JP2005288266A - Separation membrane, its manufacturing method and water-treating apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a separation membrane having a large flux and an excellent separating function, its manufacturing method and a water-treating apparatus using it. <P>SOLUTION: The membrane consists of a poly-ion-complex composed of a cation polymer and an anion polymer, bonded together, and supported in a laminar form on a water-permeable supporting material, and at least one of the cation and anion polymers is a polymer having a rigid chain structure. The method comprises causing a cation polymer and an anion polymer to be adsorbed alternately by a water-permeable supporting material and has a process of drying the film layer of adsorbed polymers between a process of causing a polymer having one electric charge to be adsorbed and a process of causing a polymer having the other electric charge to be adsorbed. A water-treating apparatus equipped with the membrane is also provided. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a separation membrane, a manufacturing method thereof, and a water treatment apparatus. More specifically, the present invention relates to a separation membrane having a large flux and an excellent separation function, a method for producing the same, and a water treatment apparatus.

Currently, various water treatment techniques are used in the water treatment field, and membrane treatment is an indispensable technique for ultrapure water production and wastewater recovery. When the rate of permeation through the membrane varies from material to material, the mixture can be separated, this property being referred to as the membrane's permselectivity or separation function. Such permselectivity is determined by the interaction between the membrane and the permeating substance. The interaction includes a sieving action by pores and a physicochemical action such as dissolution and diffusion of a substance in the film.
As a separation membrane used for membrane treatment, a microfiltration membrane, an ultrafiltration membrane, a reverse osmosis membrane, or the like is used. In general, in membrane separation, water that has permeated through the membrane is pushed out by applying pressure to remove the separation target in water at the membrane surface to obtain treated water. However, the smaller the separation target, the smaller the membrane. It is necessary to reduce the pore diameter, and high pressure is required to extrude water. For this reason, there is a need for a separation membrane that exhibits a high separation function without extruding water at a low pressure by using another physicochemical action and reducing the flux.
A first charged film having a positive charge that has a dust collection and smoke collection function that can be used in an air cleaner, etc., and that has a hollow structure in which particles, molecules, or ions that can be a source of smoke and odors can enter. And a filter using an alternately adsorbing film formed by alternately adsorbing a second charged film having a negative charge on a substrate, and a filter mechanism for passing water through the filter and the filter A water treatment apparatus has been proposed, and an apparatus for obtaining pure water from saline is disclosed (Patent Document 1). However, in this filter, positively charged particles are adsorbed in the negatively charged film, negatively charged particles are adsorbed in the positively charged film, and the adsorption is due to physical action based on Coulomb force. Once saturated, it is impossible to adsorb any more particles. It has been reported that when a filter that has reached saturation with smoke particles is washed with warm water at 90 ° C for 3 minutes, most of the adsorbed smoke particles are released and the adsorption efficiency is significantly recovered. Long-term use as a membrane is impossible.
JP 2000-334229 A (second page)

  An object of the present invention is to provide a separation membrane having a large flux and an excellent separation function, a method for producing the same, and a water treatment apparatus.

As a result of intensive studies to solve the above-mentioned problems, the present inventors have obtained a separation membrane in which a polyion complex formed by combining a cationic polymer and an anionic polymer is held in a layer on a water-permeable support material. In the present invention, it has been found that the separation function can be improved without lowering the flux by making at least one of the cationic polymer and the anionic polymer a polymer having a rigid linear structure, and the present invention has been completed based on this finding. It came to do.
That is, the present invention
(1) A separation membrane in which a polyion complex formed by combining a cationic polymer and an anionic polymer is held in a layer on a water-permeable support material, and at least one of the cationic polymer and the anionic polymer has a rigid linear structure A separation membrane characterized by being a polymer having,
(2) The separation membrane according to (1), wherein the polymer having a rigid linear structure is DNA,
(3) The separation membrane according to (1), wherein the water-permeable support material has an average pore diameter of 0.1 to 10 μm,
(4) By alternately adsorbing the cationic polymer and the anionic polymer on the water-permeable support material, the polyion complex formed by combining the cationic polymer and the anionic polymer on the water-permeable support material is held in a layered form. A method for producing a separation membrane in which at least one of a cationic polymer and an anionic polymer is a polymer having a rigid linear structure, comprising a step of adsorbing a polymer having one charge and a high charge having the other charge. A method for producing a separation membrane, comprising a step of drying the adsorbed polymer membrane layer between the step of adsorbing molecules,
(5) The separation membrane according to any one of (1) to (3), means for supplying raw water to one side of the separation membrane, and means for taking out treated water from the other side of the separation membrane And a water treatment device characterized by comprising:
(6) In (5), a water treatment apparatus for desalinating by eliminating permeation of soluble substances in raw water by electrostatic repulsion of the separation membrane, wherein the polyion adsorbed on the separation membrane A water treatment apparatus characterized in that after the complex has saturatedly adsorbed ions, treated water having a desalination rate of 10% or more is obtained by continuous water flow;
Is to provide.

