Method for regenerating semipermeable membrane

Abstract

Provided is a method for regenerating a semipermeable membrane that has a history of contacting a liquid body containing an organic solvent. The method for regenerating a semipermeable membrane comprises bringing the membrane into contact with a regeneration agent. The regeneration agent is selected from liquids at 50°C or higher that contain water and gases at 80°C or higher that contain water.

Description

Method for regenerating semipermeable membranes

[0001] The present invention relates to a method for regenerating a semipermeable membrane.

[0002] Membrane separation is widely used in many technical fields. For example, forward osmosis membranes, reverse osmosis membranes, nanofiltration membranes, ultrafiltration membranes, microfiltration membranes, etc. are used for purposes such as wastewater treatment, seawater desalination, concentration of intermediate compounds, and purification of target substances.

[0003] In membrane separation using these semipermeable membranes, the amount of raw liquid permeated through the semipermeable membrane and the separation performance may decrease over a long period of operation. Therefore, in order to obtain the desired throughput and separation performance in membrane separation, it is necessary not only to improve the initial performance of the membrane used but also to restore the membrane performance that has decreased during operation and regenerate the membrane.

[0004] In this regard, several techniques for regenerating membrane separation membranes have been proposed in the prior art. For example, Patent Documents 1 to 3 disclose a technique in which, while a stock solution is flowing through the stock solution side of a forward osmosis membrane module, the flowing liquid on the draw solution side is switched from the draw solution to a cleaning liquid having a lower osmotic pressure than the stock solution, and the forward osmosis membrane is backwashed by utilizing the osmotic pressure difference between the cleaning liquid and the stock solution. Patent Document 4 also discloses a technique for cleaning reverse osmosis membranes and nanofiltration membranes with an iodine compound. Furthermore, Patent Document 5 discloses a technique for regenerating a reverse osmosis membrane for producing ultrapure water by flowing hot water through the membrane.

[0005] International Publication No. 2021 / 187438 Japanese Patent Application Laid-Open No. 2021-003663 Japanese Patent Application Laid-Open No. 2012-250200 Japanese Patent Application Laid-Open No. 2011-161435 Japanese Patent Application Laid-Open No. 2018-058018

[0006] The techniques described in the above Patent Documents 1 to 5 relate to means for recovering performance degradation caused by semipermeable membrane fouling, scale formation on the semipermeable membrane, and the like, which are due to solutes and insolubles contained in the feed solution during membrane separation of a feed solution containing water as a solvent. In contrast, the present inventors have found that degradation in semipermeable membrane performance is also observed when membrane separation of a feed solution containing an organic solvent is continued for a long period of time. The present inventors have further found that this performance degradation cannot be recovered by conventionally known methods for regenerating semipermeable membranes.

[0007] The present invention has been made in view of the above circumstances. An object of the present invention is to provide a method for regenerating a semipermeable membrane whose performance has deteriorated due to continued operation in membrane separation of a feed solution containing an organic solvent as a solvent. A method for regenerating a semipermeable membrane whose performance has deteriorated due to continued operation in membrane separation of a feed solution containing an organic solvent as a solvent has not been known to date.

[0008] The present invention is as follows.

[0009] <Aspect 1> A method for regenerating a semipermeable membrane, wherein the semipermeable membrane has a history of contact with a liquid containing an organic solvent, the regeneration method comprising contacting the semipermeable membrane with a regenerating agent, wherein the regenerating agent is selected from a water-containing liquid at 50°C or higher and a water-containing gas at 80°C or higher. <Aspect 2> The method for regenerating a semipermeable membrane according to Aspect 1, wherein the semipermeable membrane has a support membrane and a separation functional layer. <Aspect 3> The method for regenerating a semipermeable membrane according to Aspect 2, wherein the separation functional layer comprises polyamide. <Aspect 4> The method for regenerating a semipermeable membrane according to Aspect 1 or 2, wherein the semipermeable membrane is a forward osmosis membrane. <Aspect 5> The method for regenerating a semipermeable membrane according to Aspect 1 or 2, wherein the regenerating agent is water vapor at 100°C or higher and 140°C or lower. <Aspect 6> The method for regenerating a forward osmosis membrane according to Aspect 4, wherein the regenerating agent is water vapor at 100°C or higher and 140°C or lower. Aspect 7: The method for regenerating a semipermeable membrane according to Aspect 1 or 2, wherein the regenerant is water at 70°C or higher and 100°C or lower. Aspect 8: The method for regenerating a forward osmosis membrane according to Aspect 4, wherein the regenerant is water at 70°C or higher and 100°C or lower. Aspect 9: The method for regenerating a semipermeable membrane according to Aspect 1, wherein the contact time between the semipermeable membrane and the regenerant is 2 minutes or higher and 10 hours or lower. Aspect 10: The method for regenerating a semipermeable membrane according to Aspect 5, wherein the contact time between the semipermeable membrane and the regenerant is 2 minutes or higher and 10 hours or lower. Aspect 11: The method for regenerating a semipermeable membrane according to Aspect 6, wherein the contact time between the semipermeable membrane and the regenerant is 2 minutes or higher and 10 hours or lower. Aspect 12: The method for regenerating a semipermeable membrane according to Aspect 1 or 2, wherein the organic solvent contained in the liquid is a hydrophilic organic solvent. Aspect 13: The method for regenerating a semipermeable membrane according to Aspect 12, wherein the liquid material is an aqueous solution containing the hydrophilic organic solvent, and the concentration of the hydrophilic organic solvent in the liquid material is 20% by mass or more based on the total mass of the liquid material. Aspect 14: The method for regenerating a semipermeable membrane according to Aspect 1 or 2, wherein the regeneration method comprises contacting the semipermeable membrane with water at a temperature below 50°C before contacting the semipermeable membrane with a regenerating agent. Aspect 15: The method for regenerating a semipermeable membrane according to Aspect 1 or 2, wherein the semipermeable membrane has a history of contact with a treating agent selected from a water-containing liquid at a temperature of 50°C or more and a water-containing gas at a temperature of 80°C or more before contacting the liquid material.<Aspect 16> The semipermeable membrane is a forward osmosis membrane, and when forward osmosis treatment is performed with water placed on one side of the forward osmosis membrane and a 3.5 mass % aqueous sodium chloride solution placed on the other side, the amount of salt back diffusion (R, unit: g / (m) ２ × hr) and water permeability (F, unit: kg / (m ２ The forward osmosis performance value (F / R) expressed as the ratio of the forward osmosis performance value (F × hr) to the forward osmosis performance value (F ０ / R ０ The method for regenerating a semipermeable membrane according to Aspect 1 or 2, wherein the semipermeable membrane is a forward osmosis membrane, and the amount of salt back diffusion (R, unit: g / (m)) when the forward osmosis membrane after regeneration is sandwiched between water and a 3.5 mass % aqueous sodium chloride solution and subjected to forward osmosis treatment is measured. ２ × hr) and water permeability (F, unit: kg / (m ２ The forward osmosis performance value (F / R) expressed as the ratio of the forward osmosis performance value (F × hr) to the forward osmosis performance value (F ０ / R ０ The method for regenerating a semipermeable membrane according to Aspect 1 or 2, wherein the regeneration efficiency is 0.85 times or more compared to that of a liquid containing an organic solvent. Aspect 18: A method for regenerating a semipermeable membrane, the regeneration method comprising: an organic solvent removal step of removing an organic solvent from a liquid containing an organic solvent through the semipermeable membrane; and a regeneration step of contacting the semipermeable membrane with a regenerating agent after the organic solvent removal step, the regenerating agent being selected from a water-containing liquid at 50°C or higher and a water-containing gas at 80°C or higher. Aspect 19: The method for regenerating a semipermeable membrane according to Aspect 18, wherein the semipermeable membrane has a support membrane and a separation functional layer. Aspect 20: The method for regenerating a semipermeable membrane according to Aspect 19, wherein the separation functional layer comprises polyamide. Aspect 21: The method for regenerating a semipermeable membrane according to Aspect 18 or 19, wherein the semipermeable membrane is a forward osmosis membrane. Aspect 22: The method for regenerating a semipermeable membrane according to any of Aspects 18 to 21, wherein the regenerating agent is water vapor at 100°C or higher and 140°C or lower.

