JP2010227757A - Composite separation membrane - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a composite separation membrane which is excellent in a separation characteristic, a water permeability performance, chemical strength (chemical resistance), physical strength and an antifouling property, which can separate a low molecular compound and an ion that can be hardly separated by a conventional microfiltration membrane or a conventional ultrafiltration membrane and which is effective in boron removal or the like from seawater and further to provide a water treating apparatus using the composite separation membrane and a method for driving the same. <P>SOLUTION: The composite separation membrane contains a layer of three dimensional network structure which is formed of a thermoplastic resin (A) and has an average pore diameter of a surface between 0.01 μm and 1 μm and a layer made of porous structure which is formed of a thermoplastic resin (B) and contains an adsorbent. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to microfiltration membranes and ultrafiltration membranes used in water treatment fields such as drinking water production, water purification treatment, wastewater treatment and seawater desalination pretreatment, and a water treatment method using them.

  In recent years, separation membranes have been used in various fields such as water treatment fields such as water purification treatment and wastewater treatment, medical applications such as blood purification, food industry fields, battery separators, charged membranes, fuel cell electrolyte membranes and the like.

  In particular, in the field of drinking water production, that is, water purification applications such as water purification treatment, wastewater treatment, and seawater desalination, separation membranes are used to replace conventional sand filtration, coagulation sedimentation, and evaporation methods, and to improve the quality of treated water. Is being used. Since the amount of treated water is large in these fields, if the water permeability of the separation membrane is excellent, it is possible to reduce the membrane area, and the equipment can be reduced because the equipment is compact, and the membrane replacement cost and installation area are reduced. Will also be advantageous.

  Separation membranes for water treatment are microfiltration membranes (MF membranes), ultrafiltration membranes (UF membranes), nanofiltration membranes (NF membranes), reverse osmosis membranes (depending on the size of the substance to be separated contained in the water to be treated. RO membrane) is used.

  Especially in seawater desalination applications, extremely small substances such as boron contained in trace amounts in seawater are difficult to remove completely with these membranes. Even when reverse osmosis membranes are used, they are defined in the WHO Water Quality Guidelines. It is not easy to make the boron concentration below the provisional value (0.5 mg / L) or less. If the structure of the membrane is made dense in order to increase the removal rate, there is a problem that water permeability performance is lowered, a large pressure is required for filtration, and processing costs are increased.

  Therefore, a water treatment method is disclosed in which seawater is supplied to the first reverse osmosis membrane module, the permeated water is adjusted to pH 5.7 or higher, and then supplied to the second reverse osmosis membrane module (Patent Document 1). ). However, use of the reverse osmosis membrane module in multiple stages not only increases the equipment cost and the power cost, but also increases the chemical cost for adjusting the pH, which is not economical.

  On the other hand, as a method for removing boron, besides the reverse osmosis membrane method, adsorption removal with a strongly basic anion exchange resin, adsorption removal with a resin obtained by binding N-methylglucamine to a styrene-divinylbenzene copolymer, cerium A method of adsorbing and removing with an inorganic adsorbent such as a compound (Patent Document 2) is known, and a water treatment method is disclosed in which permeated water of a reverse osmosis membrane module is passed through an ion exchange resin layer to remove boron. (Patent Document 3).

  However, there is a problem in terms of economy because the equipment cost of the adsorption tower, the initial investment of the resin, and the regeneration cost of the resin are high.

  In the adsorption removal of boron by activated carbon, it is reported that about 90% of boron is removed from the solution by stirring the activated carbon-containing solution for about 40 hours (for example, Non-Patent Document 1).

  However, in an actual water treatment plant, such long-time adsorption treatment is inefficient and has a problem in terms of economy.

  In addition, MF membranes and UF membranes are used for pretreatment for supplying seawater to the reverse osmosis membrane module. By incorporating an adsorbent into these membranes, the boron concentration can be reduced at the pretreatment stage. A method of reducing it is conceivable. For example, a hollow fiber-shaped filter medium in which cerium hydrated oxide is blended with a polymer material has been proposed (Patent Document 4).

  However, the main use of the hollow fiber membrane described in Patent Document 4 is to remove phosphorus from the blood, and although the description “filtration of drinking water” is slightly seen, the hollow fiber membrane used for water treatment is used. There is no detailed description of the thread membrane in the text and no examples. In general, hollow fiber membrane modules used for artificial dialysis are disposable, and durability and stain resistance need only be able to withstand treatment for several hours. However, hollow fiber membrane modules for water treatment have been used for about 5 to 10 years. In order to achieve the separation characteristics, chemical resistance, permeation performance, and especially physical strength and fouling resistance required for water treatment membranes, advanced technology and various devices are required. However, there is no suggestion or description about them.

  Further, most of the filter media disclosed in Patent Document 4 are those of a single-layer hollow fiber membrane supporting cerium hydroxide, and a technique for coating the surface of the hollow fiber membrane is also described. Although it is a hollow fiber membrane having a multilayer structure by covering the filtrate side so that cerium hydroxide is not taken into the human body. For this reason, it has been unrealistic to apply to water treatment applications that require high separation characteristics, chemical resistance, permeation performance, physical strength, fouling resistance, and the like.

  As described above, there has been no microfiltration membrane or ultrafiltration membrane that achieves the reduction of low-molecular compounds and ions typified by boron and the like and the removal of turbidity and microorganisms at the same time.

Japanese Patent Laid-Open No. 9-10766 JP 2007-160271 A Japanese Patent Laid-Open No. 10-15356 JP 2004-305915 A

“Environmental Science and Technology”, Vol. 13, no. 2, 1979, p. 189-196

  In view of the above-mentioned problems of the prior art, the present invention is excellent in separation characteristics, water permeability, chemical strength (chemical resistance), physical strength, and fouling resistance, and is also equipped with conventional microfiltration membranes and ultrafiltration membranes. It is an object of the present invention to provide a composite membrane that can separate or reduce low-molecular compounds and ions that have been difficult to separate, and is effective for removing boron from seawater, a water treatment apparatus using the composite membrane, and an operation method thereof.

  As a result of intensive studies, the present inventors have conceived that the adsorbent is contained in a layer having a porous structure mainly giving physical strength, not a layer having a three-dimensional network structure having a separation function such as salt. However, a composite separation membrane having a layer having a three-dimensional network structure with a controlled pore size and a layer having a porous structure containing an adsorbent is extremely effective for solving the above-mentioned problems. The headline, the present invention has been reached.

