JP2018015694A - Cleaning agent, cleaning liquid and cleaning method of selective permeable membrane - Google Patents

Abstract

When a permselective membrane used for water treatment, particularly a permselective membrane such as a polyamide-based RO membrane contaminated with a cationic surfactant, deteriorates the performance such as permeation flux due to membrane contamination, It effectively removes contaminants that cannot be sufficiently removed by conventional cleaning agents. A selective permeable membrane cleaning agent comprising a polymer containing styrene sulfonic acid and / or styrene sulfonate as a monomer component, and a cleaning liquid comprising the same. A method of cleaning the selective permeable membrane using this cleaning agent or cleaning liquid. By using a polymer such as polystyrene sulfonic acid for a selective permeable membrane contaminated with a cationic surfactant, the affinity of the sulfonic acid group and the benzene ring for the cationic surfactant and the repulsion of the other sulfonic group to the membrane. Thus, the cationic surfactant can be peeled off from the membrane. [Selection] Figure 1

Description

  The present invention effectively improves the performance of selective permeable membranes used in the field of water treatment, particularly when reverse osmosis (RO) membranes are contaminated and the performance such as permeation flux and desalination rate decreases. The present invention relates to a selective permeable membrane cleaning agent to be recovered and a selective permeable membrane cleaning method using the same.

  Currently, as a countermeasure for the shortage of water supply worldwide, selective permeable membranes, that is, seawater using selective permeable membrane systems such as microfiltration (MF) membranes, ultrafiltration (UF) membranes, RO membranes, Brine water is being desalinated and drained. In these selective permeable membrane systems, the membrane is contaminated with various contaminants such as inorganic and organic materials, and therefore, performance degradation such as permeation flux, differential pressure, and blocking rate due to membrane contamination is a problem, and the contamination Development of a cleaning technique that effectively restores the performance of the selective permeable membrane is desired.

  In recent years, as an RO membrane for water treatment, an aromatic polyamide RO membrane capable of low-pressure operation and excellent in desalting performance has been widely used. However, since the aromatic polyamide RO membrane has low resistance to chlorine, it cannot be treated with chlorine under operating conditions like the cellulose acetate RO membrane, and contamination by microorganisms and organic matter is not acetic acid. There is a problem that it is more likely to occur than a cellulosic RO membrane. On the other hand, the resistance against alkali is higher in the aromatic polyamide RO membrane than in the cellulose acetate RO membrane, and it is possible to perform cleaning under alkaline conditions of pH 10 or higher.

As such an alkali-resistant aromatic polyamide RO membrane, conventionally known cleaning agents effective for membrane contaminants such as microorganisms and organic substances include the following (Non-patent Document 1).
・ Alkaline agents (such as sodium hydroxide)
・ Anionic surfactant (sodium dodecylbenzenesulfonate, sodium lauryl sulfate, etc.)
・ Chelating agents (EDTA, etc.)

  However, when the RO membrane is severely contaminated, there may be a case where the above-mentioned chemicals cannot be sufficiently cleaned.

  For example, in wastewater recovery systems, when raw water contains a lot of organic matter and RO membranes are used for treatment of such raw water, organic matter adheres and the cleaning effect is insufficient even when the above conventional cleaning chemicals are used. There are cases. In particular, when a cationic surfactant is the main cause of membrane clogging, it is very difficult to restore membrane performance with the above conventional cleaning agents.

  Typical cationic surfactants contained in the raw water of the wastewater recovery system are shown below. These cationic surfactants are used in antistatic agents, softeners, inverse soaps, disinfectants, disinfectants, pharmaceuticals, etc., and are included in the raw water for RO membrane treatment. The cationic surfactant has a cationic quaternary ammonium group as a hydrophilic group and an alkyl group or a benzene ring as a hydrophobic group.

  Sodium hypochlorite is a powerful cleaning agent for organic substances. However, as described above, since the aromatic polyamide RO membrane has low resistance to chlorine, sodium hypochlorite is an aromatic polyamide. It is rarely used for cleaning system RO membranes. In general, when a chlorine-based disinfectant is used, it is known that free chlorine is reduced using a reducing agent and then supplied to the RO membrane (Patent Document 1).