[0010] According to the present invention, there is provided a method for regenerating a semipermeable membrane whose performance has deteriorated due to continued operation in membrane separation of a raw liquid containing an organic solvent as a solvent.

[0011] Hereinafter, an embodiment of the present invention (hereinafter simply referred to as "the present embodiment") will be described in detail, but the present invention is not limited to the present embodiment. The present invention can be modified in various ways without departing from the gist of the present invention.

[0012] In the method for regenerating a semipermeable membrane according to the first embodiment, the semipermeable membrane to be regenerated has a history of contact with a liquid containing an organic solvent, the method for regenerating a semipermeable membrane includes contacting the semipermeable membrane with a regenerating agent, and the regenerating agent is selected from a water-containing liquid at 50°C or higher and a water-containing gas at 80°C or higher.

[0013] In a second embodiment, there is provided a method for regenerating a semipermeable membrane, the method comprising: an organic solvent removal step of removing an organic solvent from a liquid containing an organic solvent through a semipermeable membrane; and a regeneration step of contacting the semipermeable membrane with a regenerant after the organic solvent removal step, wherein the regenerant is selected from a water-containing liquid at 50°C or higher and a water-containing gas at 80°C or higher.

[0014] The regeneration methods for semipermeable membranes according to the first and second embodiments described above may be interchangeable in terms of steps or components, or may combine steps or components according to both embodiments. Components and steps common to both embodiments, as well as components and steps preferred for both embodiments, will be described below.

[0015] The method for regenerating a semipermeable membrane may include a pre-washing treatment in which the semipermeable membrane is contacted with water at a temperature below 50° C. before contacting the semipermeable membrane with the regenerating agent.

[0016] The semipermeable membrane to which the semipermeable membrane regeneration method is applied is, for example, a semipermeable membrane whose performance has deteriorated due to continued operation in membrane separation of a raw solution containing an organic solvent. In such membrane separation, it is thought that the molecular structure of the semipermeable membrane "loosens" when the semipermeable membrane comes into contact with the organic solvent and interacts with it, causing the membrane performance to deteriorate. For example, it is thought that the organic solvent solvates in the separation functional layer of the semipermeable membrane, causing the separation functional layer to swell and resulting in a deterioration in membrane performance. Therefore, in this embodiment, a semipermeable membrane whose membrane performance has deteriorated due to contact with an organic solvent is contacted with a regenerant selected from a water-containing liquid at 50°C or higher and a water-containing gas at 80°C or higher. This removes the organic solvent from the semipermeable membrane and stabilizes the molecular structure of the semipermeable membrane, thereby regenerating the semipermeable membrane. However, the present invention is not bound by any particular theory.

[0017] Semipermeable membrane The semipermeable membrane to which the regeneration method according to the present embodiment is applied may be one whose molecular structure "relaxes" upon contact with an organic solvent. Therefore, the semipermeable membrane may include at least a portion composed of an organic material. Examples of organic materials constituting at least a portion of the semipermeable membrane in this embodiment include polyolefin, polysulfone, polyethersulfone, cellulose acetate, polyacrylonitrile, polyacrylic acid ester, polymethacrylic acid ester, polyester, polyamide, ceramic, and fluorine-based resin, and may be one or more selected from these.

[0018] The semipermeable membrane in this embodiment may be a semipermeable membrane having a support membrane and a separation functional layer. The separation functional layer does not have to be located directly above the support membrane, as long as it is on a surface of the semipermeable membrane that is exposed to water vapor, or it may be located directly above the support membrane. Furthermore, the semipermeable membrane may be composed of a support membrane and a separation functional layer, and the separation functional layer may be located on one or both sides of the support membrane, or there may be a single layer or multiple layers between the support membrane and the separation functional layer.