That is, this invention is comprised by the following characteristics.
(1) A layer having a three-dimensional network structure having an average surface pore size of 0.01 μm or more and 1 μm or less formed from the thermoplastic resin (A) and the thermoplastic resin (B), and containing an adsorbent. A composite separation membrane comprising a layer having a porous structure.
(2) The composite separation membrane according to (1), wherein the adsorbent contains one or more inorganic compounds selected from cerium hydroxide and cerium hydrated oxide.
(3) The thermoplastic resin (A) and the thermoplastic resin (B) contain polyvinylidene fluoride, and a layer composed of a porous structure containing an adsorbent forms a spherical structure, and the adsorbent is present in the pores. The composite separation membrane according to (1) or (2), wherein

  According to the present invention, it has excellent separation characteristics, water permeability, chemical strength (chemical resistance), physical strength, fouling resistance, and can separate low molecular weight compounds and ions. Boron removal from seawater, etc. It is possible to provide a composite separation membrane that is effective for water, a water treatment apparatus using the same, and an operation method thereof.

The composite separation membrane of the present invention is characterized by having both a layer having a three-dimensional network structure having a surface average pore size of 0.01 μm or more and 1 μm or less and a layer having a porous structure. Here, the three-dimensional network structure refers to a structure in which the solid content spreads in a three-dimensional network. The three-dimensional network structure has pores partitioned into solid contents forming a network. In the present invention, the layer having a three-dimensional network structure mainly assumes the separation function. In order to achieve both high blocking performance, water permeability, and anti-fouling performance, the average pore diameter of the surface of the three-dimensional network structure needs to be 0.01 μm or more and 1 μm or less, preferably 0.01 μm or more and 0.5 μm or less. Therefore, the blocking performance, water permeation performance, and anti-fouling performance can be achieved at a higher level, which is preferable. The average pore diameter on the surface of the three-dimensional network structure is an average pore diameter of pores existing on the surface of the layer of the three-dimensional network structure as viewed from the supply side. The average pore diameter of the pores is determined by taking a photograph using a scanning electron microscope (SEM) or the like at a magnification at which the pores can be clearly confirmed on the surface of the porous membrane. It can be determined by measuring the diameter of the holes and averaging the numbers. An average value of the diameters of the pores can be obtained using an image processing apparatus or the like, and the average of the equivalent circular diameters can be preferably used as the average pore diameter. In the case of an elliptical shape, the average equivalent circular diameter can be obtained by (a × b) ^0.5 , where a is the minor axis and b is the major axis.

  The three-dimensional network structure may be configured to have macrovoids having an average pore diameter exceeding 50 μm in order to obtain a film having high permeability.

  The porous structure of the present invention refers to a structure having innumerable minute pores inside. Examples of the porous structure include a three-dimensional network structure, a spherical structure, a cell structure, a honeycomb structure, a finger structure, etc., and the shape is not particularly limited, but the spherical structure is particularly excellent in balance of strength and transmission performance, In addition, the adsorbent is preferably exposed without being buried in the resin while being held in the pores.

  The spherical structure refers to a structure in which a large number of spherical or substantially spherical solids are connected directly or via streak-like solids. The spherical structure is presumed to consist exclusively of spherulites. The spherulite is a crystal in which a thermoplastic resin is precipitated and solidified into a spherical shape when a thermoplastic resin solution is phase-separated to form a porous structure. A membrane having a spherical structure can obtain a membrane having high strength while maintaining permeation performance. By setting the average diameter of the spherical structure to 0.5 μm or more and 5 μm or less, more preferably 1.0 μm or more and 3 μm or less, the strength and transmission performance can be balanced at a higher level.

  In addition, the composite separation membrane of the present invention is characterized by containing an adsorbent in a layer having a porous structure. The adsorbent of the present invention is a phenomenon in which the density of a substance in one phase or the concentration of a solute dissolved in the phase is higher than that in the bulk phase due to the interaction at the interface where two phases are in contact ( This refers to a substance used in a process for separating and removing substances using an adsorption phenomenon). Examples of the adsorbent usable in the present invention include carbon-based adsorbents such as charcoal, bamboo charcoal, activated carbon, carbon fiber, molecular sieve carbon, carbon nanotube, and mesoporous carbon, silica gel, macroporous silica, activated alumina, zeolite, smectite, hydroxy Inorganic adsorbents such as apatite, metal hydroxide, metal hydrated oxide, ion exchange resins, chelate resins, organic metal complexes, chitosan, cellulose and other organic adsorbents, inorganic mesoporous materials, organic-inorganic hybrid mesoporous materials, carbon A gel etc. are mentioned, These can use 1 type or more. Among these adsorbents, zeolite, metal hydroxide, and metal hydrated oxide are particularly preferable from the viewpoints of separation characteristics, water permeability, chemical resistance, physical strength, and dispersibility in the composite membrane. In particular, zeolite, metal hydroxide, and metal hydroxide are preferably used from the viewpoint of low molecular organic compounds and ion removal performance.

The zeolite of the present invention is a compound having a composition AB _n (n≈2) that forms an open three-dimensional network defined by the International Zeolite Society, and A has 4 bonds and B has 2 bonds. It is a substance having a skeleton density of 20.5 or less, and is generally a crystalline aluminosilicate.

  The type of the zeolite in the present invention is not particularly limited as long as the above definition is satisfied. For example, a faujasite type zeolite such as X type and Y type, a pentasil type zeolite such as ZSM-5, a mordenite type zeolite, L-type zeolite, beta-type zeolite, A-type zeolite and the like are preferably used. In particular, A-type zeolite having high affinity with water is preferable.

  In the present invention, it is preferable to use a rare earth element hydroxide or a rare earth element hydroxide as the metal hydroxide or metal hydroxide. Here, the rare earth elements are scandium Sc of atomic number 21 and yttrium Y of 39, lanthanoid elements of 57 to 71, that is, lanthanum La, cerium Ce, praseodymium Pr, neodymium Nd, and promethium Pm. Samarium Sm, Europium Eu, Cadolinium Gd, Terbium Tb, Dysprosium Dy, Holmium Ho, Erbium Er, Thulium Tm, Ytterbium Yb, Lutetium Lu. Among these, a preferable element from the viewpoint of ion removal performance is cerium, and tetravalent cerium is preferable. Mixtures of these rare earth element hydroxides and / or hydrated oxides are also useful.

