JP2017080689A - Separation membrane for bubble liquid concentration, membrane element and membrane module - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a separation membrane for bubble liquid concentration capable of obtaining high-concentration bubble-containing liquid by suppressing disappearance of bubbles by contact with the membrane during bubble liquid concentration, and to provide a membrane element using the same, and a membrane module including the same.SOLUTION: A separation membrane for bubble liquid concentration in which a bubble contact angle in water is 140° or more at least on one surface is preferably used when concentrating bubble liquid with a diameter below 1 μm existing in the liquid.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a separation membrane for concentrating bubble liquid that can be used for concentrating bubble liquid present in a liquid, a membrane element using the same, and a membrane module including the same, and in particular, having a diameter of less than 1 μm present in the liquid. This is useful as a technique for concentrating bubbles (ultra fine bubbles, UFB).

  In recent years, research on technologies for generating water containing ultrafine bubbles that are stable over a long period of time has been actively conducted. For example, Non-Patent Document 1 discloses an apparatus that generates a large amount of ultrafine bubbles. Moreover, in the nonpatent literature 2, it is reported about the ultra fine bubble stably existing in water.

  In addition, there are various methods for generating ultra fine bubbles. For example, in the fine bubble generating device of Patent Document 1, a mixed fluid in which a gas and a liquid are mixed in a fluid swirl chamber is swirled at a high speed. Bubbles are refined by the shearing force generated in the swirling flow.

  However, since water containing ultrafine bubbles is generated by mechanically mixing water and air, the amount of fine bubbles generated is about 10 million / mL to 1 billion / mL. In order to study the use of liquids containing fine bubbles and to improve the efficiency of handling liquids containing fine bubbles, it is important to increase the density of fine bubbles.

  For this reason, Patent Document 2 discloses that a part of the liquid containing fine bubbles is transmitted through a filtration filter that does not pass fine bubbles having a diameter larger than 200 nm for the purpose of easily generating a liquid having a high density of fine bubbles. And a method for producing a high-density microbubble liquid that obtains a high-density microbubble liquid that is the remainder of the liquid is disclosed. However, Patent Document 2 mentions the pore diameter of the filter, but does not disclose the material or the like.

Japanese Patent No. 4129290 JP 2014-155920 A

“FZ1N-02 nanobubble generator” catalog, [online], May 23, 2011, IDEC Corporation, [searched on December 20, 2011], Internet <URL: http://www.idec.com/ jpja / products / dldata / pdf_b / P1383-0.pdf> Koichi Terasaka and 5 others, “Examination of analysis method of nanobubbles generated by gas-liquid mixed shearing method”, Proceedings of Annual Meeting 2011 of Multiphase Flow Society of Japan, Annual Meeting of Japanese Society of Multiphase Flow 2011 (Kyoto) Committee, August 2011, P424-425

  However, when a filtration filter usually used as a separation membrane is used as in the high-density fine bubble liquid generation method of Patent Document 2, bubbles are likely to disappear due to contact with the membrane when the bubble liquid is concentrated. The total amount of bubbles after concentration was found to be significantly reduced relative to the total amount of bubbles in the supplied liquid. For example, as will be described later, when a polysulfone UF membrane that is widely used as a separation membrane is used (see Comparative Example 1), even if the stock solution is concentrated 10 times, most bubbles disappear, There was a problem that a bubble-containing liquid having a concentration could not be obtained.

  Accordingly, an object of the present invention is to provide a separation membrane for concentrating bubble liquid that can obtain a high-concentration bubble-containing liquid, a membrane element using the same, and a membrane module including the same.

  As a result of intensive studies on the material and surface characteristics of the membrane used for concentrating the bubble liquid, the present inventors have found that the contact angle formed between the surface of the separation membrane and the tangential direction of the bubble in water (hereinafter referred to as the bubble contact angle). It was found that the above-mentioned object can be achieved by using a separation membrane having an angle of 140 ° or more, and the present invention has been completed.

  That is, the bubble liquid concentration separation membrane of the present invention is characterized in that the bubble contact angle in water is 140 ° or more on at least one surface.

  According to the separation membrane for concentrating bubble liquid of the present invention, since the bubble contact angle on the surface of the separation membrane is 140 ° or more, it becomes difficult for bubbles to adhere to the membrane surface. That is, as shown in FIG. 1, in the case of the bubble contact angle in water of 104 ° (FIG. 1a) and in the case of bubble contact angle of 167 ° (FIG. 1c), the state of bubble attachment is large, and the latter is more It is thought that bubbles can be suppressed from disappearing by making bubbles less likely to adhere to the film surface. As a result, it is possible to suppress the disappearance of bubbles due to contact with the membrane during the bubble liquid concentration, and a high-concentration bubble-containing liquid can be obtained.

  In particular, the separation membrane for concentrating bubble liquid of the present invention is preferably used when concentrating a fine bubble liquid having a diameter of less than 1 μm present in the liquid. When the bubble contact angle on the surface of the separation membrane is 140 ° or more, it is possible to make it difficult to attach bubbles to the membrane surface even for fine bubbles having a diameter of less than 1 μm, and to efficiently separate and concentrate the bubbles. it can.

  In the above, it is preferable that the one surface has a porous structure or a non-porous structure having an average pore diameter of 1,000 nm or less. With such an average pore diameter, bubbles having a diameter of less than 1 μm can be efficiently separated and concentrated.