[0019] Examples of materials constituting the support membrane include polyethersulfone, polysulfone, polyketone, polyetheretherketone, polyphenylene ether, polyvinylidene fluoride, polyacrylonitrile, polyimine, polyimide, polybenzoxazole, polybenzimidazole, sulfonated tetrafluoroethylene, and polyamide, and it is preferable to use one or more materials selected from the group consisting of these.

[0020] The separation functional layer preferably contains polyamide, and more preferably consists of polyamide. A separation functional layer consisting of polyamide can be formed, for example, by performing interfacial polymerization of a polyfunctional acid halide and a polyfunctional aromatic amine on a support membrane, or by positioning the separation functional layer consisting of polyamide so that it becomes the surface of the semipermeable membrane.

[0021] The polyfunctional aromatic acid halide is an aromatic acid halide compound having two or more acid halide groups in one molecule. Specific examples include trimesic acid halide, trimellitic acid halide, isophthalic acid halide, terephthalic acid halide, pyromellitic acid halide, benzophenonetetracarboxylic acid halide, biphenyldicarboxylic acid halide, naphthalenedicarboxylic acid halide, pyridinedicarboxylic acid halide, and benzenedisulfonic acid halide. These can be used alone or in mixtures. Examples of halide ions in these aromatic acid halide compounds include chloride ions, bromide ions, and iodide ions. In this embodiment, trimesic acid chloride alone, a mixture of trimesic acid chloride and isophthalic acid chloride, or a mixture of trimesic acid chloride and terephthalic acid chloride is particularly preferred.

[0022] A polyfunctional aromatic amine is an aromatic amino compound having two or more amino groups per molecule. Specific examples include m-phenylenediamine, p-phenylenediamine, 3,3'-diaminodiphenylmethane, 4,4'-diaminodiphenylamine, 4,4'-diaminodiphenyl ether, 3,4'-diaminodiphenyl ether, 3,3'-diaminodiphenylamine, 3,5-diaminobenzoic acid, 4,4'-diaminodiphenyl sulfone, 3,3'-diaminodiphenyl sulfone, 3,4'-diaminodiphenyl sulfone, 1,3,5-triaminobenzene, and 1,5-diaminonaphthalene. These can be used alone or in mixtures. In this embodiment, one or more compounds selected from m-phenylenediamine and p-phenylenediamine are particularly preferred. The interfacial polymerization of a polyfunctional acid halide and a polyfunctional aromatic amine can be carried out according to a standard method.

[0023] The semipermeable membrane to which the regeneration method according to this embodiment is applied may have a history of contact with a treatment agent selected from a water-containing liquid at 50°C or higher and a water-containing gas at 80°C or higher before contacting the liquid containing an organic solvent. If the semipermeable membrane has a history of contact with such a treatment agent, the molecular structure is less likely to loosen when contacted with a liquid containing an organic solvent, thereby reducing the frequency with which the regeneration method according to this embodiment is performed. In particular, in the case of a semipermeable membrane having a support membrane and a separation functional layer on the support membrane, contact with the treatment agent has the advantage of strengthening the molecular structure of the separation functional layer. If the semipermeable membrane does not have a history of contact with the treatment agent, application of the regeneration method according to this embodiment may improve the membrane performance of the semipermeable membrane compared to its initial performance.

[0024] The semipermeable membrane to which the regeneration method according to this embodiment is applied may be, for example, a microfiltration membrane, an ultrafiltration membrane, a nanofiltration membrane, a reverse osmosis membrane, a forward osmosis membrane, or the like, and may in particular be a forward osmosis membrane. The semipermeable membrane may have any structure, for example, a hollow fiber membrane, a tubular membrane, or a flat membrane. In this embodiment, the semipermeable membrane may be in the form of a membrane module in which multiple semipermeable membranes are housed in a suitable housing.

[0025] <Liquid containing organic solvent> The semipermeable membrane to which the regeneration method according to the present embodiment is applied has a history of contact with a liquid containing an organic solvent. That is, the semipermeable membrane to which the regeneration method according to the present embodiment is applied is a semipermeable membrane that has been used for membrane separation of a raw liquid containing an organic solvent as at least a part of the solvent.

[0026] The organic solvent contained in the liquid may be one or more selected from, for example, aliphatic hydrocarbons, aromatic hydrocarbons, ketones, ethers, alcohols, carboxylic acids, aldehydes, nitrile compounds, amide compounds, halogenated hydrocarbons, sulfoxide compounds, ester compounds, and the like. Examples of aliphatic hydrocarbons include propane, butane, pentane, hexane, heptane, octane, decane, undecane, and cyclooctane; examples of aromatic hydrocarbons include benzene, toluene, xylene, biphenyl, pyridine, and pyrrole; examples of ketones include acetone, methyl ethyl ketone, diethyl ketone, methyl propyl ketone, methyl isobutyl ketone, methyl amyl ketone, cyclohexanone, acetophenone, and benzophenone; examples of ethers include dimethyl ether, ethyl methyl ether, diethyl ether, diphenyl ether, ethylene oxide, tetrahydrofuran, 1,4-dioxane, and anisole; examples of alcohols include methanol, ethanol, 1-propanol, 2-propanol, ethylene glycol, and glycerin; examples of carboxylic acids include acetic acid and trifluoroacetic acid; and examples of aldehydes include formaldehyde, acetaldehyde, propionaldehyde, and benzaldehyde. Examples of nitrile compounds include acetonitrile and propionitrile; examples of amide compounds include dimethylformamide; examples of halogenated hydrocarbons include chlorobenzene, dichloromethane, and 1,1,1-trichloroethane; examples of sulfoxide compounds include dimethyl sulfoxide; and examples of ester compounds include ethyl acetate.