  The composite separation membrane of the present invention needs to have a structure in which a layer of a three-dimensional network structure and a layer of a porous structure are laminated in order to achieve both strength, permeation performance and blocking performance at a high level. It is. Further, the composite separation membrane of the present invention has a separation characteristic required for a water treatment membrane by disposing a layer composed of a three-dimensional network structure on the supply side of the substance to be separated and a layer composed of a porous structure on the permeation side. , Low molecular weight organic compounds and ions that were difficult to separate and remove with conventional water treatment membranes without impairing properties such as permeation performance, chemical strength (chemical resistance), physical strength, and fouling resistance It was found that the removal performance can be greatly improved.

Although the size of the adsorbent used in the present invention is not particularly limited, the average particle size is 0.01 to 10 μm, preferably 0.1 to 5 μm, more preferably 0.5 to 3 μm. The pore size in the porous structure and the adsorbent size are preferably as close as possible. The size of the adsorbent is obtained by taking a photograph of the primary particles of the adsorbent using SEM or the like, measuring any diameter of 10 or more, preferably 20 or more, and averaging the numbers. When the shape is other than a circle, if the diameter of the circle inscribed in the shape is a and the diameter of the circumscribed circle is b, (a × b) ^0.5 is obtained as the equivalent circle diameter.

  A commercially available thing can be obtained and used for the adsorption agent used by this invention. For example, it can be purchased from a reagent company, or directly from a manufacturing company described in “15308 Chemical Products” (Chemical Industry Daily).

  Regarding the weight ratio of the thermoplastic resin (B) / adsorbent in the layer having the porous structure of the present invention, it is 95/5 to 50 in terms of 99/1 to 1/99 parts by weight, physical strength, and separation characteristics. / 50 is preferable, and more preferably 90/10 to 70/30.

The composite separation membrane of the present invention has a water permeability at 50 kPa and 25 ° C. of 0.1 m ³ / m ² / hr or more and 5 m ³ / m ² / hr or less, a rejection rate of 0.309 μm diameter particles is 90% or more, and a breaking strength Is preferably 2 MPa or more and the elongation at break is 5% or more. The water permeability is more preferably 0.15 m ³ / m ² / hr or more and 3 m ³ / m ² / hr or less. The rejection of 0.309 μm diameter particles is more preferably 95% or more. The breaking strength is more preferably 3 MPa or more. The breaking elongation is more preferably 10% or more. By satisfying the above conditions, a composite membrane having sufficient strength, permeation performance and blocking performance for applications such as water treatment, battery separators, charged membranes, fuel cell electrolyte membranes, and blood purification membranes can be obtained. it can.

  The composite separation membrane of the present invention can be preferably used in either a hollow fiber membrane shape or a flat membrane shape.

The measurement method of the water permeation performance and the blocking performance can be measured by producing a miniature module having a length of 200 mm and comprising four hollow fiber membranes. Under the conditions of a temperature of 25 ° C. and a filtration differential pressure of 16 kPa, the external pressure total filtration of reverse osmosis membrane filtrate was performed for 30 minutes, and the permeation amount (m ³ ) was determined. Permeability (m ³ ) is converted to a value per unit time (h) and effective membrane area (m ² ), and is further multiplied by (50/16) to convert it to a value at a pressure of 50 kPa. Can be requested. Further, external pressure total filtration of filtered water in which polystyrene latex particles having an average particle size of 0.309 μm were dispersed was performed for 30 minutes under the conditions of a temperature of 25 ° C. and a filtration differential pressure of 16 kPa. The concentration of latex particles in raw water and permeated water can be determined by measuring the ultraviolet absorption coefficient at a wavelength of 240 nm, and the blocking performance can be determined from the concentration ratio. In the case of a flat membrane, the membrane can be obtained by cutting the membrane into a circle having a diameter of 50 mm, setting it in a cylindrical filtration holder, and performing the other operations in the same manner as the hollow fiber membrane. The water permeation performance may be obtained by converting a value obtained by pressurization or suction with a pump or the like. The water temperature may also be converted by the viscosity of the evaluation liquid. When the water permeability is less than 0.1 m ³ / m ² / hr, the water permeability is too low, which is not preferable as a composite separation membrane. On the other hand, if the water permeability exceeds 5 m ³ / m ² / hr, the pore size of the composite separation membrane is too large, and the impurity blocking performance is lowered, which is not preferable. Even when the rejection rate of 0.309 μm diameter particles is less than 90%, the pore size of the composite separation membrane is too large, and the impurity rejection performance is lowered, which is not preferable.

  The method for measuring the breaking strength and breaking elongation is not particularly limited. For example, using a tensile tester, a sample having a measurement length of 50 mm is subjected to a tensile test at a pulling speed of 50 mm / min, and the sample is changed five times. This can be calculated by calculating the average value of the breaking strength and the average value of the breaking elongation. When the breaking strength is less than 2 MPa or the breaking elongation is less than 5%, the handling property when handling the composite separation membrane is deteriorated, and the membrane is easily broken or crushed during filtration.

  The thermoplastic resin (A) and the thermoplastic resin (B) used in the present invention are resins made of a chain polymer material and exhibiting a property of being deformed / flowed by an external force when heated. Examples of thermoplastic resins include polyethylene resins, polypropylene resins, acrylic resins, polyacrylonitrile, acrylonitrile-butadiene-styrene (ABS) resins, polystyrene, acrylonitrile-styrene (AS) resins, polyvinyl chloride resins, polyethylene terephthalate, Examples thereof include polyamide, polyacetal, polycarbonate, modified polyphenylene ether, polyphenylene sulfide, polyvinylidene fluoride resin, polyamide imide, polyether imide, polysulfone, polyether sulfone, cellulose derivative, and mixtures and copolymers thereof. Other resins miscible with these may be mixed.

  The thermoplastic resin (A) used in the present invention is selected from polyethylene resins, polypropylene resins, polyvinylidene fluoride resins, polyacrylonitrile, polysulfone, polyethersulfone, and cellulose derivatives. It can be preferably used from the viewpoint of strength, and among these, polyvinylidene fluoride resin is most preferable.

  As the thermoplastic resin (B) used in the present invention, those selected from polyethylene resins, polypropylene resins, polyvinylidene fluoride resins, polyacrylonitrile, polysulfone, polyethersulfone, and cellulose derivatives are chemically resistant, physically It can be preferably used in terms of strength and affinity with the adsorbent. Among these, polyvinylidene fluoride resins are preferably used because they are most excellent in the balance of the above characteristics.