  Moreover, it is preferable to have a polymer porous layer or non-porous layer having hydrophilicity on the one surface. By having a polymer porous layer or non-porous layer having hydrophilicity, a separation membrane having a bubble contact angle in water of 140 ° or more is easily obtained.

  It is preferable that the polymer porous layer or the non-porous layer has been subjected to a hydrophilic treatment by a hydrophilic substance coating or a hydrophilic polymer graft. By such a method, the surface of the porous polymer layer can be more reliably made to have a bubble contact angle of 140 ° or more in water by a simple operation.

  On the other hand, the membrane element of the present invention is characterized by comprising the separation membrane for concentrating bubble liquid described above. According to the membrane element of the present invention, since it is provided with the separation membrane for concentrating bubble liquid of the present invention, it is possible to suppress the disappearance of bubbles due to contact with the membrane during the concentration of bubble liquid, thereby obtaining a highly concentrated bubble-containing liquid. be able to.

  On the other hand, the membrane module of the present invention includes the membrane element described above and a container that accommodates the membrane element and forms a concentration-side channel and a permeation-side channel. It is possible to obtain a high-concentration bubble-containing liquid by suppressing the disappearance of bubbles due to contact.

  Note that when the bubble-containing liquid is generated, bubbles having a diameter of 1 μm or more to 500 nm or less may be included. Therefore, the concentrated bubble-containing liquid may contain bubbles having a diameter of 1 μm or more. Good.

It is a photograph for explaining the bubble contact angle in water, and shows a case where (a) is a bubble contact angle of 104 °, (b) is a bubble contact angle of 135 °, and (c) is a bubble contact angle of 167 °. It is a disassembled perspective view which shows an example of the membrane element of this invention. It is a longitudinal cross-sectional view which shows an example of the membrane module of this invention. It is a longitudinal cross-sectional view which shows the other example of the membrane module of this invention. It is a schematic block diagram which shows an example of the usage condition of the membrane module of this invention. It is a schematic block diagram which shows the other example of the usage pattern of the membrane module of this invention.

(Separation membrane for bubble liquid concentration)
The separation membrane for concentrating bubble liquid according to the present invention is used when concentrating a bubble liquid present in a liquid, for example, having a diameter of less than 100 μm, and particularly concentrating bubble liquid having a diameter of less than 1 μm present in a liquid. It is preferable to use it.

  Bubbles with a diameter of less than 1 μm present in the liquid are called ultra fine bubbles (UFB), and have a property that the liquid is stable over a long period of time and the liquid is transparent as compared with a microvalve having a larger diameter.

  UFB has characteristics such as gas enrichment, surface activity, crushing, electrification, increase in specific surface area, etc., and can perform single wafer peeling, emulsification, fragrance encapsulation, freshness maintenance, and the like. For this reason, UFB is used for semiconductor devices, flat panel displays, electronic devices, solar cells, secondary batteries, food, beverages, cosmetics, medicines, medicine, plant cultivation, new functional materials, removal of radioactive substances, etc. It can be used for various purposes.

  UFB can be generated by various methods. For example, a mixed fluid in which a gas and a liquid are mixed in a fluid swirl chamber is swirled at high speed, and bubbles are refined by shearing force generated in the swirl flow. A method is mentioned.

  Examples of the liquid having bubbles include water, an alcohol aqueous solution, ozone water, an acidic aqueous solution, an alkaline aqueous solution, and a surfactant aqueous solution.

  The average diameter of UFB is usually less than 1 μm and preferably 0.01 to 0.5 μm from the viewpoint of developing the above functions. In addition, the number density in the liquid before concentration is preferably at least 10 million / mL, and is preferably at least 10 million / mL to 1 billion / mL from the viewpoint of increasing the number density after concentration. More preferred.

  The separation membrane for concentrating bubble liquid according to the present invention is characterized in that at least one surface has a bubble contact angle in water of 140 ° or more, but both surfaces may have a bubble contact angle of 140 ° or more. . When only one surface has a bubble contact angle of 140 ° or more, the surface is disposed on the stock solution side (liquid before concentration), and disposed on the permeate side from the other surface.

  The bubble contact angle in water is 140 ° or more and less than 180 °, but it is preferably 145 ° or more and 150 ° from the viewpoint of more reliably suppressing the disappearance of bubbles due to contact with the membrane during bubble liquid concentration. The above is more preferable, and 160 or more is most preferable. In addition, the bubble contact angle in water is preferably 178 ° or less, more preferably 175 ° or less, and most preferably 170 ° or less from the viewpoint of ease of production of the separation membrane.

  The separation membrane having such a bubble contact angle can be obtained by a method of hydrophilizing at least the surface of the hydrophobic polymer porous layer, or by producing a separation membrane with a hydrophilic polymer.

  When the separation membrane is produced with a hydrophilic polymer like the latter, for example, by using a cellulose resin, a polyamide resin, a polyvinyl alcohol resin, an epoxy resin, or by introducing a crosslinked structure, A separation membrane having a bubble contact angle of can be obtained. Such a separation membrane is preferably one in which a hydrophilic polymer porous layer is formed on one side of a nonwoven fabric layer from the viewpoint of durability, pressure resistance, permeation flow rate, etc. of the separation membrane. In the present invention, not only a flat membrane but also a hollow fiber membrane and a tubular membrane can be used.

  However, from the viewpoint of the durability and manufacturability of the separation membrane, a method of hydrophilizing the surface of the hydrophobic polymer porous layer is preferable. In particular, it is preferable that the hydrophilic treatment is performed by coating with a hydrophilic substance or grafting with a hydrophilic polymer.