  The separation membrane of the present invention is excellent in permselectivity, and by using the separation membrane or water treatment device of the present invention, it is large at a lower pressure than a conventional membrane separation and water treatment device using a reverse osmosis membrane or the like. Flux and high desalination rate can be obtained.

The separation membrane of the present invention is a separation membrane in which a polyion complex formed by combining a cationic polymer and an anionic polymer is held in a layer on a water-permeable support material, and at least one of the cationic polymer and the anionic polymer is It is a separation membrane which is a polymer having a rigid linear structure.
The cationic polymer used in the present invention is not only a polymer having a positive charge with a halide ion or the like as a counter ion, but also reacts with hydrogen halide or the like to form a salt, and can have a positive charge. Polymers are also included. Examples of the cationic polymer used in the present invention include polyethyleneimine, polyvinylamine, polyallylamine, or hydrogen halides thereof, sulfates, nitrates, polyornithine, polylysine and other polyamino acids or salts thereof, and poly (diallyl halide). Dialkylammonium), a condensate of dialkylamine and epihalohydrin, and a polymer formed by addition reaction of N, N, N ′, N′-tetraalkyldiamine and dihalide.
The anionic polymer used in the present invention is not only a polymer having a negative charge with an alkali metal ion or the like as a counter ion, but also forms a salt by reacting with an alkali metal hydroxide or the like to have a negative charge. Also included are polymers that can be Examples of the anionic polymer used in the present invention include polyacrylic acid, polymethacrylic acid, polystyrene sulfonic acid, poly (2-acrylamido-2-methylpropane sulfonic acid), DNA (deoxyribonucleic acid), or alkali metal salts thereof. Can be mentioned.

本発明に用いる剛直鎖構造を有するアニオンポリマーとしては、例えば、ＤＮＡなどを挙げることができる。ＤＮＡは、２本のポリヌクレオチド鎖が共通の中心軸のまわりに螺旋状によじれあっているので、剛直な構造を有する。使用するＤＮＡに特に制限はなく、例えば、サケの精液由来のＤＮＡ、サケの精巣由来のＤＮＡ、ウシの胸腺由来のＤＮＡ、ニシンの精巣由来のＤＮＡなどを挙げることができる。これらの中で、サケの精液又は精巣由来のＤＮＡを好適に用いることができる。サケの卵巣は筋子として、また、サケの卵巣からばらばらに搾り出した卵子はイクラとして重用されているが、ＤＮＡを豊富に含有するサケの精巣は、白子としての需要が少なく、現在はほとんどが産業廃棄物として捨てられている。サケの精巣に多量に含まれるＤＮＡを、機能性高分子材料として利用することは、社会環境的にも大きい意義がある。 In the present invention, a polymer having a rigid linear structure refers to a polymer that cannot be bent as freely in a solution as a random coil. Examples of the polymer having a rigid linear structure include polyisocyanate, aromatic polyamide, double helix DNA, and cellulose derivative. A polymer having a rigid straight chain structure is composed of a chain in which internal rotation is extremely constrained by a hydrogen bond, a conjugated double bond, or the like, a chain connected with a bond angle close to 180 degrees even if the internal rotation is free.
Examples of the cationic polymer having a rigid linear structure used in the present invention include addition reaction of N, N, N ′, N′-tetramethyl-p-phenylenediamine represented by the formula [1] and 1,2-dichloroethane. And the like.