  The polyvinylidene fluoride resin in the present invention is a resin containing a vinylidene fluoride homopolymer and / or a vinylidene fluoride copolymer. A plurality of types of vinylidene fluoride copolymers may be contained. Examples of the vinylidene fluoride copolymer include a copolymer of vinylidene fluoride with at least one selected from vinyl fluoride, tetrafluoroethylene, hexafluoropropylene, and ethylene trifluoride chloride. The weight average molecular weight of the polyvinylidene fluoride resin may be appropriately selected depending on the required strength and water permeability of the porous membrane, and is preferably from 50,000 to 1,000,000. In consideration of the workability to the porous film, 100,000 to 700,000 is preferable, and 150,000 to 600,000 is more preferable.

  Further, the thermoplastic resin (A) and the thermoplastic resin (B) may contain 50 wt% or less of other miscible resins. For example, in the case of a polyvinylidene fluoride resin, it is also preferable to contain an acrylic resin in a range of 50% by weight or less. Here, the acrylic resin refers to a polymer compound mainly including a polymer such as acrylic acid, methacrylic acid and derivatives thereof such as acrylamide and acrylonitrile. In particular, acrylic ester resins and methacrylic ester resins are preferably used because of their high miscibility with polyvinylidene fluoride resins. Thus, strength, water permeability, blocking performance, etc. can be adjusted by comprising a polymer blend in which a plurality of resins are mixed.

  Moreover, although a thermoplastic resin (A) and a thermoplastic resin (B) may be comprised by the same resin, you may comprise by a different resin. It is preferable to use the same resin because both have high affinity. On the other hand, when both are comprised by different resin, intensity | strength, water permeability performance, blocking performance, etc. can be adjusted in a wider range.

  The composite separation membrane of the present invention having both a layer composed of a three-dimensional network structure and a layer composed of a porous structure containing an adsorbent can be produced by various methods. For example, a method of later forming a layer having a three-dimensional network structure on at least one side of a layer having a porous structure containing an adsorbent, two or more types of resin solutions are simultaneously discharged from a die, and a tertiary Examples thereof include a method of simultaneously forming both a layer having an original network structure and a layer having a porous structure containing an adsorbent.

  First, as a method for producing a composite separation membrane having both a three-dimensional network structure of the present invention and a porous structure containing an adsorbent, a three-dimensional network is formed on at least one side of the porous membrane containing the adsorbent. A method of forming a layer having a shape structure later will be described.

  In this production method, first, a layer having a porous structure containing an adsorbent is produced. Although the manufacturing method of the layer which consists of a porous structure containing an adsorbent is not specifically limited, It can manufacture preferably with the following method. For example, a thermoplastic resin is dissolved in a poor solvent or a good solvent of the resin at a relatively high concentration of about 10 wt% to 60 wt%, and the adsorbent is uniformly added by adding an adsorbent to the solution. A layer having a porous structure is formed by dispersing and solidifying the dispersion by cooling. Here, the poor solvent means that the resin cannot be dissolved by 5% by weight or more at a low temperature of 60 ° C. or less, but is 60 ° C. or more and the melting point of the resin or less (for example, when the resin is composed of vinylidene fluoride homopolymer alone). Is a solvent that can be dissolved by 5% by weight or more in a high temperature region of about 178 ° C. A solvent capable of dissolving 5% by weight or more of a resin even at a low temperature of 60 ° C. or lower with respect to a poor solvent is defined as a good solvent, and a solvent that does not dissolve or swell the resin up to the melting point of the resin or the boiling point of the liquid is defined as a non-solvent. To do.

  Here, in the case of polyvinylidene fluoride resin, the poor solvent includes medium chain length such as cyclohexanone, isophorone, γ-butyrolactone, methyl isoamyl ketone, dimethyl phthalate, propylene glycol methyl ether, propylene carbonate, diacetone alcohol, glycerol triacetate, etc. And alkyl ketones, esters, glycol esters, organic carbonates, and the like, and mixed solvents thereof. Even if it is a mixed solvent of a non-solvent and a poor solvent, a solvent that satisfies the definition of the poor solvent is defined as a poor solvent. Examples of good solvents include N-methyl-2-pyrrolidone, dimethyl sulfoxide, dimethylacetamide, dimethylformamide, methyl ethyl ketone, acetone, tetrahydrofuran, tetramethylurea, lower alkyl ketones such as trimethyl phosphate, esters, amides, and the like, and mixed solvents thereof. Is mentioned. Further non-solvents include water, hexane, pentane, benzene, toluene, methanol, ethanol, carbon tetrachloride, o-dichlorobenzene, trichloroethylene, ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, butylene glycol, pentanediol. , Hexanediol, aliphatic hydrocarbons such as low molecular weight polyethylene glycol, aromatic hydrocarbons, aliphatic polyhydric alcohols, aromatic polyhydric alcohols, chlorinated hydrocarbons, other chlorinated organic liquids and mixed solvents thereof, etc. Is mentioned.

  In the above production method, first, a thermoplastic resin is dissolved at a relatively high concentration of 10% by weight or more and 60% by weight or less in a poor solvent or a good solvent of the resin at a relatively high temperature of about 80 to 170 ° C. It is preferable to adjust the dispersion by adding the adsorbent to the mixture and uniformly dispersing the adsorbent. When the resin concentration is high, a layer having a porous structure having high strength and elongation characteristics can be obtained. However, when the resin concentration is too high, the porosity of the manufactured layer having a porous structure is reduced, and the water permeability is lowered. Moreover, if the viscosity of the adjusted resin solution is not within an appropriate range, it cannot be formed into a layer having a porous structure. The resin concentration is more preferably in the range of 15% by weight to 50% by weight.

In solidifying the dispersion, by discharging the dispersion from the die into the cooling bath,
It is preferable to solidify by cooling. At this time, the cooling liquid used for the cooling bath is a liquid containing a poor or good solvent having a temperature of 0 to 50 ° C., preferably 5 to 40 ° C., and a concentration of 60 to 100%, preferably 50 to 90%. It is preferable to solidify using. The cooling liquid may contain a non-solvent in addition to the poor solvent and the good solvent.