  Examples of the separation membrane used for the hydrophilization treatment include those having a hydrophobic polymer porous layer. From the viewpoint of the durability of the separation membrane, pressure resistance, permeation flow rate, etc., the polymer porous layer is one side of the nonwoven fabric layer. What is formed in is preferable. In the present invention, not only a flat membrane but also a hollow fiber membrane and a tubular membrane can be used.

  Examples of the hydrophobic polymer include various polymers such as polysulfone and polyarylethersulfone exemplified by polyethersulfone, polyimide, polyvinylidene fluoride, epoxy resin, polyethylene, polypropylene, and fluororesin. In particular, polysulfone and polyarylethersulfone are preferable because they are chemically, mechanically and thermally stable.

  The separation membrane used for the hydrophilization treatment may be an asymmetric membrane having a different average pore size on both sides of the membrane or a symmetric membrane, but is preferably an asymmetric membrane from the viewpoint of treatment efficiency during concentration. .

  The average pore size of the separation membrane (the average pore size of the surface having the smaller pore size) is preferably 0.001 to 2 μm from the viewpoint of the pore size after the hydrophilic treatment, the ease of the hydrophilic treatment, and the like. 1 micrometer is more preferable and 0.01-0.4 micrometer is still more preferable.

10-300 micrometers is preferable and, as for the thickness of a separation membrane or a polymer porous layer, 50-200 micrometers is more preferable. As for the thickness of a nonwoven fabric layer, 30-200 micrometers is preferable,
50-150 micrometers is more preferable.

The nonwoven fabric layer is not particularly limited as long as it provides an appropriate mechanical strength while maintaining the separation performance and permeation performance of the separation membrane, and a commercially available nonwoven fabric can be used. As this material, for example, a material made of polyolefin, polyester, cellulose or the like is used, and a material in which a plurality of materials are mixed can also be used. In particular, it is preferable to use polyester in terms of moldability. In addition, a long fiber nonwoven fabric or a short fiber nonwoven fabric can be used as appropriate, but a long fiber nonwoven fabric can be preferably used from the viewpoint of fine fuzz that causes pinhole defects and uniformity of the film surface. In addition, the air permeability of the nonwoven fabric layer at this time is not limited to this, but can be about 0.5 to 10 cm ³ / cm ² · s, and 1 to ⁵ cm ³ / Those having a size of about cm ² · s are preferably used.

  Various separation membranes as described above are commercially available, and hydrophilic polymer separation membranes can be used as they are. In addition, the hydrophobic polymer separation membrane can be used for hydrophilization treatment. It is also possible to manufacture the separation membrane by a known method.

  The production method when the polymer of the polymer porous layer is polysulfone will be exemplified. The polymer separation membrane can be produced by a method generally called a wet method or a dry wet method. First, a solution preparation step in which polysulfone, a solvent and various additives are dissolved, a coating step in which the nonwoven fabric is coated with the solution, a drying step in which the solvent in the solution is evaporated to cause microphase separation, a water bath, etc. The polymer porous layer on the nonwoven fabric can be formed through an immobilization step of immobilization by dipping in a coagulation bath. The thickness of the polymer porous layer can be set by adjusting the solution concentration and the coating amount after calculating the ratio of impregnation into the nonwoven fabric layer.

  Next, the hydrophilic treatment will be described. The hydrophilization treatment is preferably performed by hydrophilic substance coating or hydrophilic polymer grafting. In addition, surface treatment by introduction of hydrophilic groups, plasma treatment, excimer laser irradiation, surface treatment by corona discharge treatment, The hydrophilization treatment is possible also by the above.

  There are two methods for coating a hydrophilic substance: a method using a low molecule as a hydrophilic substance and a method using a polymer, but it is also possible to polymerize by performing a polymerization reaction using a low molecule.

  As a method using a polymer, a polymer such as polyvinyl alcohol, polyethylene glycol, polyvinyl pyrrolidone, polyacrylic acid, hydroxypropyl cellulose, etc. is dissolved in a solvent, and the solution is applied or impregnated on a separation membrane. The method of making it dry is mentioned. In that case, it is also possible to carry out a crosslinking reaction between the polymers or the separation membrane using a crosslinking agent or the like.

  In addition, even in the method using a low molecule as a hydrophilic substance, polyhydric alcohols such as sucrose fatty acid ester, sorbitol and glycerin, surfactants such as sodium dodecylbenzenesulfonate, sodium dodecylsulfate and sodium laurylsulfate, sodium lactate And a method of dissolving in a solvent using glycerin or the like, applying or impregnating the solution to a separation membrane, and then drying.

  It is also possible to use a hydrophilic substance having a functional group having reactivity with the separation membrane to cause a reaction between the separation membranes.

  When grafting a hydrophilic polymer, for example, a vinyl type hydrophilic monomer is used. As the vinyl type hydrophilic monomer, acrylic acid, methacrylic acid, hydroxymethyl methacrylic acid, sulfoethyl methacrylic acid, styrene sulfonic acid or alkali metal salts thereof can be used.

  When grafting is performed, it is preferable to perform electron beam irradiation on the separation membrane, chemical graft polymerization using an initiator, photoinitiated graft polymerization, or the like. In addition, after the polymerization is completed, excess monomer is removed.

  As a method of coating by carrying out a polymerization reaction using a low molecule, a method of carrying out a polymerization reaction using a vinyl type hydrophilic monomer used for grafting, a polymerization initiator, and a crosslinking agent if necessary, Alternatively, a method using interfacial polymerization as described below can be used.

