoting the crosslinking reaction, it is also preferable to maintain the temperature of the aldehyde aqueous solution at 20 ° C. or more and 60 ° C. or less.

  After the crosslinking treatment, the inside of the module is sufficiently washed with pure water. From the viewpoint of completely removing aldehydes in the membrane, it is preferable to enhance the cleaning effect by performing a cross flow operation using pure water under a pressure of about 1 to 10 atm. Furthermore, when a cross-linking agent with a slightly low water solubility and strong hydrophobicity, such as orthophthalaldehyde, is used, the cross-linking agent tends to remain in the membrane. For example, a sodium hydrogen sulfite aqueous solution is filled in the module. In addition, an aldehyde and an adduct can be formed to enhance the cleaning effect. Or, for example, under alkaline conditions of pH 9 or higher, an aqueous solution of reducing sugar (glucose, fructose, glucosamine, etc.) having reducibility is filled in the module, and unreacted aldehyde groups and reducing sugars outside and inside the membrane are removed. A process of reacting and detoxifying can also be used.

  Thus, it is preferable that the module which has been subjected to the crosslinking treatment with aldehydes and sufficiently washed with water is again subjected to the adsorption treatment of CPVA and APVA and the aldehyde crosslinking by the same method. By repeating this adsorption / crosslinking treatment cycle, high separation performance (for example, a magnesium sulfate rejection of 95% or more and a molecular weight cut off of 100 to 300) can be obtained. Preferably, the adsorption / crosslinking treatment cycle is repeated twice or more.

  The thickness of the second separation layer is preferably 1 nm or more and 200 nm or less. When the thickness is too thin, the adsorption of the modified PVA is insufficient and the separability is not sufficiently developed. On the other hand, if it is too thick, the permeation resistance becomes too large and sufficient water permeability cannot be obtained. More preferably, it is 5 nm or more and 100 nm or less.

  The configuration of the modified PVA constituting the second separation layer will be described below.

  Although it does not specifically limit about the kind of cationic functional group contained in CPVA, It is preferable to have a 1-4 quaternary ammonium group, and a quaternary ammonium group is especially preferable from a viewpoint which has chemical durability and antibacterial property. Specifically, CPVA is saponified by copolymerizing a quaternary ammonium salt such as diallyldimethylammonium chloride and 3-methacrylamideamidopropyltrimethylammonium chloride with vinyl acetate as an unsaturated monomer having a cationic group. It is preferable that it is a polymer obtained by processing.

  Further, as another method for obtaining CPVA, a method in which a quaternary ammonium salt having a glycidyl group is added to a hydroxyl group of ordinary unmodified polyvinyl alcohol under an alkaline condition is also preferable. As the monomer having a glycidyl group, for example, glycidyltrimethylammonium chloride can be preferably used. Both the modification of polyvinyl alcohol by such an addition reaction and the modification by the above copolymerization can be preferably used. Moreover, both methods may be implemented to introduce two or more types of cationic groups into the polymer.

  On the other hand, for APVA, the type of anionic functional group is not particularly limited, and PVA having a sulfonic acid group, a phosphonic acid group, a carboxyl group, or the like can be used. From the viewpoint of easy production and availability, PVA having a sulfonic acid group is preferably used. For example, sulfonated PVA obtained by copolymerizing 2-acrylamido-2-methylpropane sulfonate and vinyl acetate and saponifying can be used. Similar to CPVA, two or more types of anionic groups may be introduced into the polymer.

  The amount of the cation group or anion group of CPVA and APVA is preferably at least 0.01 mol% to 30 mol%. More preferably, they are 0.1 mol% or more and 20 mol% or less. When the ionic functional group is smaller than this range, the adsorption to the hollow fiber membrane surface does not proceed sufficiently and the membrane performance is lowered, which is not preferable. On the other hand, if it is larger than this range, the second separation layer swells too much and the separation performance is lowered, which is not preferable.