  By dissolving a thermoplastic resin at a relatively high concentration in a poor solvent or a good solvent of the resin at a relatively high temperature, adding an adsorbent to the solution to uniformly disperse the adsorbent, rapidly cooling and solidifying, The structure of the obtained film can be a fine spherical structure or a dense network structure having no macrovoids. In particular, a film having a spherical structure can obtain high strength and high water permeability. Whether the film structure is a spherical structure or a network structure is controlled by the combination of the concentration and temperature of the resin solution, the composition of the solvent dissolving the resin, and the temperature and composition of the cooling liquid constituting the cooling bath. be able to.

  When the shape of the separation membrane is a hollow fiber membrane, after preparing a dispersion, the dispersion is discharged from a tube outside a double tube die for spinning a hollow fiber membrane, and a hollow portion forming liquid is discharged. It solidifies in a cooling bath while discharging from the tube inside the double-tube type die to form a hollow fiber membrane. At this time, normally, a gas or a liquid can be used as the hollow portion forming fluid, but in the present invention, a liquid containing a poor solvent or a good solvent having a concentration of 60 to 100%, similar to the cooling liquid, is used. Can be preferably employed. Here, the hollow portion forming liquid may be cooled and supplied, but if the hollow fiber membrane is solidified only by the cooling power of the cooling bath, the hollow portion forming liquid is supplied without cooling. You may do it.

  In the case where the shape of the separation membrane is a flat membrane, after preparing a dispersion, the dispersion is discharged from a slit die and solidified in a cooling bath to obtain a flat membrane.

  Furthermore, it is also a preferred embodiment that the separation membrane is accompanied by a porous substrate that supports the separation membrane and gives strength to the separation membrane, since the breaking strength of the separation membrane is increased. The material of the porous base material is not particularly limited, such as an organic material or an inorganic material, but an organic fiber is preferable from the viewpoint of easy weight reduction. More preferably, it is a woven fabric or a nonwoven fabric made of organic fibers such as cellulose fibers, cellulose triacetate fibers, polyester fibers, polypropylene fibers, and polyethylene fibers.

  With the above production method, it is possible to obtain a separation membrane with high strength and elongation characteristics that exhibits water permeability. However, when the water permeability is not sufficient, the separation membrane is further 1.1 times or more and 5.0 times or less. Drawing at a draw ratio is also a preferred embodiment because the water permeability of the separation membrane is improved.

  Next, a layer having a three-dimensional network structure is formed on at least one side of the layer having a porous structure containing the obtained adsorbent. The method is not particularly limited, but the following method can be preferably used. That is, it is a method of forming a layer having a three-dimensional network structure by applying a resin solution to at least one side of a porous film containing an adsorbent and then immersing it in a coagulation liquid.

  Examples of the resin used here are polyethylene resin, polypropylene resin, acrylic resin, polyacrylonitrile resin, acrylonitrile-butadiene-styrene (ABS) resin, polystyrene resin, acrylonitrile-styrene (AS) resin, polyvinyl chloride resin. Polyethylene terephthalate resin, polyamide resin, polyacetal resin, polycarbonate resin, modified polyphenylene ether resin, polyphenylene sulfide resin, polyvinylidene fluoride resin, polyamideimide resin, polyetherimide resin, polysulfone resin, polyethersulfone resin, cellulose resin and These mixtures and copolymers may be mentioned. Other resins miscible with these, polyhydric alcohols and surfactants may be contained in an amount of 50% by weight or less.

  Among these, those selected from polyethylene resins, polypropylene resins, polyvinylidene fluoride resins, polyacrylonitrile resins, polysulfone resins, polyethersulfone resins, and cellulose resins are preferred because of their high chemical resistance, and in particular, polyfluoride. A vinylidene chloride resin is preferably used.

  Moreover, as a solvent which melt | dissolves resin, the good solvent of resin is preferable. As the good solvent, those described above can be used. The resin concentration of the resin solution is usually preferably 5 to 30% by weight, more preferably 10 to 25% by weight. If it is less than 5% by weight, the physical durability of the layer having a three-dimensional network structure is lowered, and if it exceeds 30% by weight, a high pressure is required for permeating the fluid.

  The method of applying the resin solution to at least one side of the layer composed of a porous structure containing an adsorbent is not particularly limited, but a method of immersing a layer composed of a porous structure in the solution, or a porous structure A method of applying the solution to at least one side of the layer made of is preferably used. In the case where the shape of the layer composed of the porous structure is a hollow fiber membrane, as a method of applying the solution to the outer surface side of the hollow fiber membrane, the hollow fiber membrane can be immersed in the solution, A method of dropping the solution or the like is preferably used, and a method of applying the solution to the inner surface side of the hollow fiber membrane is preferably a method of injecting the solution into the hollow fiber membrane. Further, as a method for controlling the coating amount of the solution, in addition to a method for controlling the coating amount of the solution itself, a layer composed of a porous structure is immersed in the solution, or the layer composed of a porous structure is A method of scraping off a part of the solution after applying the solution or blowing it off with an air knife is also preferably used.

  In addition, the coagulating liquid here preferably contains a non-solvent of resin. As the non-solvent, those described above can be used. By bringing the applied resin solution into contact with a non-solvent, non-solvent-induced phase separation occurs, and a layer having a three-dimensional network structure is formed.

  The method for controlling the average pore diameter on the surface of the layer of the three-dimensional network structure in the above range varies depending on the type of the resin, but can be performed, for example, by the following method. By adding an additive for controlling the pore size to the resin solution and forming the layer of the three-dimensional network structure, or after forming the layer of the three-dimensional network structure, The average pore diameter can be controlled. Examples of the additive include organic compounds and inorganic compounds. As the organic compound, those that are soluble in both the solvent of the resin and the non-solvent that causes non-solvent-induced phase separation are preferably used. Examples thereof include water-soluble polymers such as polyvinyl pyrrolidone, polyethylene glycol, polyvinyl alcohol, polyethylene imine, polyacrylic acid, and dextran, surfactants, glycerin, and saccharides. As the inorganic compound, a water-soluble compound is preferably used. For example, calcium chloride, lithium chloride, barium sulfate and the like can be mentioned. Moreover, it is also possible to control the average pore diameter on the surface by controlling the phase separation speed according to the type, concentration and temperature of the non-solvent in the coagulating liquid without using an additive. In general, when the phase separation speed is high, the average pore diameter on the surface is small, and when the phase separation speed is low, the average pore diameter is large. Also, adding a non-solvent to the resin solution is effective for controlling the phase separation rate.