  In the method using interfacial polymerization, for example, a polyamide-based coat layer is formed, and generally a homogeneous film having no visible pores is obtained. As a polyamide-based coating layer, for example, a polyamide-based separation functional layer obtained by interfacial polymerization of a polyfunctional amine component and a polyfunctional acid halide component on a porous support membrane is well known. Such a polyamide-based separation functional layer is known to have a pleated microstructure, and the thickness of this layer is not particularly limited, but is about 0.05 to 2 μm, preferably 0.1 to 1 μm. It is known that if this layer is too thin, film surface defects are likely to occur, and if it is too thick, the transmission performance deteriorates.

  The method for forming the polyamide-based separation functional layer on the surface of the polymer porous layer is not particularly limited, and any known method can be used. Examples of the method include an interfacial polymerization method, a phase separation method, and a thin film coating method. In the present invention, the interfacial polymerization method is particularly preferably used. In the interfacial polymerization method, for example, the polymer porous layer is coated with a polyfunctional amine component-containing amine aqueous solution, and then an organic solution containing a polyfunctional acid halide component is brought into contact with the amine aqueous solution-coated surface to cause interfacial polymerization. This is a method for forming a skin layer. In this method, it is preferable to proceed by removing the surplus as appropriate after the application of the aqueous amine solution and the organic solution. In this case, as a removal method, a method of inclining a target film, a method of blowing off a gas, a rubber, For example, a method of scraping off a blade by contacting the blade is preferably used.

  In the above step, the time until the aqueous amine solution and the organic solution come into contact depends on the composition of the aqueous amine solution, the viscosity, and the pore diameter of the surface of the porous support membrane, but is about 1 to 120 seconds, preferably Is about 2 to 40 seconds. If the interval is too long, the aqueous amine solution may permeate and diffuse deep inside the porous support membrane, and a large amount of unreacted polyfunctional amine component may remain in the porous support membrane, resulting in problems. . When the application interval of the solution is too short, an excessive amine aqueous solution remains, so that the film performance tends to be lowered.

  After the contact between the aqueous amine solution and the organic solution, the skin layer is preferably formed by heating and drying at a temperature of 70 ° C. or higher. Thereby, the mechanical strength and heat resistance of the film can be increased. The heating temperature is more preferably 70 to 200 ° C, particularly preferably 80 to 130 ° C. The heating time is preferably about 30 seconds to 10 minutes, more preferably about 40 seconds to 7 minutes.

  The polyfunctional amine component contained in the amine aqueous solution is a polyfunctional amine having two or more reactive amino groups, and examples thereof include aromatic, aliphatic, and alicyclic polyfunctional amines. Examples of the aromatic polyfunctional amine include m-phenylenediamine, p-phenylenediamine, o-phenylenediamine, 1,3,5-triaminobenzene, 1,2,4-triaminobenzene, 3,5- Examples include diaminobenzoic acid, 2,4-diaminotoluene, 2,6-diaminotoluene, N, N′-dimethyl-m-phenylenediamine, 2,4-diaminoanisole, amidol, xylylenediamine and the like. Examples of the aliphatic polyfunctional amine include ethylenediamine, propylenediamine, tris (2-aminoethyl) amine, and n-phenyl-ethylenediamine. Examples of the alicyclic polyfunctional amine include 1,3-diaminocyclohexane, 1,2-diaminocyclohexane, 1,4-diaminocyclohexane, piperazine, 2,5-dimethylpiperazine, 4-aminomethylpiperazine, and the like. It is done. These polyfunctional amines may be used alone or in combination of two or more. In particular, in the present invention, it is preferable to use m-phenylenediamine as a main component, from which a highly dense separation function layer can be obtained.

  The polyfunctional acid halide component contained in the organic solution is a polyfunctional acid halide having two or more reactive carbonyl groups, and examples thereof include aromatic, aliphatic, and alicyclic polyfunctional acid halides. Examples of the aromatic polyfunctional acid halide include trimesic acid trichloride, terephthalic acid dichloride, isophthalic acid dichloride, biphenyldicarboxylic acid dichloride, naphthalene dicarboxylic acid dichloride, benzenetrisulfonic acid trichloride, benzenedisulfonic acid dichloride, and chlorosulfonylbenzene. And dicarboxylic acid dichloride. Examples of the aliphatic polyfunctional acid halide include propanedicarboxylic acid dichloride, butanedicarboxylic acid dichloride, pentanedicarboxylic acid dichloride, propanetricarboxylic acid trichloride, butanetricarboxylic acid trichloride, pentanetricarboxylic acid trichloride, glutaryl halide, azide. Poil halide etc. are mentioned. Examples of the alicyclic polyfunctional acid halide include cyclopropane tricarboxylic acid trichloride, cyclobutane tetracarboxylic acid tetrachloride, cyclopentane tricarboxylic acid trichloride, cyclopentane tetracarboxylic acid tetrachloride, cyclohexane tricarboxylic acid trichloride, and tetrahydro Examples include furantetracarboxylic acid tetrachloride, cyclopentanedicarboxylic acid dichloride, cyclobutanedicarboxylic acid dichloride, cyclohexanedicarboxylic acid dichloride, and tetrahydrofurandicarboxylic acid dichloride. These polyfunctional acid halides may be used alone or in combination of two or more. Among them, it is preferable to use an aromatic polyfunctional acid halide that provides a dense separation functional layer. Moreover, it is preferable to form a crosslinked structure using a trifunctional or higher polyfunctional acid halide as at least a part of the polyfunctional acid halide component.