[0027] The organic solvent contained in the liquid may be a hydrophilic organic solvent. The hydrophilic solvent may be, for example, one or more selected from alcohols having 1 to 3 carbon atoms and nitrile compounds, and may be one or more selected from methanol, ethanol, 1-propanol, 2-propanol, and acetonitrile. The liquid may also be an aqueous solution containing a hydrophilic organic solvent. In this case, the content of the hydrophilic organic solvent in the liquid may be 1% by mass or more, or may be 5%, 10%, 20%, 40%, or 50% by mass or more, relative to the total mass of the liquid. If the content of the hydrophilic organic solvent in the liquid is 5% by mass or more, the performance of the semipermeable membrane is likely to deteriorate, and therefore the effect of applying the regeneration method according to this embodiment can be more effectively achieved. The content of the hydrophilic organic solvent in the liquid may be less than 100% by mass, 95% by mass or less, 90% by mass or less, 85% by mass or less, or 80% by mass or less.

[0028] The semipermeable membrane to which the regeneration method according to the present embodiment is applied has its membrane performance deteriorated due to contact with a liquid containing an organic solvent. When the semipermeable membrane is a forward osmosis membrane, the degree of deterioration of the membrane performance can be expressed as the salt back-diffusion amount (R, unit: g / (m ２ × hr) and water permeability (F, unit: kg / (m ２ The forward osmosis performance can be estimated by the forward osmosis performance value (F / R) expressed as the ratio of the forward osmosis performance to the forward osmosis performance (F / R).

[0029] Specifically, when a forward osmosis membrane (semipermeable membrane) is sandwiched between two layers of water, one side of the membrane is covered with water and the other side is covered with a 3.5% by mass aqueous solution of sodium chloride, and forward osmosis treatment is performed, the amount of salt back diffusion (R, unit: g / (m ２ × hr) and water permeability (F, unit: kg / (m ２ The forward osmosis performance value (F / R) expressed as the ratio of the forward osmosis performance value (F × hr) to the forward osmosis performance value (initial forward osmosis performance value) when the semipermeable membrane has no history of contact with the liquid. ０ / R ０ When the forward osmosis performance value (F / R) is 0.90 times or less compared to the initial forward osmosis performance value (F ０ / R ０The benefits of the present invention can be more effectively enjoyed when the forward osmosis performance value (F / R) is 0.80 times or less, 0.70 times or less, 0.60 times or less, 0.50 times or less, 0.40 times or less, 0.30 times or less, or 0.25 times or less compared to the initial forward osmosis performance value (F ０ / R ０ ) may be 0.10 times or more, or 0.20 times or more.

[0030] <<Washing Pretreatment>> The regeneration method according to this embodiment comprises contacting a semipermeable membrane whose membrane performance has been reduced due to contact with a liquid containing an organic solvent with at least one regenerant selected from a water-containing liquid at 50°C or higher and a water-containing gas at 80°C or higher. Preferably, the semipermeable membrane whose membrane performance has been reduced is contacted with a regenerant selected from a water-containing liquid at 50°C or higher or a water-containing gas at 80°C or higher. However, in the regeneration method according to this embodiment, a washing pretreatment may be performed in which the semipermeable membrane is contacted with water at a temperature lower than 50°C before contacting the semipermeable membrane with the regenerant. In the regeneration method according to this embodiment, the washing pretreatment makes it possible to more easily remove the organic solvent from the semipermeable membrane.

[0031] The temperature of the water in the pre-washing treatment may be 45°C or less, 40°C or less, or 30°C or less, or 0°C or more, 10°C or more, or 15°C or more, and may typically be room temperature. The contact between the semipermeable membrane and water in the pre-washing treatment may be any of an immersion method in which the semipermeable membrane is immersed in water, a forward washing method in which water is passed from the raw solution side of the semipermeable membrane to the opposite side, and a backwashing method in which water is passed from the opposite side of the raw solution side to the raw solution side of the semipermeable membrane, or two or more of these may be performed sequentially. The time for the pre-washing treatment may be 10 minutes or more, 30 minutes or more, or 1 hour or more, and may be 24 hours or less, 12 hours or less, 8 hours or less, 6 hours or less, 4 hours or less, or 2 hours or less. When two or more of the immersion method, forward washing method, and backwashing method are performed, the above-mentioned pre-washing treatment time refers to the time for each of the immersion method, forward washing method, and backwashing method.

[0032] In the regeneration method according to this embodiment, before the semipermeable membrane is brought into contact with the regenerating agent, a drying treatment may be carried out by flowing dry air through the semipermeable membrane.

[0033] <<Regenerating Agent>> The regeneration method according to this embodiment comprises contacting a semipermeable membrane whose membrane performance has been reduced due to contact with a liquid containing an organic solvent with a regenerating agent selected from a water-containing liquid at 50° C. or higher and a water-containing gas at 80° C. or higher. Alternatively, the semipermeable membrane whose membrane performance has been reduced may be contacted with a regenerating agent selected from a water-containing liquid at 50° C. or higher or a water-containing gas at 80° C. or higher.

[0034] Since one of the purposes of the regeneration method of the present invention is to remove an organic solvent from a semipermeable membrane, the water-containing liquid used as a regenerant does not need to contain an organic solvent. However, this water-containing liquid may contain a solute. Examples of solutes include sodium chloride, magnesium chloride, and chlorine. Therefore, the water-containing liquid may be water or an aqueous solution containing the above-mentioned solute. Here, from the viewpoint of facilitating the removal of the solute used during regeneration after the membrane is regenerated by the present invention, the conductivity of the water-containing liquid may be 500 μS / cm or less, and preferably water having a purity equal to or higher than that of purified water specified in the Japanese Pharmacopoeia may be used.