Examples of the anionic polymer having a rigid linear structure used in the present invention include DNA. DNA has a rigid structure because two polynucleotide strands are kinked around a common central axis. The DNA to be used is not particularly limited, and examples thereof include salmon semen-derived DNA, salmon testis-derived DNA, bovine thymus-derived DNA, and herring testis-derived DNA. Among these, salmon semen or testis-derived DNA can be preferably used. Salmon ovaries are used as muscles, and eggs squeezed from salmon ovaries are used as salmon roe. Salmon testes, which contain abundant DNA, have little demand for white eggs, and most of them are now industrial. It is thrown away as waste. The use of a large amount of DNA contained in the salmon testis as a functional polymer material has great social and environmental significance.

  The water-permeable support material used in the present invention preferably has an average pore diameter of 0.1 to 10 μm, and more preferably 0.2 to 5 μm. If the average pore diameter is less than 0.1 μm, the flux of the separation membrane may be too small. When the average pore diameter exceeds 10 μm, the separation function of the separation membrane may be deteriorated. Although there is no restriction | limiting in particular in the thickness of the water-permeable support material used for this invention, It is preferable that it is 0.01-1 mm, and it is more preferable that it is 0.05-0.5 mm. The material of the water-permeable support material used in the present invention is not particularly limited. For example, cellulose acetate, cellulose triacetate, nitrocellulose, regenerated cellulose, gelatin, aromatic polyamide, acrylonitrile-vinyl chloride copolymer, polysulfone, polycarbonate, polyester , Polytetrafluoroethylene, polyvinylidene fluoride, polypropylene and the like. There is no restriction | limiting in particular in the shape of a water-permeable support material, For example, a plane membrane, a spiral, a pipe type, a hollow fiber etc. can be mentioned. The tube type, hollow fiber, etc. are preferably used as an external pressure type separation membrane by laminating a polymer membrane layer on the outside thereof.

In the method for producing a separation membrane of the present invention, the cationic polymer and the anionic polymer are alternately adsorbed on the water-permeable support material, whereby the cationic polymer and the anionic polymer are combined on the water-permeable support material. A method for producing a separation membrane in which a polyion complex is held in a layer and at least one of a cationic polymer and an anionic polymer is a polymer having a rigid linear structure, the method comprising the step of adsorbing one charged polymer And a step of drying the adsorbed polymer film layer between the step of adsorbing the other charged polymer.
In the method of the present invention, there is no particular limitation on the method of adsorbing a polymer having a positive charge or a negative charge on the water permeable support material. For example, after the surface of the water permeable support material is positively or negatively charged. The first polymer membrane layer is formed by adsorbing the polymer having a negative or positive charge on the surface of the hydrophobic support material by contacting with a polymer aqueous solution having a charge different from that of the charged charge. be able to. After forming a polymer film layer having a negative or positive charge, it is preferable to wash the polymer film layer using pure water or the like. If the polymer film layer is not washed, the polymer that has not been tightly taken into the polymer film layer remains on the surface of the polymer film layer, which hinders the formation of a dense polymer film layer by drying.

In the method of the present invention, a step of drying the adsorbed polymer film layer is provided between the step of adsorbing the polymer having one charge and the step of adsorbing the polymer having the other charge. There is no restriction | limiting in particular in the embodiment of a drying process, For example, a polymer film layer can be dried by applying 50-90 degreeC warm air for 1 to 10 minutes. Since the polymer film layer is thin, it can be easily dried under mild conditions. Without adsorbing the adsorbed polymer film layer, when adsorbing a polymer having a charge with a different sign, the polymer film layer is laminated while containing moisture, and finally when moisture is removed and dried, There is a possibility that a place where moisture exists becomes a void, and a laminated polymer film layer has a sparse structure. In addition, since the polymer in the polymer film layer containing moisture is easier to move than the polymer in the dried polymer film layer, at the boundary of the polymer film layer composed of polymers having different signs of charges. The polymer having a positive charge and the polymer having a negative charge may be entangled to form a polymer having lost ionicity. By drying the adsorbed polymer film layer, a dense polymer film layer is formed.
In the method of the present invention, there is no particular limitation on the number of polymer film layers composed of the cationic polymer and the polymer film layer composed of the anion polymer, but the number of each polymer film layer is 1 to 30 in total. The number of polymer film layers is preferably 3 to 20 layers, and more preferably 6 to 40 layers in total. Although there is no restriction | limiting in particular in the thickness of each polymer film layer, It is preferable that it is 0.1-20 nm, and it is more preferable that it is 3-12 nm.
The separation membrane of the present invention is not particularly limited to the above production method. For example, the cationic polymer and the anionic polymer are adsorbed or held on the water-permeable support material by adsorbing or holding the cationic polymer and the anion polymer in a mixed state. Alternatively, a polyion complex layer in which and are uniformly dispersed may be held in a layer shape. In this case, for example, the polyion complex layer is formed by immersing the water-permeable support material in a solution obtained by mixing a cationic polymer aqueous solution and an anionic polymer aqueous solution.
In the separation membrane obtained by such a method, the thickness and the number of layers of the polyion complex layer are not particularly limited, but the number of polyion complex layers is 10 to 100 layers, and the total layer thickness is about 100 to 1,000 nm. Preferably there is.