  The degree of saponification of CPVA and APVA is preferably 60 to 99 mol%, more preferably 70 to 95 mol%, still more preferably 75 to 90 mol%. If the degree of saponification is larger than this range, the dispersibility of the modified PVA molecules in an aqueous solution tends to deteriorate, which is not preferable. When the degree of saponification is lower than this range, the stability of the aqueous solution is similarly deteriorated, which is not preferable. As such CPVA, K434 (degree of saponification 85.5-88.0, Nippon Synthetic Chemical Co., Ltd.), C-506 (degree of saponification 74.0-79.0, Kuraray), CM-318 (saponification) Degree 86.0-91.0, Kuraray Co., Ltd.). Moreover, as APVA, L-3266 (saponification degree 86.5-89.0, Nippon Synthetic Chemical Co., Ltd.), CKS50 (saponification degree 99.0 or more, Nippon Synthetic Chemical Co., Ltd.), AP-17 (saponification degree). 88 to 90, Nippon Vinegar Pover Co., Ltd.), AT-17 (degree of saponification 92 to 95, Nihon Venture Bi Pover Co., Ltd.), AF-17 (degree of saponification of 96.5 or more, Nippon Vinegar Pover Co., Ltd.) Etc.

  The membrane module deteriorated by the chemical cleaning using sodium hypochlorite or the like as described above can be reprocessed as it is, so that the regeneration process can be performed and the membrane performance can be recovered. .

  As a pretreatment for the regeneration treatment, it is preferable to sufficiently remove the fouling substance and the like by treatment with acid, alkali, ozone, sodium hypochlorite and the like.

  In the present invention, as a first aspect of the regeneration treatment, at least one kind of cationic polymer solution on the separation layer side of the composite membrane in the membrane module deteriorated by chemical cleaning using the sodium hypochlorite or the like or It is preferable to sequentially perform the step of bringing the anionic polymer solution into contact with and the step of bringing the crosslinking agent solution into contact. Further, as a second aspect, a step of bringing at least one kind of cationic polymer solution into contact with the separation layer side of the composite membrane in the membrane module, a step of bringing at least one kind of anionic polymer solution into contact, a crosslinking agent It is also included in the present invention that the step of bringing the solution into contact is sequentially performed. Furthermore, it is within the scope of the present invention to repeat the first aspect or the second aspect two or more times.

  Hereinafter, the effects of the present invention will be specifically described by way of examples, but the present invention is not limited thereto.

(Preparation of hollow fiber support membrane)
As a polymer for the hollow fiber support membrane, polyphenylene ether PX100L (hereinafter abbreviated as PPE) manufactured by Mitsubishi Engineering Plastics Co., Ltd. was prepared. N-methyl-2-pyrrolidone (hereinafter abbreviated as NMP) was added and kneaded at 130 ° C. so that the PPE would be 20% by mass to obtain a uniform film forming stock solution.

  Subsequently, while extruding the film-forming stock solution into a hollow shape from a double cylindrical tube nozzle, a 35% by mass NMP aqueous solution was simultaneously extruded as an internal solution to be molded, and was allowed to dry in the air at room temperature. Then, it was immersed in 30 mass% NMP aqueous solution (coagulation bath) at 30 degreeC, and after producing the PPE hollow fiber support membrane, it washed with water.

The obtained PPE hollow fiber support membrane had an outer diameter of 250 μm and a film thickness of 50 μm. When the pure water permeation test was performed, the water permeation amount was 43 L / (m ² · h · bar).

(Formation of first separation layer)
An SPAE having a repeating structure of the hydrophobic segment represented by the above formula (I) and the hydrophilic segment represented by the above formula (II) was prepared as follows.

  3,3'-disulfo-4,4'-dichlorodiphenylsulfone disodium salt (hereinafter abbreviated as S-DCDPS) 3.0000 kg, 2,6-dichlorobenzonitrile (hereinafter abbreviated as DCBN) 1.7036 kg, The charged molar ratio of S-DCDPS and DCBN was 38:62. Further, 2.9679 kg of 4,4′-biphenol and 2.4213 kg of potassium carbonate were weighed and put into a polymerization tank to flow nitrogen. After adding 25.9 kg of NMP and stirring at 150 ° C. for 50 minutes, the reaction temperature was increased to 195 ° C. to 200 ° C. to continue the reaction. Thereafter, the mixture was allowed to cool, and after cooling, the polymerization solution was precipitated into a water bath. The obtained polymer was washed in boiling water for 1 hour and then carefully washed with pure water to remove residual potassium carbonate. Thereafter, the polymer after removing potassium carbonate was dried to obtain a copolymerized SPAE having a sulfonation degree DS = 38%, which was the target product.