[0035] The temperature of the liquid containing water as a regenerant is 50°C or higher, and may be 60°C or higher, 70°C or higher, 80°C or higher, 90°C or higher, 95°C or higher, or 100°C or higher, from the viewpoint of removing the organic solvent in the semipermeable membrane and effectively stabilizing the molecular structure of the semipermeable membrane. On the other hand, in consideration of the thermal efficiency when heating the liquid, the temperature of the liquid may be 140°C or lower, 130°C or lower, 120°C or lower, 110°C or lower, or 100°C or lower. The temperature of the liquid may be lower than the boiling point of the liquid. Note that the boiling point of the liquid may vary depending on the amount of solute contained in the liquid, the pressure, etc.

[0036] The contact between the semipermeable membrane and the water-containing liquid may be any of an immersion method in which the semipermeable membrane is immersed in the liquid, a forward washing method in which a liquid is passed through the semipermeable membrane from the source liquid side to the opposite side, and a backwashing method in which a liquid is passed through the semipermeable membrane from the side opposite the source liquid side to the source liquid side, or two or more of these may be performed sequentially. The contact time between the semipermeable membrane and the water-containing liquid may be 30 minutes or more, 45 minutes or more, 1 hour or more, or 2 hours or more, and may be 24 hours or less, 12 hours or less, 8 hours or less, 6 hours or less, or 4 hours or less. When two or more of the immersion method, forward washing method, and backwashing method are performed, the above contact time is the time for each of the immersion method, forward washing method, and backwashing method.

[0037] The type of gas containing water as a regenerating agent is not particularly limited, but is preferably water vapor from the viewpoint of ease of handling. The temperature of the gas containing water as a regenerating agent is 80°C or higher, 90°C or higher, 100°C or higher, more than 100°C, 110°C or higher, or 120°C or higher from the viewpoint of removing the organic solvent in the semipermeable membrane and effectively stabilizing the molecular structure of the semipermeable membrane, and may be 150°C or lower, 140°C or lower, 135°C or lower, 130°C or lower, or 125°C or lower from the viewpoint of thermal efficiency during heating. The gas containing water as a regenerating agent is preferably superheated steam having a temperature of more than 100°C from the viewpoint of semipermeable membrane regeneration efficiency.

[0038] The contact between the semipermeable membrane and the water-containing gas may be any of a static method in which the semipermeable membrane is placed in a sealed container, gas is supplied into the container, and the semipermeable membrane is allowed to stand; a forward washing method in which gas is passed from the raw liquid side of the semipermeable membrane to the opposite side; and a backwash method in which gas is passed from the opposite side of the raw liquid side to the raw liquid side of the semipermeable membrane, or two or more of these may be performed sequentially. The contact time between the semipermeable membrane and the water-containing gas may be 2 minutes or more, 5 minutes or more, 10 minutes or more, 20 minutes or more, 30 minutes or more, or 45 minutes or more, and may be 10 hours or less, 8 hours or less, 6 hours or less, 4 hours or less, or 2 hours or less. When two or more of the static method, forward washing method, and backwash method are performed, the above contact time is the time for each of the static method, forward washing method, and backwash method.

[0039] Effect of the Present Invention (Degree of Performance Recovery) A semipermeable membrane whose membrane performance has been reduced by contact with a liquid containing an organic solvent can have its membrane performance restored by applying the regeneration method of the present invention. According to the method of the present invention, when the semipermeable membrane is a forward osmosis membrane, the degree of recovery of membrane performance can be determined by multiplying the forward osmosis performance value (F / R) after recovery by the forward osmosis performance value (initial forward osmosis performance value) (F ０ / R ０ According to the regeneration method of the present invention, the forward osmosis performance value (F / R) after regeneration can be increased to 0.85 times or more compared to the initial forward osmosis performance value (F ０ / R ０ ) can be 0.90 times or more, 0.95 times or more, 0.98 times or more, or 0.99 times or more, and can also be 1.00 times.

[0040] Furthermore, as described above, when the semipermeable membrane has no history of contact with a treatment agent selected from a water-containing liquid at 50°C or higher and a water-containing gas at 80°C or higher before contacting with a liquid containing an organic solvent, the membrane performance of the semipermeable membrane may be improved compared to the initial performance by applying the regeneration method of the present invention. In this case, the forward osmosis performance value (F / R) after regeneration may be calculated as the initial forward osmosis performance value (F ０ / R ０ ) can be increased to about more than 1.00 times and not more than 1.20 times.

[0041] In the following examples and comparative examples, the water permeability (F) and salt back-diffusion rate (R) were measured, and the hollow fiber forward osmosis membrane module was brought into contact with a liquid containing an organic solvent as follows.

[0042] <<Measurement of Water Permeability (F) and Salt Back-Diffusion Amount (R) (Performance Evaluation)>> In the following Examples and Comparative Examples, the water permeability (F) and salt back-diffusion amount (R) were measured for the hollow fiber forward osmosis membrane module manufactured by the above-mentioned method, the module after contact with a liquid containing an organic solvent by the method described below, and the module after regeneration treatment by the method of each Example or Comparative Example. The water permeability (F) and salt back-diffusion amount (R) are respectively calculated using the following formulas (1) and (2): F = L / (M × H) (1) {In formula (1), L is the amount of water (kg) that has permeated the forward osmosis membrane, M is the effective surface area (m2) of the forward osmosis membrane, and H is the time (hr).} R = G / (M × H) (2) {In formula (1), G is the amount of salt (kg) that has permeated the forward osmosis membrane, and M is the effective surface area (m ２ ) and H is time (hr).

[0043] The forward osmosis performance value (F / R), which is the ratio of the salt back diffusion rate (R) to the water permeability rate (F), was calculated and used as an index of forward osmosis performance. It can be seen that the larger the forward osmosis performance value (F / R), the better the forward osmosis performance of the forward osmosis membrane module. In the following examples and comparative examples, we investigated how closely a module whose forward osmosis performance value (F / R) had decreased due to contact with an organic solvent could return to its initial forward osmosis performance value (F / R) through regeneration treatment.