  In the present invention, at least one of a cationic polymer and an anionic polymer that form a polyion complex held in a layered form on a hydrophobic support material is a polymer having a rigid linear structure. The polymer having a rigid linear structure is adsorbed or held in the pores of the water-permeable support material in a state where a bridge is bridged at the opening of the pore. When a polymer bridge having a rigid linear structure is formed at the opening of the pore, the polymer adsorbed or retained thereafter is caught by the polymer bridge having the rigid linear structure and enters the inside of the pore. do not do. FIG. 1 is a schematic cross-sectional view of one embodiment of the separation membrane of the present invention. In this embodiment, since the polymer that is first adsorbed on the hydrophobic support material is the polymer 1 that does not have a rigid linear structure, the polymer penetrates into the pores 3 of the hydrophobic support material 2, It is also adsorbed on the inner surface. Next, the polymer having the electric charge of the opposite sign that is adsorbed is the polymer 4 having a rigid structure, and therefore bridges the opening 5 of the pore and does not enter the inside of the pore. The polymer having no rigid structure that is adsorbed third is also caught by the polymer having a rigid structure with a bridge, and does not penetrate into the pores. Since the polymer adsorbed inside the pore does not contribute to the separation function, according to the present invention, the amount of the polymer having positive or negative charge adsorbed inside the pore is reduced and used. Molecules can be used effectively. In addition, when a polymer is adsorbed inside the pore, the effective diameter of the pore is reduced and the flux is lowered, but the amount of the polymer adsorbed inside the pore is reduced by the method of the present invention. By this, the pore diameter which a water-permeable support material originally has can be maintained, and the fall of a flux can be prevented.