  In the interfacial polymerization method, the concentration of the polyfunctional amine component in the aqueous amine solution is not particularly limited, but is preferably 0.1 to 7% by weight, and more preferably 1 to 5% by weight. If the concentration of the polyfunctional amine component is too low, defects are likely to occur in the skin layer, and the salt blocking performance tends to be reduced. On the other hand, when the concentration of the polyfunctional amine component is too high, it becomes too thick and the permeation flux tends to decrease.

  The concentration of the polyfunctional acid halide component in the organic solution is not particularly limited, but is preferably 0.01 to 5% by weight, and more preferably 0.05 to 3% by weight. If the concentration of the polyfunctional acid halide component is too low, the unreacted polyfunctional amine component is increased, and defects are likely to occur in the skin layer. On the other hand, if the concentration of the polyfunctional acid halide component is too high, the amount of unreacted polyfunctional acid halide component increases, so that the skin layer becomes too thick and the permeation flux tends to decrease.

  The organic solvent containing the polyfunctional acid halide is not particularly limited as long as it has low solubility in water and does not deteriorate the porous support membrane, and can dissolve the polyfunctional acid halide component. For example, cyclohexane, Examples thereof include saturated hydrocarbons such as heptane, octane and nonane, and halogen-substituted hydrocarbons such as 1,1,2-trichlorotrifluoroethane. Preferred is a saturated hydrocarbon having a boiling point of 300 ° C. or lower, more preferably a boiling point of 200 ° C. or lower.

You may add the additive for the purpose of the improvement of various performance and a handleability to the said amine aqueous solution and organic solution. Examples of the additive include polymers such as polyvinyl alcohol, polyvinyl pyrrolidone and polyacrylic acid, polyhydric alcohols such as sorbitol and glycerin, and surfactants such as sodium dodecylbenzenesulfonate, sodium dodecylsulfate, and sodium laurylsulfate. A basic compound such as sodium hydroxide, trisodium phosphate, and triethylamine that removes hydrogen halide produced by polymerization, an acylation catalyst, and a solubility parameter described in JP-A-8-224452 is 8 to 14 (cal / Cm ³ ) ^1/2 compound and the like.

  A coating layer composed of various polymer components may be further provided on the exposed surface of the polyamide-based separation functional layer. The polymer component is not particularly limited as long as it does not dissolve the separation functional layer and the porous support membrane and does not elute during the water treatment operation. For example, polyvinyl alcohol, polyvinyl pyrrolidone, hydroxypropyl cellulose, polyethylene Examples thereof include glycols and saponified polyethylene-vinyl acetate copolymers. Among these, it is preferable to use polyvinyl alcohol, in particular, by using polyvinyl alcohol having a saponification degree of 99% or more, or by crosslinking polyvinyl alcohol having a saponification degree of 90% or more with the polyamide-based resin of the skin layer, It is preferable to use a structure that does not easily dissolve during water treatment.

  In the present invention, at least one surface of the separation membrane of the hydrophilic polymer or the separation membrane after the hydrophilization treatment has a porous structure or non-porous structure having an average pore diameter of 1,000 nm or less, and is concentrated by increasing the permeation flow rate. From the viewpoint of improving the processing efficiency, a porous structure having an average pore diameter of 1 to 500 nm is preferable.

(Membrane element)
The membrane element of the present invention includes the separation membrane for concentrating bubble liquid as described above. The form of such a membrane element is not particularly limited, and examples thereof include a flat membrane type such as a frame and plate type, a spiral type, and a pleated type. Moreover, when the separation membrane for concentrating bubble liquid is a hollow fiber membrane, a hollow fiber membrane element in which a plurality of hollow fiber membranes are bundled and one or both ends are sealed with a resin or the like is used. Of these membrane elements, spiral membrane elements are generally preferred from the relationship between pressure and flow efficiency.

  For example, as shown in FIG. 2, the spiral membrane element includes a laminated body including a separation membrane 2, a supply-side flow path member 6, and a permeate-side flow path member 3, and a perforated central tube around which the laminated body is wound. 5 and a sealing portion 21 that prevents mixing of the supply-side flow path and the permeation-side flow path. In the present embodiment, an example in which a plurality of separation membrane units including the separation membrane 2, the supply-side flow path material 6 and the permeation-side flow path material 3 are wound bodies R wound around the central tube 5. Indicates.

  The sealing part 21 for preventing the mixing of the supply side flow path and the permeation side flow path is, for example, an envelope shape by overlapping the separation membrane 2 on both surfaces of the permeation side flow path material 3 and bonding the three sides. When the film 4 (bag-like film) is formed, the sealing portion 21 is formed on the sealing portion 21 on the outer peripheral side edge, the upstream side edge, and the downstream side edge. Moreover, it is preferable to provide the sealing part 21 also between the inner peripheral side edge part of the upstream side edge and the downstream side edge and the central tube 5.

  The envelope film 4 is attached to the central tube 5 at its opening, and is wound spirally around the outer peripheral surface of the central tube 5 together with the net-like (net-like) supply-side flow path member 6 so that the wound body R becomes It is formed. An upstream end member 10 such as a seal carrier is provided on the upstream side of the wound body R, and a downstream end member 20 such as a telescope prevention member is provided on the downstream side as necessary.