[0044] The water permeability (F) and salt back-diffusion rate (R) of the module were measured under the following conditions. Purified water was used as the stock solution, and a 3.5% by mass sodium chloride aqueous solution was used as the draw solution. The stock solution was circulated through the space inside the hollow fibers of the forward osmosis membrane module (the separation function layer side), and the draw solution was circulated through the space outside, with the flow directions of the two solutions being parallel. The draw solution side was used as the pressure side, and the pressure was increased to 20 kPaG, and a forward osmosis treatment was performed for 20 minutes. During this treatment, the sodium chloride concentration in the draw solution was monitored, and a saturated aqueous solution of sodium chloride was added dropwise as appropriate to maintain a constant sodium chloride concentration in the draw solution. The temperatures of the stock solution and the draw solution were both 25°C, and the linear velocities of the stock solution and the draw solution on the surface of the hollow fiber membrane were both 3.0 cm / sec.

[0045] <<Contact between hollow fiber forward osmosis membrane module and liquid containing organic solvent>> As the liquid containing organic solvent, any of the following was used: 15% by mass acetonitrile aqueous solution (15% MeCN) 50% by mass acetonitrile aqueous solution (50% MeCN) Ethanol (EtOH) Toluene Ethyl acetate In the above, the acetonitrile used was a 99.5% pure product manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., the ethanol used was a 99.5% pure product manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., the toluene used was a 99.5% pure product manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., and the ethyl acetate used was a 99.5% pure product manufactured by Fujifilm Wako Pure Chemical Industries, Ltd. Purified water was used as the solvent (water) for the aqueous solution.

[0046] Both the inner and outer spaces of the hollow fibers in the forward osmosis membrane module were filled with a liquid containing an organic solvent, and the module was left to stand at 25°C for 168 hours for a contact treatment. Next, the module was held so that its axial direction was approximately vertical, and the liquid containing the organic solvent was drained by gravity through a liquid inlet / outlet at the bottom of the module. After that, water was circulated through both the inner and outer spaces of the hollow fibers in the forward osmosis membrane module to wash the forward osmosis membrane. The module after water washing was subjected to measurement of the water permeability (F) and salt back-diffusion rate R.

[0047] Example 1 The forward osmosis membrane housed in the hollow fiber forward osmosis membrane module in Example 1 was a forward osmosis membrane that used a hollow fiber membrane made of polysulfone (PSf) as a hollow fiber porous support membrane and had a polyamide separation functional layer on the inner surface of the hollow fiber membrane. The hollow fiber forward osmosis membrane module in Example 1 was produced as follows.

[0048] <Production of Hollow Fiber Porous Support Membrane> A homogeneous polymer solution (spinning dope) consisting of 19% by mass of polysulfone (Udel-P3500, manufactured by Solvay Specialty Polymers), 61% by mass of N-methyl-2-pyrrolidone (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.), and 20% by mass of tetraethylene glycol (manufactured by Tokyo Chemical Industry Co., Ltd.) was prepared as a spinning dope. The spinning dope was filled into a wet hollow fiber spinning machine equipped with a double spinneret. The spinning dope was discharged from the outer spinneret of the double spinneret, and the internal coagulation liquid (water) was discharged from the inner spinneret. The spinning dope was then introduced into a coagulation bath filled with water as the external coagulation liquid, and coagulation was carried out to obtain a hollow fiber porous support membrane. The obtained hollow fiber porous support membrane had an outer diameter of 1.00 mm, an inner diameter of 0.60 mm, and a membrane thickness of 0.20 mm.

[0049] <Production of Support Membrane Module> 130 of the hollow fiber porous support membranes cut to a length of 120 mm were housed in a cylindrical housing made of synthetic resin with a diameter of 20 mm, and both ends were fixed with an adhesive so as not to block the hollow portions of the hollow fibers. This resulted in a module with an effective length of 80 mm and an effective membrane inner surface area of ​​0.02 m. ２ A supported membrane module was manufactured. The internal space of this supported membrane module was divided into two by a membrane wall of a hollow fiber, and the two spaces were fluidically isolated except for the fact that liquid could pass through the membrane wall. The housing had a liquid inlet and outlet (liquid inlet and liquid outlet) that communicated with the space inside the hollow fiber, and a liquid inlet and outlet (liquid inlet and liquid outlet) that communicated with the space outside the hollow fiber.

[0050] <Production of a hollow fiber forward osmosis membrane module (formation of a separation functional layer)> An aqueous solution containing 1.9% by mass of m-phenylenediamine and 0.15% by mass of sodium lauryl sulfate (first solution) was passed through the space inside the hollow fibers of the support membrane module obtained above at a flow rate of 130 mL / min for 20 minutes. After completion of the liquid passage, the support membrane module was held so that the axial direction of the support membrane module was approximately vertical, and the first solution was drained by gravity through the liquid inlet / outlet at the bottom of the module. Next, with the inner surface of the hollow fibers wetted with the first solution, the space outside the hollow fibers of the support membrane module was reduced in pressure to 90 kPaG, and this reduced pressure state was maintained for 1 minute. Air was then circulated through the space inside the hollow fibers for 1 minute to remove excess first solution.

[0051] Subsequently, an n-hexane solution (second solution) containing 0.20% by mass of trimesoyl chloride (TMC) was passed through the space inside the hollow fibers of the support membrane module at a flow rate of 40 mL / min for 2 minutes to carry out interfacial polymerization and form a polyamide layer on the inner surface of the hollow fibers. Next, nitrogen was passed through the space inside the hollow fibers for 1 minute to remove excess second solution, and then water at 70°C was passed through the space inside the hollow fibers for 20 minutes to wash the inner surface of the hollow fibers.

[0052] Furthermore, with the two liquid inlets and outlets open, the module was placed in an autoclave (SX-500, manufactured by Tomy Seiko Co., Ltd.). Superheated steam at 121°C was circulated through the autoclave for 20 minutes to cure the polyamide layer. Subsequently, water was circulated through the space inside the hollow fibers of the module for 30 minutes to clean the surface of the polyamide layer after the moist heat treatment. Through the above operations, a separation function layer made of moist heat-treated polyamide was formed on the inner surface of the hollow fiber fibrous porous support membrane in the housing, thereby producing a hollow fiber forward osmosis membrane module.