In the present invention, adsorption or retention of a polymer having a rigid linear structure on the hydrophobic support material is limited to only the first few layers, and only the polymer membrane layer close to the water-permeable support material has a high linear structure. A polymer film layer made of molecules can be used, and thereafter, a polymer film layer made of a polymer having no rigid linear structure can be used.
In the separation membrane of the present invention, polyion complexes formed by combining a cationic polymer and an anionic polymer are laminated in layers. The positively charged particles or the negatively charged particles in water are repelled by the Coulomb force of the separation membrane of the present invention and are prevented from passing through the separation membrane, so that a high desalting rate can be expressed. Further, since the structure of the polymer film layer is dense, a high blocking effect can be obtained even for fine particles that are not charged.
Next, a water treatment apparatus using the separation membrane of the present invention will be described with reference to FIG.
FIG. 3 is a schematic sectional view showing an embodiment of the water treatment apparatus of the present invention.
In this water treatment apparatus, partition plates 11 and 12 are provided at both ends in a container (vessel) 10, and a raw water chamber 13 and a treated water chamber 14 are formed. A hollow tubular separation membrane element 20 is suspended between the partition plates 11 and 12 in the raw water chamber 13. One partition plate 12 is provided with an opening 12 </ b> A, one end of the separation membrane element 20 is attached to the opening 12 </ b> A, and the inside of the hollow tube of the separation membrane element 20 communicates with the treated water chamber 14. 15 is an inlet for raw water, 16 is an outlet for concentrated water, and 17 is an outlet for treated water.
The raw water introduced into the water treatment apparatus from the introduction port 15 flows, for example, on the polymer membrane layer of the separation membrane shown in FIG. 1 in a cross flow manner, and passes in the polymer membrane lamination direction of the separation membrane element 20. In the meantime, ions and SS are removed. The treated water that has passed through the polymer membrane layer is taken out from the treated water outlet 17 through the treated water chamber 14 from the hollow portion of the separation membrane element 20. On the other hand, the concentrated water enriched with ions and SS excluded by the membrane is taken out from the concentrated water outlet 16. If necessary, a part of this concentrated water may be returned to the raw water introduction side and circulated, and the remaining part may be taken out of the system.
FIG. 3 shows a water treatment apparatus provided with a hollow tubular separation membrane element 20, but there is no particular limitation on the type of the separation membrane of the water treatment apparatus of the present invention, and even a hollow fiber membrane is a flat membrane. It may be. A hollow fiber membrane is preferable in terms of ensuring a large surface area of the membrane per unit volume. Either type of membrane is housed in a container, preferably a pressurized water supply type that pressurizes raw water and supplies it to the container, but the separation membrane is immersed in open water and the treated water side is depressurized. An immersion type for obtaining treated water may be used. There is no restriction | limiting in particular also about the grade of the feed water pressure and pressure reduction at this time, and it determines suitably so that a desired amount of treated water may be obtained through a film | membrane. Further, the flat membrane may be used in a plate and frame type or in a spiral type. These membrane types and device types are the same as those in the microfiltration membrane device, ultrafiltration membrane device, and reverse osmosis membrane device, and the water treatment device of the present invention can be assembled by diverting those known techniques. it can.
There is no particular restriction on the water flow method to the separation membrane, and both the cross flow (parallel flow filtration) method and the dead end method can be applied. However, the dead end method may clog the membrane. It is preferable to adopt a cross flow method.
In the water treatment apparatus of the present invention, since deionization is performed by a repulsive action by Coulomb force, it is preferable to perform the treatment by continuously supplying raw water and continuously discharging the treated water. Therefore, when the surface of the separation membrane is contaminated with SS components and the like due to long-term continuous water flow, and the water flow resistance rises to a predetermined value or more, it is desirable to perform membrane surface cleaning.
When the water treatment apparatus of the present invention is used as a desalination apparatus, the separation membrane is designed so that a desalination rate of 10% or more, preferably 50% or more, more preferably 70% or more is obtained in continuous water flow. Therefore, the number and thickness of the polymer membranes of the separation membrane may be changed. Further, a denser and smaller pore size separation membrane can be employed to provide a device with a high desalting rate.
The separation membrane of the present invention has a deionizing effect by preventing the passage of ions in water by the repulsive action of the Coulomb force of the polyion complex layer laminated on the water permeable support material. Compared to an osmotic membrane or the like, the pore diameter can be increased and / or the film thickness can be decreased. As a result, it is possible to provide a separation membrane and a water treatment apparatus that reduce the treatment pressure while maintaining a high desalination rate and improve the flux.

Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples.
Example 1
Microfiltration membrane [Nippon Millipore Corporation, membrane filter, HAWP04700, flat membrane, pore diameter 0.45 μm, diameter 47 mm] as water-permeable support material, and water of poly-N-vinylformamide as a positively charged polymer Separation using polyvinylamine hydrochloride with a weight average molecular weight of 3.7 million obtained by decomposition, DNA having a rigid linear structure [manufactured by Wako Pure Chemical Industries, Ltd., salmon semen] as a negatively charged polymer A membrane was prepared.
The polymer was placed on the support plate 7 of the membrane fixing container 6 shown in FIG. A 1.5 g / L aqueous solution of polyvinylamine hydrochloride is poured into a container, allowed to stand for 1 minute, the polyvinylamine hydrochloride is adsorbed on the surface of the microfiltration membrane, discharged, and the membrane surface is washed with pure water. Then, it was dried by sending warm air for 5 minutes with a dryer. Next, a 1 g / L aqueous solution of DNA was poured into the container, allowed to stand for 1 minute to adsorb the DNA, and then discharged. The membrane surface was washed with pure water and dried by sending warm air for 5 minutes with a dryer. . Furthermore, the adsorption of polyvinylamine hydrochloride and the adsorption of DNA were alternately repeated four times, thereby obtaining a separation membrane in which 10 polymer membrane layers were laminated in total.
The obtained separation membrane was attached to a small-diameter flat membrane cell of a flat membrane test apparatus, and the desalting performance was evaluated. A 1 g / L aqueous solution of magnesium sulfate was used as sample water, introduced into the cell at a flow rate of 1.4 mL / min and a pressure of 0.45 MPa, and allowed to pass through for 4 hours.
The electric conductivity of the permeated water is 511 μS / cm, the electric conductivity of the concentrated water is 852 μS / cm, and (1− (the electric conductivity of the permeated water / the electric conductivity of the concentrated water)) × 100 (%) The desalting rate determined as was 40%. The flux after 4 hours was 0.525 m / day, and the flux converted to 1.2 MPa was 1.40 m / day.
Example 2
In the same manner as in Example 1, the adsorption of polyvinylamine hydrochloride and the adsorption of DNA were alternately repeated 8 times each to obtain a separation membrane in which a total of 16 polymer membrane layers were laminated.
The desalting performance of the obtained separation membrane was evaluated in the same manner as in Example 1 except that the test water pressure was 0.69 MPa. The electric conductivity of the permeated water was 394 μS / cm, the electric conductivity of the concentrated water was 839 μS / cm, and the desalting rate was 53%. The flux converted to 1.2 MPa after 4 hours was 1.22 m / day.
Example 3
In the same manner as in Example 1, the adsorption of polyvinylamine hydrochloride and the adsorption of DNA were alternately repeated 10 times each to obtain a separation membrane in which a total of 20 polymer membrane layers were laminated.
The desalting performance of the obtained separation membrane was evaluated in the same manner as in Example 1, except that the test water pressure was 1.2 MPa. The electric conductivity of the permeated water was 268 μS / cm, the electric conductivity of the concentrated water was 893 μS / cm, and the desalting rate was 70%. The flux after 4 hours was 0.78 m / day.

Comparative Example 1
In the same manner as in Example 1 except that sodium polystyrene sulfonate [Tosoh Corporation, trade name: PS-100, weight average molecular weight: 1 million] was used instead of DNA as a polymer having a negative charge. The adsorption of polyvinylamine hydrochloride and the adsorption of DNA were alternately repeated 5 times each to obtain a separation membrane in which 10 polymer membrane layers were laminated in total.
The obtained separation membrane was attached to a small-diameter flat membrane cell of a flat membrane test apparatus, and the desalting performance was evaluated. A 1 g / L aqueous solution of magnesium sulfate was used as sample water, introduced into the cell at a flow rate of 1.4 mL / min and a pressure of 0.06 MPa, and allowed to pass through for 4 hours.
The electric conductivity of the permeated water was 784 μS / cm, the electric conductivity of the concentrated water was 792 μS / cm, and the desalting rate was 1%. The flux after 4 hours was 0.54 m / day, and the flux converted to 1.2 MPa was 10.8 m / day.
Comparative Example 2
In the same manner as in Comparative Example 1, adsorption of polyvinylamine hydrochloride and adsorption of sodium polystyrene sulfonate were alternately repeated 8 times to obtain a separation membrane in which a total of 16 polymer membrane layers were laminated.
The desalting performance of the obtained separation membrane was evaluated in the same manner as in Example 1 except that the pressure of the test water was 0.08 MPa. The electric conductivity of the permeated water was 732 μS / cm, the electric conductivity of the concentrated water was 755 μS / cm, and the desalting rate was 3%. The flux converted to 1.2 MPa after 4 hours was 12.6 m / day.
Comparative Example 3
In the same manner as in Comparative Example 1, adsorption of polyvinylamine hydrochloride and adsorption of sodium polystyrene sulfonate were alternately repeated 10 times to obtain a separation membrane in which 20 polymer membrane layers were laminated in total.
The desalting performance of the obtained separation membrane was evaluated in the same manner as in Example 1 except that the test water pressure was 0.1 MPa. The electric conductivity of the permeated water was 755 μS / cm, the electric conductivity of the concentrated water was 763 μS / cm, and the desalting rate was 3%. The flux converted to 1.2 MPa after 4 hours was 8.5 m / day.
The results of Examples 1 to 3 and Comparative Examples 1 to 3 are shown in Table 1.