  Furthermore, as another method for producing a composite separation membrane having both a three-dimensional network layer of the present invention and a porous layer containing an adsorbent, two or more types of resin solutions or dispersions are used below. A method of discharging simultaneously from the die and simultaneously forming both a layer having a three-dimensional network structure and a layer having a porous structure containing an adsorbent will be described. In this manufacturing method, for example, a three-dimensional network structure-forming resin solution and a porous structure-forming dispersion liquid containing an adsorbent can be simultaneously discharged from a die and then solidified. According to this method, a layer having a three-dimensional network structure and a layer having a porous structure containing an adsorbent can be formed at the same time, and the manufacturing process can be simplified, which is preferable. Here, the resin solution for forming a three-dimensional network structure is not particularly limited as long as it is a resin solution capable of forming a layer of a three-dimensional network structure by solidifying, but for example, a solution in which a resin is dissolved in a solvent. In addition, non-solvent-induced phase separation is caused by contact with the coagulation bath, and a three-dimensional network structure is formed. Further, the dispersion for forming a porous structure containing an adsorbent is not particularly limited as long as it is a dispersion capable of forming a layer composed of a porous structure containing an adsorbent by solidification. A thermoplastic resin such as vinylidene chloride resin at a relatively high concentration of about 10% by weight to 60% by weight or less and dissolved in a poor solvent or a good solvent of the resin at a relatively high temperature (about 80 to 170 ° C.), An adsorbent is added to the solution to uniformly disperse the adsorbent. Here, as the thermoplastic resin, the adsorbent, the coagulation bath, the poor solvent, and the good solvent, those described above can be preferably used.

  The die for discharging the three-dimensional network structure-forming resin solution and the porous structure-forming dispersion containing the adsorbent simultaneously is not particularly limited, but when the shape of the separation membrane is a flat membrane A double slit shape in which two slits are arranged is preferably used. Further, when the shape of the separation membrane is a hollow fiber membrane, a triple tube type die is preferably used. A resin solution for forming a three-dimensional network structure and a dispersion for forming a porous structure containing an adsorbent are discharged from an outer tube and an intermediate tube of the triple tube cap, and a hollow portion forming liquid is discharged from the inner tube. While discharging, it can be solidified in a cooling bath to form a hollow fiber membrane. When the hollow fiber membrane is manufactured by such a manufacturing method, the amount of the hollow portion forming liquid can be made smaller than the amount of the cooling liquid when the flat membrane is manufactured, which is particularly preferable. By discharging the resin solution for forming the three-dimensional network structure from the outer tube and the dispersion liquid for forming the porous structure containing the adsorbent from the intermediate tube, the layer of the three-dimensional network structure is exposed to the outer side. A hollow fiber membrane having a layer composed of a porous structure containing an inside can be obtained. Conversely, a resin solution for forming a three-dimensional network structure is dispersed from an intermediate tube to form a porous structure containing an adsorbent. By discharging the liquid from the outer tube, a hollow fiber membrane having a layer having a three-dimensional network structure on the inside and a layer having a porous structure containing an adsorbent on the outside can be obtained.

  The composite separation membrane thus obtained can be used for water purification, clean water treatment, wastewater treatment, industrial water production, etc. in the water treatment field. River water, lake water, groundwater, seawater, sewage, wastewater, etc. are treated water. And In particular, low molecular weight compounds and ions that were difficult to separate with conventional separation membranes for water treatment can be efficiently removed, so that they can be used extremely favorably as separation membranes for pretreatment in seawater desalination. I can do it.

  By using the composite separation membrane of the present invention as a separation membrane for pretreatment in seawater desalination, it is possible to remove turbidity contained in seawater and suppress fouling of the reverse osmosis membrane. In addition, the adsorbent compounded in the composite separation membrane adsorbs boron compounds, so it is possible to reduce the boron concentration in seawater supplied to the reverse osmosis membrane, and the boron concentration after seawater desalination treatment is reduced. It can be reduced.

  The above-described separation membrane is housed in a casing having a raw solution inlet and a permeate outlet and is used as a separation membrane module. When the separation membrane is a hollow fiber membrane, the separation membrane module can collect a plurality of hollow fiber membranes and store them in a cylindrical container, and fix both ends or one end with polyurethane, epoxy resin, etc., and collect the permeate. Or by fixing both ends of the hollow fiber membrane in a flat plate shape so that the permeate can be collected. When the separation membrane is a flat membrane, the flat membrane is wound around in an envelope shape around the liquid collection tube and wound into a spiral shape and stored in a cylindrical container so that the permeate can be produced. A flat membrane is arranged on both sides, and the periphery is fixed in a watertight manner so that the permeate can be collected.

  The separation membrane module is used as a water treatment device for treating water or the like by providing a pressurizing means at least on the stock solution side or a suction means on the permeate side. A pump may be used as the pressurizing means, or a pressure due to a water level difference may be used. Moreover, what is necessary is just to utilize a pump and a siphon as a suction means.

  The above-described separation membrane module can be cleaned by a known method such as air cleaning, back-flow cleaning, and chemical-enhanced cleaning. In the present invention, in particular, by performing chemical-enhanced cleaning with an alkaline aqueous solution, Since removal of the fouling substance deposited in the pores and regeneration of the adsorbent can be performed simultaneously, it is economically preferable.

  The chemical strengthening cleaning in the present invention is a method of cleaning with backwashing water added with chemicals or immersing with raw water or filtered water added with chemicals. The chemical strengthening cleaning interval is performed once every several hours to several days.

  The chemical used in chemical-strengthened cleaning is preferably an aqueous alkali solution such as sodium hydroxide because it simultaneously removes fouling substances and regenerates the adsorbent. However, depending on the quality of the feed water, oxidation of hypochlorous acid, etc. It can also be combined with cleaning with an agent, an inorganic acid such as sulfuric acid, hydrochloric acid or nitric acid, or an organic acid such as citric acid or oxalic acid. Further, in addition to chemical solution enhanced cleaning, air cleaning, back-flow cleaning, and chemical cleaning can be used in combination.

  About the density | concentration of a chemical | medical agent, although it can adjust suitably with a cleaning effect, in the case of sodium hydroxide aqueous solution, the range of 0.1-5 g / L is preferable.