  DMSO was added to the obtained SPAE and dissolved while stirring at room temperature to obtain a 1.0 mass% SPAE coating solution.

The PPE hollow fiber support membrane was dip coated in a SPAE coating solution and dried at 120 ° C. in a vertical drying oven. Thereafter, a plurality of composite separation membranes having a first separation layer made of SPAE were wound around a winder. As a result of observation by SEM, the thickness of the first separation layer was 300 nm. At this time, the water permeability was 30 L / (m ² · h · bar), and the NaCl rejection was 11%.

(Manufacture of modules)
A module of the type shown in FIG. 3 was produced as follows. One yarn bundle in which 70,000 hollow fiber membranes were bundled in parallel was prepared, one end of the yarn bundle was cut, and the opening surface was clogged with a hot melt of polyolefin. This end was placed in a polytetrafluoroethylene (PTFE) mold making container having an inner diameter of 80 mm, filled with an epoxy resin and hardened, and then released to obtain an adhesive end (A11).
Further, the periphery of the above-mentioned yarn bundle is wound with a PTFE film having a thickness of 50 μm to protect the outer surface, and the inner diameter is 100 mm and the length is 1,000 mm provided with two supply liquid inlets / outlets (A4, A5). A cylindrical container made of polyvinyl chloride was filled. Thereafter, the PTFE film was pulled out. Subsequently, with the cylindrical container fixed in an upright state, with the adhesive end (A11) on the upper side and the other end on the lower side, an epoxy resin is poured from the lower part of the cylindrical container, and end bonding is performed. An adhesive end (A2) was obtained. The opening end (A1) was cut so that the hollow fiber membrane was opened after the resin was cured. A cap (A9) was vertically attached to this module to produce a hollow fiber membrane module having a first separation layer.

(Hydrophilization / moisture treatment)
The module thus produced was filled with ethanol from the lower inlet (A12) and subjected to a hydrophilic treatment for 2 hours. Thereafter, ethanol was replaced with pure water. Subsequently, a cross flow operation was performed with pure water at a pressure of 2 bar to remove ethanol in the membrane.

Example 1
(Formation of second separation layer)
Pure water was extracted from the water-containing module, and a 0.1 mass% aqueous solution in which CPVA (K434, manufactured by Nippon Synthetic Chemical Co., Ltd.) was dissolved in pure water was filled in the module. After performing the adsorption treatment by standing for 30 minutes, rinsing was performed with pure water for 5 minutes. Subsequently, a 0.1 mass% aqueous solution in which APVA (CKS50 manufactured by Nippon Synthetic Chemical Co., Ltd.) was dissolved in pure water was filled in the module. After performing the adsorption treatment by allowing to stand for 30 minutes, the rinse treatment was carried out with pure water for 5 minutes. Thereafter, a 1% by mass glutaraldehyde (GA) aqueous solution (added sulfuric acid as an acid catalyst and adjusted to pH = 1) was filled and subjected to crosslinking treatment for 20 hours. After the inside of the module was sufficiently washed with pure water, another treatment cycle of CPVA and APVA adsorption treatment and glutaraldehyde crosslinking was performed. Finally, it was sufficiently washed with pure water to obtain a hollow fiber membrane module having a second separation layer.

The final module performance was 865 L / h for pure water permeation at a pressure of 5 bar and 17.8 L / (m ² · h) for pure water flux. Further, the MgSO ₄ blocking rate was 98.3%, the NaCl blocking rate was 64.0%, the sucrose blocking rate was 99.2%, and the glucose blocking rate was 90.1%.

Next, the module was filled with an aqueous solution of sodium hypochlorite (manufactured by Nacalai Tesque) adjusted to a concentration of 300 ppm and pH = 12. Hold at room temperature, replace sodium hypochlorite aqueous solution every 12 hours, measure the chlorine concentration before and after with HANNA's digital residual chlorine meter (UHR) HI771, and multiply the average value of 2 chlorine concentrations by 12 hours The exposure time (ppm · hours) was calculated. Thereafter, the MgSO ₄ rejection rate and pure water flux of the module were measured. This cycle of chlorine exposure test and membrane performance test was repeated.