[0053] <Evaluation of hollow fiber forward osmosis membrane module> First, the water permeation rate (F) and salt back diffusion rate (R) of an unused hollow fiber forward osmosis membrane module were measured by the method described above, and the forward osmosis performance value (F / R) (initial F / R) was calculated. Next, using a 15% by mass aqueous acetonitrile solution (MeCN 15%) as the liquid containing an organic solvent, the hollow fiber forward osmosis membrane module after initial F / R measurement was brought into contact with the liquid containing an organic solvent by the method described above, and then the water permeation rate (F) and salt back diffusion rate (R) were measured, and the forward osmosis performance value (F / R) (F / R after contact with organic solvent) was calculated.

[0054] Furthermore, the module after contact with the liquid containing an organic solvent was subjected to a regeneration treatment using superheated steam as a regenerant by the following method. The module after contact with the liquid containing an organic solvent was placed in an autoclave (SX-500, manufactured by Tomy Seiko Co., Ltd.) with the two liquid inlets and outlets open. Superheated steam at 121°C was circulated through the autoclave for 1 hour to perform a regeneration treatment. Thereafter, water at 25°C was circulated through the spaces inside and outside the hollow fibers of the module for 30 minutes to wash both surfaces of the hollow fibers after the regeneration treatment, completing the regeneration treatment. The water permeability (F) and salt back-diffusion rate (R) of the module after the regeneration treatment were measured using the method described above, and the forward osmosis performance value (F / R) (F / R after regeneration treatment) was calculated. The ratio of the F / R after regeneration treatment to the initial F / R value, expressed as a percentage, was evaluated as the "performance recovery rate." The evaluation results are shown in Table 1.

[0055] Example 2 Evaluation was carried out in the same manner as in Example 1, except that 50% MeCN was used as the liquid containing the organic solvent. The evaluation results are shown in Table 1.

[0056] Example 3 The forward osmosis membrane housed in the hollow fiber forward osmosis membrane module in Example 3 was a forward osmosis membrane that used a hollow fiber membrane made of polyketone (PK) as the hollow fiber porous support membrane and had a polyamide separation functional layer on the inner surface of the hollow fiber membrane. In Example 3, the hollow fiber forward osmosis membrane module was manufactured in the same manner as in the Examples, except that the hollow fiber porous support membrane made of polyketone (PK) and the support membrane module were each manufactured as follows.

[0057] <Production of hollow fiber porous support membrane> A polyketone (intrinsic viscosity 3.0 dL / g) completely alternatingly copolymerized with ethylene and carbon monoxide was added to a 63% by weight aqueous resorcinol solution at a polymer concentration of 17% by weight. The mixture was stirred at 80°C for 2 hours to dissolve the polymer and degas the polymer, preparing a transparent, uniform polymer solution (spinning solution). The spinning solution was charged into a wet hollow fiber spinning machine equipped with a double-nozzle at 50°C. The spinning solution was discharged from the outer spinning nozzle of the double-nozzle, and the internal coagulation liquid (water) was discharged from the inner spinning nozzle. The spinning solution was then introduced into a coagulation bath filled with a 40% by weight aqueous methanol solution as the external coagulation liquid, resulting in a hollow fiber porous support membrane. The resulting hollow fiber porous support membrane had an outer diameter of 0.60 mm, an inner diameter of 0.35 mm, and a membrane thickness of 0.125 mm.

[0058] <Production of Support Membrane Module> Eighty of the hollow fiber porous support membranes cut to a length of 120 mm were housed in a cylindrical housing made of synthetic resin with a diameter of 20 mm, and both ends were fixed with an adhesive so as not to block the hollow portions of the hollow fibers, thereby producing a module with an effective length of 80 mm and an effective membrane inner surface area of ​​0.007 m. ２ A supported membrane module was manufactured.

[0059] <Evaluation of hollow fiber forward osmosis membrane module> Evaluation was carried out in the same manner as in Example 1, except that 50% MeCN was used as the liquid containing an organic solvent. The evaluation results are shown in Table 1.

[0060] Example 4 The forward osmosis membrane housed in the hollow fiber forward osmosis membrane module in Example 4 is a forward osmosis membrane that uses a hollow fiber membrane made of polyethersulfone (PES) as the hollow fiber porous support membrane and has a polyamide separation functional layer on the inner surface of the hollow fiber membrane. In Example 4, the hollow fiber forward osmosis membrane module was manufactured in the same manner as in the Examples, except that the hollow fiber porous support membrane made of polyethersulfone (PES) and the support membrane module were each manufactured as follows.

[0061] <Production of Hollow Fiber Porous Support Membrane> As polyethersulfone (PES), a mixture of 55 parts by mass of BASF's "Ultrason E 2020 P" (trade name) and 45 parts by mass of hydroxylated terminal polyethersulfone (BASF's "Ultrason E 2020 P SR") was used. This polymer mixture was dissolved in N-methyl-2-pyrrolidone (Fujifilm Wako Pure Chemical Industries, Ltd.) to prepare a polymer solution (spinning dope) with a polymer concentration of 18.5% by mass. The spinning dope was filled into a wet hollow fiber spinning machine equipped with a double spinneret. The spinning dope was discharged from the outer spinneret of the double spinneret, and the internal coagulation liquid (water) was discharged from the inner spinneret. The dope was then introduced into a coagulation bath filled with water as the external coagulation liquid, and coagulated to obtain a hollow fiber porous support membrane. The obtained hollow fiber porous support membrane had an outer diameter of 1.0 mm, an inner diameter of 0.70 mm, and a membrane thickness of 0.15 mm.