  In such a spiral membrane element, the envelope membrane 4 can normally wind 20 to 40 sets of envelope membranes 4.

  When the membrane element 1 is used, the supply liquid 7 is supplied from one end face side of the membrane element 1. The supplied supply liquid 7 flows along the supply-side flow path material 6 in a direction parallel to the axial direction A1 of the central tube 5 and is discharged as a concentrated liquid 9 from the other end face side of the membrane element 1. Further, the permeated liquid 8 that has permeated the separation membrane 2 in the course of the supply liquid 7 flowing along the supply-side flow path material 6 passes through the aperture 5a along the permeation-side flow path material 3 as shown by the broken line arrows in the figure. It flows into the center tube 5 and is discharged from the end of the center tube 5.

  The channel material generally has a role of ensuring a gap for uniformly supplying fluid to the membrane surface. As such a channel material, for example, a net, a knitted fabric, a concavo-convex processed sheet or the like can be used, and a material having a maximum thickness of about 0.1 to 3 mm can be appropriately used as necessary. In such a channel material, it is preferable that the pressure loss is low, and further, a material that causes an appropriate turbulent flow effect is preferable. In addition, the channel material is installed on both sides of the separation membrane, but it is common to use different channel materials as the supply side channel material on the supply liquid side and the permeate side channel material on the permeate side. . The supply-side channel material uses a coarse and thick net-like channel material, while the permeate-side channel material uses a fine woven or knitted channel material.

  The supply-side channel material is provided on the inner surface side of the bifurcated separation membrane, for example. As the structure of the supply-side channel material, a network structure in which linear objects are generally arranged in a lattice can be preferably used. Although it does not specifically limit as a material to comprise, Polyethylene, a polypropylene, etc. are used. The thickness of the supply side channel material is generally 0.2 to 2.0 mm, preferably 0.5 to 1.0 mm.

  The permeate-side channel material is provided on the outer surface side of the bifurcated separation membrane, for example. This permeation side channel material is required to support the pressure applied to the membrane from the back side of the membrane and secure a permeate channel. In general, a net or tricot knitted fabric made of polyethylene or polypropylene is used. In particular, a tricot knitted fabric made of polyethylene terephthalate is particularly preferably used.

  The central tube is not particularly limited as long as it is a perforated hollow tube having a plurality of small holes on the wall surface of the pipe (hollow tube). At the time of bubbling liquid concentration, the permeated liquid that has passed through the separation membrane enters the hollow tube through the hole in the wall surface, and forms a permeate side flow path. The length of the central tube is generally longer than the length of the element in the axial direction, but a central tube having a connection structure such as a plurality of divisions may be used. Although it does not specifically limit as a material which comprises a center pipe | tube, A thermosetting resin or a thermoplastic resin is used.

(Membrane module)
The membrane module of the present invention includes a membrane element including the separation membrane for concentrating bubble liquid as described above, and a container that accommodates the membrane element and forms a concentration side channel and a permeation side channel. Features.

  The membrane module 30 shown in the present embodiment includes, for example, a spiral membrane element 1, a supply unit 32 that supplies the supply element 7, and a concentration unit 9 that discharges the concentrate 9, as shown in FIG. 3. A container 31 having a liquid discharge part 33 and a permeate discharge part 34 for discharging the permeate 8.

  In the illustrated example, the upstream end member 10 holds the sealing material 11, and the sealing material 11 is in pressure contact with the inner wall of the container 31, thereby leading the supply liquid 7 to the inside of the wound body R of the membrane element 1. It has become. The concentrated liquid 9 that has flowed out from the inside of the wound body R flows with the concentrated liquid discharger 33 through the internal space of the container 31. Further, one end (the left end in FIG. 3) of the central tube 5 is closed, and the other end (the right end in FIG. 3) is connected to the permeate discharge part 34 of the container 31. When a plurality of membrane elements 1 are accommodated in the container 31, the central tubes 5 of the adjacent membrane elements 1 are connected to each other via a connecting member (not shown) or the like. With such a structure, the container 31 forms a concentration side channel and a permeation side channel.

  In the present invention, a liquid containing bubbles having a diameter of less than 1 μm is supplied from the supply unit 32 as the supply liquid 7 in a state where the concentration side flow path is pressurized, so that the bubble liquid is separated from the bubble liquid concentration separation membrane. The concentrated concentrate 9 can be discharged from the concentrated liquid discharge portion 33. Further, the permeated liquid 8 that has permeated through the bubble liquid concentrating separation membrane can be discharged from the permeated liquid discharging section 34.

  To bring the concentration side flow path into a pressurized state, for example, as shown in FIG. 5, when the supply liquid 7 is pressurized and supplied from the supply liquid tank 35 to the container 31 by the pump 37, The pressure in the concentration side flow path can be adjusted by adjusting the flow rate by the valve 39 while circulating the concentrated liquid 9 through the pipe 41 via the valve 39 while circulating the part through the pipe 42. At that time, the pressure and flow rate can be measured by the pressure gauge 38 and the flow meter 40, respectively. The permeate 8 is discharged to the permeate tank 43.

  The pipe 42 is preferably provided with a valve for adjusting the flow rate in order to facilitate pressure adjustment.