When the accumulated chlorine exposure reached 48,000 ppm · hours, the MgSO ₄ rejection decreased from the initial value of 98.3% to 83.1%. Here, a 0.1 mass% aqueous solution in which CPVA (Nippon Synthetic Chemical Co., Ltd. K434) was dissolved in pure water was filled in the module. After performing the adsorption treatment by allowing to stand for 30 minutes, rinsing was performed for 5 minutes while substituting with pure water. Thereafter, a 0.1% by mass aqueous solution in which APVA (manufactured by Nippon Synthetic Chemical Co., Ltd. CKS50) was dissolved in pure water was filled in the module, and the module was allowed to stand for 30 minutes for adsorption treatment. After rinsing for 5 minutes while substituting with pure water, 1% by mass glutaraldehyde (GA) aqueous solution (added sulfuric acid as acid catalyst, adjusted to pH = 1) was charged, and crosslinking treatment was performed for 20 hours. It was. As a result, the MgSO ₄ rejection was recovered from 83.1% to 95.2%.

(Example 2)
About the module which performed the membrane performance recovery process in Example 1, 300 ppm sodium hypochlorite aqueous solution immersion was continued and implemented. When the cumulative chlorine exposure including Example 1 reached 90,000 ppm · hours, the MgSO ₄ rejection decreased to 89.9%.

Here, a 0.1 mass% aqueous solution in which CPVA (Nippon Synthetic Chemical Co., Ltd. K434) was dissolved in pure water was filled in the module. After performing the adsorption treatment by allowing to stand for 30 minutes, rinsing was performed for 5 minutes while substituting with pure water. Thereafter, a 0.1% by mass aqueous solution in which APVA (manufactured by Nippon Synthetic Chemical Co., Ltd. CKS50) was dissolved in pure water was filled in the module, and the module was allowed to stand for 30 minutes for adsorption treatment. After rinsing for 5 minutes while substituting with pure water, 1% by mass glutaraldehyde (GA) aqueous solution (added sulfuric acid as acid catalyst, adjusted to pH = 1) was charged, and crosslinking treatment was performed for 20 hours. It was. Thereafter, a cycle of adsorption treatment of CPVA / APVA aqueous solution and crosslinking treatment with GA aqueous solution was further repeated under the same conditions as described above. As a result, the MgSO ₄ rejection was recovered to 98.0%.

FIGS. 1 and 2 show the changes in the MgSO ₄ blocking rate and the pure water flux during the exposure to sodium hypochlorite and the membrane regeneration treatment in Examples 1 and 2 above.

(Example 3)
(Formation of second separation layer)
Pure water was extracted from the module after the hydrophilization / moisture treatment, and a 0.1 mass% aqueous solution in which CPVA (Kuraray CM318) was dissolved in pure water was filled in the module. After performing the adsorption treatment by standing for 30 minutes, rinsing was performed with pure water for 5 minutes. Thereafter, a rinse treatment was performed for 5 minutes with pure water, and a 1% by mass glutaraldehyde (GA) aqueous solution (added with sulfuric acid as an acid catalyst and adjusted to pH = 1) was charged, followed by a crosslinking treatment for 20 hours. After sufficiently washing the inside of the module with pure water, another CPVA adsorption treatment and glutaraldehyde crosslinking treatment cycle were performed. Finally, it was sufficiently washed with pure water to obtain a hollow fiber membrane module having a second separation layer.

The final module performance was 915 L / h of pure water permeation at a pressure of 5 bar and 18.5 L / (m ² · h) of pure water flux. Further, the MgSO ₄ blocking rate was 97.5%, the NaCl blocking rate was 61.0%, the sucrose blocking rate was 98.8%, and the glucose blocking rate was 89.4%.

Next, the concentration 300ppm module, pH = 12 sodium hypochlorite was prepared by filling an aqueous solution of (Nacalai Tesque), Example 1 a similar manner to the module MgSO ₄ rejection and Jun A chlorine exposure test was performed while measuring the water flux.