As can be seen in Table 1, a polymer membrane layer composed of polyvinylamine hydrochloride having a positive charge and a polymer membrane layer composed of DNA having a rigid linear structure having a negative charge alternately The separation membranes of Examples 1 to 3 laminated on top have water permeability of 1.2 MPa equivalent flux 0.78 to 1.40 m / day. The desalination rate is 40% of the separation membrane of Example 1 in which five layers of positively charged polymer membranes and five layers of negatively charged polymer membranes are alternately stacked, and the polymer membrane having positive charges. The desalination rate is improved as the number of layers increases up to 70% of the separation membrane of Example 3 in which 10 layers and 10 polymer membranes having negative charges are alternately laminated.
In contrast, the membranes of Comparative Examples 1 to 3 using sodium polystyrene sulfonate having no rigid linear structure as a negatively charged polymer have a 1.2 MPa equivalent flux of 8.5 to 12.6 m. Although it is large as / day, the desalting rate is 1 to 3% and hardly shows a separation function.
Since the membranes of Comparative Examples 1 to 3 have a large pore size, it is considered that they do not have a blocking effect on magnesium ions and sulfate ions. In the separation membranes of Examples 1 to 3, the DNA having a rigid linear structure is bridged on the pores of the microfiltration membrane, and a polymer membrane layer having a dense structure is formed thereon. It is estimated that the separation membrane has a good balance between rate and flux.

  The separation membrane of the present invention comprises a polymer membrane layer made of a polymer having a positive charge and a polymer membrane layer made of a polymer having a negative charge alternately laminated on a water-permeable support material. Since one polymer has a rigid linear structure, it becomes a separation membrane having a fine structure with a small pore size, a good balance between flux and desalination rate, and an excellent separation function. According to the method of the present invention, a separation membrane having such a structure can be easily produced.

It is a typical sectional view of one mode of a separation membrane manufactured by the method of the present invention. It is explanatory drawing of the instrument used in the Example. It is a rough sectional view showing an embodiment of a water treatment equipment of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Polymer which does not have rigid linear structure 2 Hydrophobic support material 3 Pore 4 Polymer which has rigid structure 5 Opening 6 Membrane fixed container 7 Support plate 8 Microfiltration membrane 9 Support rod 10 Container (vessel)
DESCRIPTION OF SYMBOLS 11 Partition plate 12 Partition plate 12A Opening 13 Raw water chamber 14 Treated water chamber 15 Raw water inlet 16 Concentrated water outlet 17 Treated water outlet 20 Separation membrane element

Claims (6)

  A separation membrane in which a polyion complex formed by combining a cationic polymer and an anionic polymer is held in a layer on a water-permeable support material, wherein at least one of the cationic polymer and the anionic polymer has a rigid linear structure A separation membrane characterized by   The separation membrane according to claim 1, wherein the polymer having a rigid linear structure is DNA.   The separation membrane according to claim 1, wherein the water-permeable support material has an average pore diameter of 0.1 to 10 μm.   By alternately adsorbing the cation polymer and the anion polymer on the water permeable support material, the polyion complex formed by combining the cation polymer and the anion polymer on the water permeable support material is held in a layer, A method for producing a separation membrane in which at least one of a cationic polymer and an anionic polymer is a polymer having a rigid linear structure, the step of adsorbing a polymer having one charge and the adsorption of a polymer having the other charge A method for producing a separation membrane, comprising a step of drying the adsorbed polymer membrane layer between the step of causing the polymer membrane to be adsorbed.   A separation membrane according to any one of claims 1 to 3, comprising means for supplying raw water to one side of the separation membrane, and means for taking out treated water from the other side of the separation membrane. The water treatment apparatus characterized by the above-mentioned.   6. The water treatment apparatus according to claim 5, wherein the separation membrane removes permeation of soluble substances in the raw water by electrostatic repulsion of the separation membrane, wherein the polyion complex adsorbed on the separation membrane is an ion. A water treatment apparatus characterized in that treated water having a desalination rate of 10% or more is obtained by continuous water passage after saturated adsorption.

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