  When the bubble liquid is concentrated by the membrane module of the present invention, the pressure of the concentration side flow path is determined according to the permeation flux of the separation membrane, and may be 0.05 to 6 MPa, for example. In addition, the average linear velocity of the supply liquid on the film surface is preferably 0.1 to 100 cm / second, and more preferably 1 to 50 cm / second, from the viewpoint of suppressing the disappearance of bubbles. More preferably, it is 5-30 cm / sec. If the average linear velocity of the supply liquid is too low, the effect of suppressing the disappearance of bubbles is insufficient, and if it is too high, the pressure loss of the flow path increases and energy consumption increases, which is not preferable.

(Other embodiments)
(1) In the above-described embodiment, an example of a spiral membrane element having a flat membrane has been shown. However, in the present invention, a membrane element having a hollow fiber membrane or a membrane module using the membrane element can be configured. is there.

  For example, as shown in FIG. 4, a plurality of hollow fiber membranes that are separation membranes 2 are bundled and sealed so that one end (the left end in FIG. 4) is closed with a closing member 15 such as resin, A hollow fiber membrane element whose end (right end in FIG. 4) is sealed with a sealing member 16 such as resin can be used. A sealing material 17 is interposed between the outer periphery of the sealing member 16 and the inner surface of the container 31. As a result, a concentration side flow path is formed, and the supply liquid 7 is supplied from the supply part 32, whereby the concentrate 9 in which the bubble liquid is concentrated by the separation liquid for bubble liquid concentration is discharged from the concentrate discharge part 33. Can do. Further, the permeated liquid 8 that has permeated through the bubble liquid concentrating separation membrane can be discharged from the permeated liquid discharging section 34.

  In the illustrated example, one end (left end in FIG. 4) is sealed so as to be closed with a closing member 15 such as a resin, but a plurality of hollow fiber membranes are arranged in a U-shape, It is also possible to provide a hollow fiber membrane element whose end is sealed so as to be opened by a sealing member 16 such as a resin.

  Further, it is possible to provide a hollow fiber membrane element in which the end portions on both sides of the hollow fiber membrane are sealed so as to be opened with a sealing member 16 such as a resin. The concentration side flow path and the permeation side flow path can be formed in the container 31 by interposing the sealing material 17 on the inner surface of the container 31. In the membrane module having such a structure, it is possible to supply a liquid for concentrating bubble liquid not only to the outside of the hollow fiber membrane but also to the inside thereof.

  (2) In the above-described embodiment, the example in which the membrane module is used in the method of concentrating the bubble liquid while circulating the liquid is shown. However, the membrane module of the present invention is a method of concentrating the bubble liquid in one pass. May be used for

  For example, as shown in FIG. 6, when supplying the supply liquid 7 from the supply liquid tank 35 to the container 31 with the pump 37, the concentrated liquid 9 is discharged by the pipe 41 through the valve 39, By adjusting the flow rate, the pressure in the concentration side channel can be adjusted. Thereby, the permeate 8 can be discharged while concentrating the bubble liquid.

  (3) In the above-described embodiment, the supply liquid having bubbles is stored in the supply liquid tank and then supplied to the membrane module. However, directly from the apparatus for producing the liquid having bubbles having a diameter of less than 1 μm, It is also possible to supply liquid to the membrane module.

  EXAMPLES Hereinafter, although an Example and a comparative example are given and this invention is demonstrated in detail, this invention is not limited to these Examples.

(Example of production of separation membrane)
A mixture of 18.3% by weight of polysulfone (manufactured by Solvay Advanced Polymers, P-3500) and 81.7% by weight of dimethylformamide on a nonwoven fabric made of polyester (Awa Paper Co., Ltd., 70 g / m ² , thickness 90 μm). The liquid was applied. Thereafter, the polyester nonwoven fabric coated with the mixed solution was immersed in pure water at 20 ° C., and further immersed in pure water at 45 ° C. Thus, a polysulfone porous membrane having a thickness of about 130 μm was obtained.

  The separation membrane here is an asymmetric membrane having different average pore sizes on both sides of the membrane, and the average pore size on the surface with the smaller pore size was 20 nm. The average pore diameter was measured by reading from the surface observation of SEM (hereinafter the same).

<Example 1>
The polysulfone porous membrane obtained in the preparation example of the separation membrane was taken out after being immersed in an aqueous methacrylic acid solution (concentration 80 wt%), accelerated voltage 250 kV, irradiation dose 30 kGy, under nitrogen atmosphere (oxygen concentration 300 ppm or less), Electron beam irradiation was performed at room temperature, and methacrylic acid was graft-polymerized on the base material. Next, in order to remove the substrate and unreacted methacrylic acid monomer and polymer, immersion washing was performed for 2 hours in warm water at 60 ° C., followed by drying for 2 hours in a dryer at 40 ° C. Separation membrane (shown as “graft membrane” in Table 1 below) was obtained. The average pore diameter of the surface of the separation membrane having the smaller pore diameter was 20 nm.

<Example 2>
An aqueous solution (A) was prepared by mixing 3.0 g of m-phenylenediamine, 0.15 g of sodium lauryl sulfate, 6.0 g of benzenesulfonic acid, 3.0 g of triethylamine, and 87.85 g of water. The aqueous solution (A) was applied on the polysulfone porous membrane obtained in the production example of the separation membrane, and the excess amine aqueous solution was removed. Next, an isooctane solution containing 0.2% by weight of trimesic acid chloride was further applied. After that, the excess isooctane solution is removed and held in a dryer at 100 ° C. for 2 minutes to form a polyamide skin layer (thickness: about 200 nm, non-porous structure) on the separation membrane. A separation membrane for bubbling liquid concentration of Example 2 (shown as “coating membrane” in Table 1 described later) was obtained.