When the cumulative chlorine exposure reached 50,000 ppm · hours, the MgSO ₄ rejection decreased from 97.5% of the initial value to 84.8%. Here, a 0.1 mass% aqueous solution in which CPVA (Kuraray CM318) was dissolved in pure water was filled in the module. After performing the adsorption treatment by allowing to stand for 30 minutes, rinsing was performed for 5 minutes while substituting with pure water. Thereafter, a 1% by mass glutaraldehyde (GA) aqueous solution (added sulfuric acid as an acid catalyst and adjusted to pH = 1) was filled and subjected to crosslinking treatment for 20 hours. As a result, the MgSO ₄ rejection was recovered from 84.8% to 94.2%.

(Comparative Example 1)
A hollow fiber composite membrane module was produced in the same manner as in Example 1. The final module performance was such that the pure water permeation amount at a pressure of 5 bar was 853 L / h, and the pure water flux was 17.3 L / (m ² · h). Further, the MgSO ₄ blocking rate was 98.5%, the NaCl blocking rate was 64.5%, the sucrose blocking rate was 99.1%, and the glucose blocking rate was 91.2%.

Next, the concentration 300ppm module, pH = 12 sodium hypochlorite was prepared by filling an aqueous solution of (Nacalai Tesque), Example 1 a similar manner to the module MgSO ₄ rejection and Jun A chlorine exposure test was performed while measuring the water flux.

When the cumulative chlorine exposure reached 52,000 ppm · hours, the MgSO ₄ rejection decreased from 98.5% of the initial value to 79.5%. Here, a 0.1 mass% aqueous solution in which CPVA (Nippon Synthetic Chemical Co., Ltd. K434) was dissolved in pure water was filled in the module. After performing the adsorption treatment by allowing to stand for 30 minutes, rinsing was performed for 5 minutes while substituting with pure water. Thereafter, a 0.1% by mass aqueous solution in which APVA (manufactured by Nippon Synthetic Chemical Co., Ltd. CKS50) was dissolved in pure water was filled in the module, and the module was allowed to stand for 30 minutes for adsorption treatment. The rinse treatment was performed for 5 minutes while substituting with pure water. When the film performance was evaluated without performing the crosslinking treatment, the MgSO ₄ blocking rate was 79.5% to 79.8%, and a clear performance recovery effect could not be obtained.

  The composite membrane module whose performance has been greatly reduced due to chemical degradation as in Examples 1 to 3 is repaired in situ by a very simple and inexpensive process of filling the module with a modified polyvinyl alcohol aqueous solution and an aldehyde aqueous solution. It became clear that we could do it.

  Hereinafter, measurement and evaluation methods in the present invention will be described.

(Measurement of sulfonation degree DS of SPAE polymer)
The degree of sulfonation DS of the SPAE polymer was evaluated as follows. 20 mg of a polymer dried at 100 ° C. overnight in a vacuum dryer was dissolved in 1 mL of deuterated DMSO (DMSO-d6) manufactured by Nacalai Tesque, and this was dissolved in AVANCE 500 (frequency: 50.13 MHz, temperature: 30 ° C., manufactured by BRUKER). Proton NMR measurement was performed at FT integration 32 times). In the obtained spectrum chart, the relationship between each proton contained in the hydrophobic segment and the hydrophilic segment and the peak position is identified, and the independent peak among the protons in the hydrophobic segment and the independent peak among the protons in the hydrophilic segment Was obtained from the ratio of the integrated intensity per proton.

(Shape of hollow fiber membrane)
An appropriate amount of a hollow fiber bundle was packed into a 3 mm-thick SUS plate hole with a 3 mm diameter or 6 mm diameter hole, cut with a razor blade to expose the cross section, and then a Nikon microscope (ECLIPSE LV100) and Using a Nikon image processing device (DIGITAL SIGN DS-U2) and a CCD camera (DS-Ri1), the shape of the cross-section is photographed, and a hollow fiber membrane cross-section is obtained using image analysis software (NIS Element D3.00 SP6). The outer diameter, inner diameter and thickness of the hollow fiber membrane were calculated by measuring the outer diameter and inner diameter of the hollow fiber membrane using the measurement function of the analysis software.

(Thicknesses of the first separation layer and the second separation layer)
The hollow fiber membrane in a water-containing state is frozen with liquid nitrogen, cleaved, air-dried, and Pt is sputtered onto the fractured surface. Using a scanning electron microscope S-4800 manufactured by Hitachi, Ltd., at an acceleration voltage of 5 kV Observed.