  As a specific method for cleaning the chemical solution, for example, a sodium hydroxide aqueous solution is passed in the direction opposite to the filtration, and the flow is stopped for about 20 minutes in this state to bring the membrane into contact with the chemical solution, followed by rinsing. It is possible to perform the filtration again. In addition, as described in Patent Document 2, it is preferable to add alkaline earth metal salt or ammonium salt at the time of rinsing so that elution of the adsorbed substance can be suppressed even after regeneration of the adsorbent.

  Hereinafter, the configuration and effects of the present invention will be described more specifically with reference to examples. However, the present invention is not limited to the following examples.

First, measurement methods used in Examples and Comparative Examples will be described.
(1) Surface average pore diameter of layer of three-dimensional network structure Using a scanning electron microscope, photograph the surface of the hollow fiber membrane at 60,000 times and measure the diameter of 20 arbitrarily selected pore diameters. Then, the number average was obtained.
(2) Retention rate Raw water in which a small module having an effective length of 200 mm made of four hollow fiber membranes was prepared and polystyrene latex particles having an average particle size of 0.309 μm were dispersed under the conditions of a temperature of 25 ° C. and a filtration differential pressure of 16 kPa. Was performed for 30 minutes by external pressure total filtration, the concentration of latex particles in raw water and permeated water was calculated from the ultraviolet absorption coefficient at a wavelength of 234 nm, and the blocking performance was determined from the concentration ratio. A spectrophotometer (U-3200, manufactured by Hitachi, Ltd.) was used to measure the ultraviolet absorption coefficient at a wavelength of 234 nm.
(3) Breaking strength Using a tensile tester (TENSILON (registered trademark) / RTM-100) (manufactured by Toyo Baldwin), a sample with a measurement length of 50 mm was performed five times while changing the sample under the condition of a tensile speed of 50 mm / min. It calculated by calculating | requiring the average value of breaking strength.
(4) Water Permeability Performance A small module having an effective length of 200 mm consisting of four hollow fiber membranes was prepared, and the amount of pure water permeation was measured and converted into pressure (50 kPa) under conditions of a temperature of 25 ° C. and a filtration differential pressure of 16 kPa. Q0, unit = m ³ / m ² / h). Next, a 20 ppm aqueous solution of humic acid (reagent, manufactured by Wako Pure Chemical Industries, Ltd.) was filtered under a pressure differential pressure of 16 kPa and a temperature of 25 ° C. so as to be ² m ³ / m ² by external pressure total filtration. Further, permeated water was supplied for 1 minute at a backwashing pressure of 150 kPa, and the pure water permeation amount immediately after that was measured (Q1).
(5) Fouling resistance A = Q1 / Q0 is used as an index of fouling resistance. The greater the value of A, the better the fouling resistance.
(6) Boron removal performance A small module with an effective length of 200 mm consisting of four hollow fiber membranes was prepared, and seawater collected in Matsuyama, Ehime Prefecture under the conditions of a temperature of 25 ° C. and a filtration differential pressure of 16 kPa was applied by external pressure total filtration. And the boron concentration present in the feed and permeate was measured. An ICP emission spectrometer (P-4010 manufactured by Hitachi, Ltd.) was used for measuring the boron concentration. The boron removal performance was evaluated by the boron removal rate defined by the following formula.
(Boron removal rate) = {1- (boron concentration in permeated water) / (boron concentration in feed water)} × 100
<Example 1>
A powder of cerium hydrated oxide was obtained by using cerium hydroxide (cerium (IV) hydroxide, manufactured by Wako Pure Chemical Industries, Ltd.) at a moisture content of 20% by weight with a low-temperature dryer at 70 ° C.

  18.7 parts by weight of vinylidene fluoride homopolymer having a weight average molecular weight of 420,000 and 69 parts by weight of γ-butyrolactone were mixed and dissolved at 150 ° C. To this resin solution, 12.3 parts by weight of the cerium hydroxide was added while stirring, and the mixture was stirred and mixed to obtain a uniform dispersion. The dispersion was discharged from a double ring mouthpiece with an 85% γ-butyrolactone aqueous solution as a hollow part forming liquid, and solidified in a 6 ° C. bath composed of an 85% by weight γ-butyrolactone aqueous solution. The obtained hollow fiber membrane had a spherical structure and had a structure in which cerium-containing hydrated oxide was retained in the pores.

  Next, on the surface of the hollow fiber membrane, 13% by weight of vinylidene fluoride homopolymer having a weight average molecular weight of 284,000, 5% by weight of polyethylene glycol having a weight average molecular weight of 20,000, 79% by weight of dimethylformamide and water A solution mixed and dissolved at a rate of 3% by weight was uniformly applied. The hollow fiber membrane was immediately immersed in a mixed solvent of 97% by weight of water and 3% by weight of dimethylformamide to solidify the solution. This hollow fiber membrane had a spherical structure holding cerium hydrated oxide on the inside and a three-dimensional network structure on the outside, and the thickness of the three-dimensional network structure was 20 μm. The surface average pore diameter of the three-dimensional network structure was 0.01 μm.

This hollow fiber membrane was found to be excellent in rejection, water permeability, membrane strength, and fouling resistance and exhibit boron removal performance. In particular, it was found that the rejection rate, film strength, fouling resistance, and boron removal performance were excellent.
<Example 2>
A hollow fiber membrane having a spherical structure and containing cerium hydrated oxide was produced in the same manner as in Example 1.

  Next, on the surface of the hollow fiber membrane, 13% by weight of vinylidene fluoride homopolymer having a weight average molecular weight of 284,000, 5% by weight of polyethylene glycol having a weight average molecular weight of 20,000, 79% by weight of dimethylformamide and water A solution mixed and dissolved at a rate of 3% by weight was uniformly applied. The hollow fiber membrane was immediately immersed in a mixed solvent of 95% by weight of water and 5% by weight of dimethylformamide to solidify the solution. This hollow fiber membrane had a spherical structure holding cerium hydrated oxide on the inside and a three-dimensional network structure on the outside, and the thickness of the three-dimensional network structure was 20 μm. The surface average pore diameter of the three-dimensional network structure was 0.02 μm.

This hollow fiber membrane was found to be excellent in rejection, water permeability, membrane strength, and fouling resistance and exhibit boron removal performance. In particular, it was found that the rejection, water permeability, film strength, and boron removal performance were excellent.
<Example 3>
A hollow fiber membrane having a spherical structure and containing cerium hydrated oxide was produced in the same manner as in Example 1.