[0062] <Production of Support Membrane Module> 115 of the hollow fiber porous support membranes cut to a length of 120 mm were housed in a cylindrical housing made of synthetic resin with a diameter of 20 mm, and both ends were fixed with an adhesive so as not to block the hollow portions of the hollow fibers. This resulted in a module with an effective length of 80 mm and an effective membrane inner surface area of ​​0.02 m. ２ A supported membrane module was manufactured.

[0063] <Evaluation of hollow fiber forward osmosis membrane module> Evaluation was carried out in the same manner as in Example 1, except that 50% MeCN was used as the liquid containing an organic solvent. The evaluation results are shown in Table 1.

[0064] Example 5 Evaluation was carried out in the same manner as in Example 1, except that EtOH was used as the liquid containing the organic solvent. The evaluation results are shown in Table 1.

[0065] Example 6 Evaluation was performed in the same manner as in Example 1, except that regeneration treatment using hot water as a regenerating agent was performed by the following method instead of regeneration treatment using superheated steam. The evaluation results are shown in Table 1. The procedure for regeneration treatment using hot water is as follows. Regeneration treatment was performed by circulating hot water at a temperature of 85°C through the space inside the hollow fibers of the module after contact with the liquid containing an organic solvent at a flow rate of 100 mL / min for 0.5 hours. Thereafter, water at 85°C was circulated through the space inside the hollow fibers of the module for 30 minutes to wash the inner surfaces of the hollow fibers after regeneration treatment, thereby completing the regeneration treatment.

[0066] Examples 7 and 8 Evaluations were performed in the same manner as in Example 6, except that the type of liquid containing an organic solvent, and the temperature and flow time of the hot water were each set as shown in Table 1. The evaluation results are shown in Table 1.

[0067] Comparative Example 1 Evaluation was carried out in the same manner as in Example 6, except that water at 25° C. was used instead of hot water and the regeneration treatment was carried out for 24 hours. The evaluation results are shown in Table 1.

[0068] Example 9 Evaluation was carried out in the same manner as in Example 3, except that toluene was used as the liquid containing an organic solvent and the module was dried by flowing dry air through the module after contact. The evaluation results are shown in Table 2.

[0069] Example 10 Evaluation was carried out in the same manner as in Example 9, except that ethyl acetate was used as the liquid containing an organic solvent and the module was dried by flowing dry air through the module after contact. The evaluation results are shown in Table 2.

[0070] Example 11 Evaluation was carried out in the same manner as in Example 5, except that the module was dried by flowing dry air through it after contact with EtOH as a liquid. The evaluation results are shown in Table 2.

[0071]

[0072]

Claims

1. A method for regenerating a semipermeable membrane, comprising: the semipermeable membrane has a history of contact with a liquid containing an organic solvent, The regeneration method includes contacting the semipermeable membrane with a regenerant; The regenerant is selected from a water-containing liquid having a temperature of 50°C or higher and a water-containing gas having a temperature of 80°C or higher; The semipermeable membrane has a support membrane and a separation functional layer, and A method for regenerating a semipermeable membrane, wherein the separation functional layer comprises polyamide.

2. The method for regenerating a semipermeable membrane according to claim 1, wherein the semipermeable membrane is a forward osmosis membrane.

3. The method for regenerating a semipermeable membrane according to claim 1 or 2, wherein the regenerant is water vapor at a temperature of 100°C or higher and 140°C or lower.

4. The method for regenerating a semipermeable membrane according to claim 1 or 2, wherein the regenerant is water at a temperature of 70°C or higher and 100°C or lower.

5. 2. The method for regenerating a semipermeable membrane according to claim 1, wherein the contact time between the semipermeable membrane and the regenerating agent is 2 minutes or more and 10 hours or less.

6. The method for regenerating a semipermeable membrane according to claim 3, wherein the contact time between the semipermeable membrane and the regenerating agent is from 2 minutes to 10 hours.

7. The method for regenerating a semipermeable membrane according to claim 4, wherein the contact time between the semipermeable membrane and the regenerating agent is from 2 minutes to 10 hours.

8. The method for regenerating a semipermeable membrane according to claim 1 or 2, wherein the organic solvent contained in the liquid is a hydrophilic organic solvent.

9. The method for regenerating a semipermeable membrane according to claim 8, wherein the liquid is an aqueous solution containing the hydrophilic organic solvent, and the concentration of the hydrophilic organic solvent in the liquid is 20 mass% or more based on the total mass of the liquid.

10. 3. The method for regenerating a semipermeable membrane according to claim 1 or 2, wherein the regeneration method comprises contacting the semipermeable membrane with water at a temperature below 50°C before contacting the semipermeable membrane with a regenerating agent.

11. 3. The method for regenerating a semipermeable membrane according to claim 1 or 2, wherein the semipermeable membrane has a history of contact with a treatment agent selected from a water-containing liquid at 50°C or higher and a water-containing gas at 80°C or higher before contacting with the liquid.

12. the semipermeable membrane is a forward osmosis membrane, The forward osmosis membrane was sandwiched between water and a 3.5% by mass aqueous solution of sodium chloride on one side and the other side, respectively, and forward osmosis treatment was performed. The salt back diffusion amount (R, unit: g / (m ２ × hr) and water permeability (F, unit: kg / (m ２ The forward osmosis performance value (F / R) expressed as the ratio of the forward osmosis performance value (F × hr) to the forward osmosis performance value (F ０ / R ０ ) is 0.90 times or less compared to A method for regenerating a semipermeable membrane according to claim 1 or 2.

13. the semipermeable membrane is a forward osmosis membrane, The forward osmosis membrane after regeneration by the regeneration method was sandwiched between water on one side and a 3.5 mass % aqueous sodium chloride solution on the other side, and forward osmosis treatment was performed. The salt back diffusion amount (R, unit: g / (m ２ × hr) and water permeability (F, unit: kg / (m ２ The forward osmosis performance value (F / R) expressed as the ratio of the forward osmosis performance value (F × hr) to the forward osmosis performance value (F ０ / R ０ ) is 0.85 times or more compared to The method for regenerating a semipermeable membrane according to claim 2.