(Filtration evaluation of hollow fiber membrane module)
About the module produced by the Example and the comparative example, it connected to the module test apparatus which consists of a supply water tank and a pressure pump, and performed the filtration test by the crossflow. The evaluation pressure was unified at 5 bar (0.5 MPa), and the supply liquid temperature was unified at 25 ° C. The feed liquid flow rate was adjusted so that the recovery rate was 5%. Sodium chloride (NaCl), magnesium sulfate (MgSO ₄ ), sucrose (molecular weight 342), and glucose (molecular weight 180) were used as solutes for the separation test. All solute concentrations were adjusted to 1500 mg / L. After performing the filtration operation for about 1 hour, the amount of permeated water from the membrane was measured with the flow meter of the test apparatus, the permeate was sampled, and the solute concentration was measured.
The water permeation amount (FR) per pressure was calculated from the following formula.
FR [L / (m ² · h · bar)] = permeated water amount [L] / membrane area [m ² ] / collection time [min] / operating pressure [bar]

When the feed solution is NaCl or MgSO ₄ , the conductivity of the membrane permeate collected in the filtration test and the feed aqueous solution is measured using an electric conductivity meter (Toa DKK Corporation CM-25R), and the ion blocking rate is measured. Was calculated from the following formula.
Blocking rate [%] = (1−conductivity of filtrate [μS / cm] / conductivity of feed aqueous solution [μS / cm]) × 100

When the feed solution was sucrose or glucose, the membrane permeated water collected by the water permeation measurement and the sugar concentration of the feed aqueous solution were evaluated by the phenol-sulfuric acid method. Specifically, 1.0 mL of the above-mentioned supply liquid or permeate diluted 10-fold with pure water is placed in a test tube, and 1.0 mL of a 5% phenol aqueous solution is added and stirred. On top of that, 5.0 mL of concentrated sulfuric acid (96% concentration) is quickly added and stirred. The colored solution is subjected to absorbance measurement at 490 nm, the concentration is calculated from a calibration curve prepared in advance, and the value obtained by multiplying by 10 is used as the actual concentration value. In the phenol-sulfuric acid method, the range where the linearity between each sugar concentration and absorbance is good is from 0 to 200 mg / L. Therefore, the above-mentioned 1500 mg / L supply solution or filtrate is diluted 10 times and measured. I do. The solute rejection was calculated from the following equation.
Blocking rate [%] = (1−sugar concentration of the filtrate [mg / L] / sugar concentration of the feed aqueous solution [mg / L]) × 100

  According to the present invention, in the composite membrane module having a specific separation membrane configuration, the performance of the module whose membrane performance has deteriorated due to chemical cleaning can be regenerated a large number of times by simple processing. It is possible to extend the life.

A1: Hollow fiber membrane opening surface
A2: Adhesion 1
A3: Hollow fiber membrane bundle
A4: Supply liquid inlet
A5: Supply liquid outlet
A6: Permeate collector
A7: Permeate outlet
A8: Pressure vessel
A9: Cap
A10: Joint
A11: Adhesive part 2
A12: Cleaning fluid inlet

Claims (5)

  A first separation layer composed of an anionic polymer on one surface of the porous support membrane, and a second composed of at least one kind of cationic or anionic polymer on the surface of the first separation layer; A method for regenerating a membrane module incorporating a composite membrane having a separation layer, the step of bringing at least one kind of cationic polymer solution or anionic polymer solution into contact with the separation layer side of the composite membrane, and a crosslinking agent solution A method for regenerating a membrane module, wherein the steps of contacting are sequentially performed.   The method according to claim 1, wherein the cationic polymer solution is a cationic polyvinyl alcohol aqueous solution.   The method according to claim 1, wherein the anionic polymer solution is an aqueous anionic polyvinyl alcohol solution.   The method according to claim 1, wherein the crosslinking agent solution is an aqueous solution of aldehydes.   The method according to any one of claims 1 to 4, wherein the step of contacting the cationic polymer solution or the anionic polymer solution and the step of contacting the crosslinking agent solution are repeated twice or more in order.