  Next, on the surface of the hollow fiber membrane, 13% by weight of vinylidene fluoride homopolymer having a weight average molecular weight of 284,000, 10% by weight of polyethylene glycol having a weight average molecular weight of 20,000, 74% by weight of dimethylformamide and water A solution mixed and dissolved at a rate of 3% by weight was uniformly applied. The hollow fiber membrane was immediately immersed in a mixed solvent of 80% by weight of water and 20% by weight of dimethylformamide to solidify the solution. This hollow fiber membrane had a spherical structure holding cerium hydrated oxide on the inside and a three-dimensional network structure on the outside, and the thickness of the three-dimensional network structure was 20 μm. The surface average pore diameter of the three-dimensional network structure was 0.8 μm.

This hollow fiber membrane was found to be excellent in rejection, water permeability, membrane strength, and fouling resistance and exhibit boron removal performance. In particular, it was found that the rejection, water permeability, film strength, and boron removal performance were excellent.
<Example 4>
23.4 parts by weight of cellulose triacetate and 70.1 parts by weight of 2-ethyl 1,3-hexanediol were mixed and dissolved at 180 ° C. To this resin solution, 6.5 parts by weight of cerium hydroxide was added while stirring, and the mixture was stirred and mixed to obtain a uniform dispersion. This dispersion was discharged from a double ring mouthpiece with nitrogen gas as a hollow portion forming gas, and solidified in a water bath at a temperature of 40 ° C. The obtained hollow fiber membrane had a cellular structure and had a structure in which cerium hydrated oxide was retained in the pores.

  Next, a layer having a three-dimensional network structure was formed on the surface of the hollow fiber membrane in the same manner as in Example 2. This hollow fiber membrane had a cell-like structure holding cerium hydrated oxide on the inside and a three-dimensional network structure on the outside, and the thickness of the three-dimensional network structure was 20 μm. The surface average pore diameter of the three-dimensional network structure was 0.02 μm.

This hollow fiber membrane was found to be excellent in rejection, water permeability, membrane strength, and fouling resistance and exhibit boron removal performance.
<Comparative Example 1>
37 parts by weight of vinylidene fluoride homopolymer having a weight average molecular weight of 420,000 and 63 parts by weight of γ-butyrolactone were mixed and dissolved at 150 ° C. The dispersion was discharged from a double ring mouthpiece with an 85% γ-butyrolactone aqueous solution as a hollow part forming liquid, and solidified in a 6 ° C. bath composed of an 85% by weight γ-butyrolactone aqueous solution. The obtained hollow fiber membrane had a spherical structure and had no adsorbent in the pores.

  Next, a layer having a three-dimensional network structure was formed on the surface of the hollow fiber membrane in the same manner as in Example 2. This hollow fiber membrane had a spherical structure having no adsorbent on the inside and a three-dimensional network structure on the outside, and the thickness of the three-dimensional network structure was 20 μm. The surface average pore diameter of the three-dimensional network structure was 0.02 μm.

This hollow fiber membrane did not remove boron.
<Comparative example 2>
A hollow fiber membrane having a spherical structure and containing cerium hydrated oxide was produced in the same manner as in Example 1.

  Next, 15% by weight of vinylidene fluoride homopolymer having a weight average molecular weight of 284,000, 4% by weight of polyethylene glycol having a weight average molecular weight of 20,000, 79% by weight of dimethylformamide, and water are formed on the surface of the hollow fiber membrane. A solution mixed and dissolved at a rate of 2% by weight was uniformly applied. The hollow fiber membrane was immediately immersed in water at 0 ° C. to solidify the solution. This hollow fiber membrane had a spherical structure holding cerium hydrated oxide on the inside and a three-dimensional network structure on the outside, and the thickness of the three-dimensional network structure was 20 μm. Further, the surface pore diameter of the three-dimensional network structure was so small that it could not be observed at 60,000 times using a scanning electron microscope. That is, it was smaller than 0.01 μm.

This hollow fiber membrane was found to be inferior in performance as a separation membrane, with a water permeability of as low as 0.01 m ³ / m ² / hr.
<Comparative Example 3>
A hollow fiber membrane having a spherical structure and containing cerium hydrated oxide was produced in the same manner as in Example 1. This hollow fiber membrane was formed only of a layer having a spherical structure holding cerium hydroxide.

  Next, on the surface of this hollow fiber membrane, vinylidene fluoride homopolymer having a weight average molecular weight of 284,000 is 20% by weight, silicon oxide is 18% by weight, dimethylformamide is 59% by weight, and water is 3% by weight. The mixed and dissolved solution was uniformly applied. The hollow fiber membrane was immediately immersed in a mixed solvent of 95% by weight of water and 5% by weight of dimethylformamide to solidify the solution. Next, the hollow fiber membrane was immersed in a 13% by weight / 80 ° C. aqueous sodium hydroxide solution for 2 hours to extract and remove silicon oxide in the hollow fiber membrane. Further, it was washed with warm water at 90 ° C. for 2 hours. This hollow fiber membrane had a spherical structure holding cerium hydrated oxide on the inside and a three-dimensional network structure on the outside, and the thickness of the three-dimensional network structure was 20 μm. The surface average pore diameter of the three-dimensional network structure was 1.2 μm.

This hollow fiber membrane was found to be inferior in fouling resistance.
<Comparative example 4>
A hollow fiber membrane having a spherical structure and containing cerium hydrated oxide was produced in the same manner as in Example 1. This hollow fiber membrane is composed only of a layer having a spherical structure holding a cerium hydrated oxide, and does not have a layer having a three-dimensional network structure on the outside.

  This hollow fiber membrane was found to be extremely inferior in fouling resistance.

Claims (3)

  A porous layer containing an adsorbent formed from a thermoplastic resin (B) and a layer having a three-dimensional network structure having an average surface pore size of 0.01 μm or more and 1 μm or less formed from the thermoplastic resin (A). A composite separation membrane comprising a layer having a structure.   The composite separation membrane according to claim 1, wherein the adsorbent contains one or more inorganic compounds selected from cerium hydroxide and cerium hydroxide.   The thermoplastic resin (A) and the thermoplastic resin (B) contain polyvinylidene fluoride, and a layer composed of a porous structure containing an adsorbent forms a spherical structure, and the adsorbent is retained in the pores. The composite separation membrane according to claim 1 or 2, wherein