<Comparative Example 1>
The porous membrane made of polysulfone obtained in the production example of the separation membrane was used as a separation membrane for concentrating bubble liquid (shown as “polysulfone membrane” in Table 1 described later) without surface treatment.

(Measurement of bubble contact angle in water)
The produced separation membranes for concentrating bubble liquids of Examples 1 and 2 and Comparative Example 1 were immersed in pure water at 25 ° C. for 10 minutes, and then an automatic contact angle measuring device (trade name “DM-300 manufactured by Kyowa Interface Science Co., Ltd.” )) Was used to measure the contact angle of air (bubbles) adhering to the separation membrane for bubbling liquid concentration. The measurement was performed with N = 5 times for a bubble having a diameter of 400 to 500 μm. At this time, measurement was performed while supplying air bubbles with a syringe needle.
(Measurement of UFB number density before and after concentration)
The bubble liquid was concentrated using the bubble liquid concentration shown in FIG. 5, and the number density of the ultra fine bubbles was measured.

  That is, the produced flat membrane-like separation membranes for Examples 1 and 2 and Comparative Example 1 were cut into a predetermined shape and size, and a flat membrane evaluation cell (C10-T, manufactured by Nitto Denko Corporation) was cut. ). Next, 4L of ultra fine bubble water (mode diameter of bubbles is 0.1 μm, number density is 100 million / mL) manufactured with an ultra fine bubble generator (made by IDEC, FZ1N-02 type) The tank was prepared, and ultrafine bubble raw water was supplied at a pressure of 0.5 MPa and a flow rate of 1 L / min to the side having a small pore diameter (separation surface side) of the separation membrane for bubbling liquid concentration. By this operation, filtration was performed while circulating the ultrafine bubble raw water until the raw water tank reached 0.4 L to obtain a 10-fold concentrated liquid.

  The number density of the ultra fine bubbles contained in the ultra fine bubble raw water and the 10-fold concentrated liquid was respectively measured with a nanoparticle analyzer (Nanosite, NS500), and the increase rate of the number density of the ultra fine bubbles was calculated.

  Table 1 shows the measurement results of the above measurements of the bubble liquid concentrating separation membranes according to Examples 1 and 2 and Comparative Example 1.

  As shown in the results of Table 1, when a separation membrane having a bubble contact angle in water of 140 ° or more was used by surface treatment as in Examples 1 and 2, the membrane and It is possible to obtain a high-concentration bubble-containing liquid by suppressing the disappearance of bubbles due to contact. On the other hand, when a polysulfone separation membrane that is widely used as a separation membrane is used, even if the stock solution is concentrated 10 times, most of the bubbles disappear, thereby obtaining a high-concentration bubble-containing liquid. I could not.

<Example 3>
In Example 1, using the polysulfone porous membrane (ungrafted product) obtained in the separation membrane preparation example, surface treatment (coating) with polyvinyl alcohol (Kuraray Co., Ltd., product name KM-118). Except for the above, a separation membrane for concentrating bubble liquid (bubble contact angle 155 °) was prepared in the same manner as in Example 1, and the UFB number density before and after concentration was measured. As a result, the rate of increase in UFB number density upon 10-fold concentration was 3.7 times. The coating with polyvinyl alcohol was performed as follows.

The polysulfone porous membrane (ungrafted product) obtained in the preparation example of the separation membrane was dipped in a 10% by weight isopropyl alcohol aqueous solution to be in a wet state, and then 0.05% by weight polyvinyl alcohol on the polysulfone membrane side. The aqueous solution was applied and dried in an oven at 80 ° C.
<Comparative Examples 2-4>
Hydrophobic polyethersulfone separation membrane (average pore size 10 nm, contact angle 75 °), polyvinylidene fluoride separation membrane (average pore size 500 nm, contact angle 56 °), epoxy resin separation membrane (average pore size 50 nm, contact angle 110) Were used as a separation membrane for bubbling liquid concentration without any surface treatment.

  As a result of measuring the UFB number density before and after the concentration, the increase rate of the UFB number density at the time of 10 times to 50 times concentration was less than twice.

DESCRIPTION OF SYMBOLS 1 Membrane element 2 Separation membrane 3 Permeate side channel material 4 Envelope-shaped membrane 5 Center tube 6 Supply side channel material 7 Supply liquid 8 Permeate 9 Concentrate 30 Membrane module 31 Container

Claims (7)

  A separation membrane for concentrating bubble liquid, wherein the bubble contact angle in water is 140 ° or more on at least one surface.   The separation membrane for concentrating bubble liquid according to claim 1, which is used when concentrating a bubble liquid having a diameter of less than 1 µm present in the liquid.   The separation membrane for concentrating bubble liquid according to claim 1 or 2, wherein the one surface has a porous structure having an average pore diameter of 1,000 nm or less or a non-porous structure.   The separation membrane for concentrating bubble liquid according to any one of claims 1 to 3, further comprising a hydrophilic polymer porous layer or a non-porous layer on the one surface.   The separation membrane for concentrating bubble liquid according to claim 4, wherein the polymer porous layer or the non-porous layer is subjected to a hydrophilic treatment by coating with a hydrophilic substance or grafting with a hydrophilic polymer.   A membrane element comprising the separation membrane for concentrating bubble liquid according to any one of claims 1 to 5. A membrane module comprising: the membrane element according to claim 6; and a container that accommodates the membrane element and forms a concentration side channel and a permeation side channel.