  There are several cases where an organic solvent such as ethanol or ethylene glycol monomethyl ether is used as the cleaning agent component for the RO membrane. For example, Patent Document 2 describes a cleaning method in which a hydrophilic organic solvent such as ethanol or methanol and a surfactant are combined. However, ethanol and methanol have low flash points and are not practical. Patent Document 3 describes a cleaning agent using an alkyl ether of ethylene glycol. However, since ethylene glycol alkyl ethers have hydrophilic and hydrophobic groups and have a structure close to that of monohydric alcohol, they are highly harmful and have a strong irritating odor. The working environment evaluation value is also 5 mg / L or less, and there is a problem that the use concentration cannot be increased. Patent Document 4 proposes a cleaning agent containing a polyol having a molecular weight of 400 or less, and Patent Document 5 proposes a cleaning agent containing ethylene glycol or propylene glycol. For cleaning an RO membrane contaminated with a nonionic surfactant. It is described that this is effective. However, effectiveness is not shown for RO membranes contaminated with a cationic surfactant. For example, propylene glycol does not provide a sufficient cleaning effect as shown in Comparative Example 2 below.

  In addition, MF membranes and UF membranes generally have a neutral to negative surface charge and have a high risk of contamination with cationic surfactants, but there are few reports of effective cleaning methods at present. It is.

JP-A-9-57067 Japanese Patent Laid-Open No. 58-8502 JP-A-55-51406 Japanese Patent No. 4458039 Japanese Patent No. 4691970

"Membrane degradation and fouling countermeasures: From membrane contamination prevention and cleaning methods to troubleshooting" (NTS issue) p142 2008

  The present invention effectively removes contaminants that cannot be sufficiently removed by conventional cleaning agents when the permselective membrane used in water treatment becomes contaminated and performance such as permeation flux decreases. A selective permeation membrane cleaning agent and cleaning liquid that can be used, and a cleaning method for a selective permeation membrane using the same, and particularly a cleaning agent, a cleaning liquid, and a cleaning method that are effective when the cationic surfactant is a contaminant The task is to do.

  In order to solve the above problems, the present inventors have obtained and prepared various selective permeable membranes contaminated with a cationic surfactant, and as a result of earnestly examining effective detergent components, styrene sulfonic acid and / or styrene. A polymer having a sulfonate salt (hereinafter sometimes referred to as “styrene sulfonic acid (salt)”) as a monomer component (hereinafter sometimes referred to as “styrene sulfonic acid (salt) -based polymer”) is excellent in washing. It is important that benzenesulfonic acid or p-toluenesulfonic acid has no cleaning effect even if it has the same structure as styrenesulfonic acid, and is a polymer of styrenesulfonic acid (salt). I found out.

  The present invention has been achieved on the basis of such findings, and the gist thereof is as follows.

[1] A selective permeable membrane cleaning agent comprising a polymer containing styrene sulfonic acid and / or styrene sulfonate as a monomer component.

[2] The selective permeable membrane cleaning agent according to [1], wherein the polymer is a homopolymer of styrene sulfonic acid or styrene sulfonate.

[3] The selective permeable membrane cleaning agent according to [1] or [2], wherein the selective permeable membrane is a reverse osmosis membrane.

[4] The selective permeable membrane cleaning agent according to [3], wherein the reverse osmosis membrane is a polyamide-based reverse osmosis membrane.

[5] The selective permeable membrane cleaning agent according to any one of [1] to [4], further comprising an anionic surfactant.

[6] The selective permeation membrane cleaning agent according to any one of [1] to [5], further comprising a compound having an amide bond.

[7] A selective permeable membrane cleaning solution comprising the selective permeable membrane cleaner according to any one of [1] to [6] and having a pH of 10 or more or 4 or less.

[8] The selective permeable membrane cleaning agent using the selective permeable membrane cleaning agent according to any one of [1] to [6] or the selective permeable membrane cleaning solution according to [7]. Method.

  According to the present invention, a selective permeable membrane such as an RO membrane contaminated by being used in water treatment, particularly a selective permeable membrane having a reduced performance such as a permeation flux due to contamination with a cationic surfactant. On the other hand, by using a styrene sulfonic acid (salt) -based polymer, it is possible to effectively remove contaminants that cannot be sufficiently removed by a conventional cleaning agent and to restore the membrane performance.

It is a schematic diagram explaining the action mechanism of the cleaning effect of the present invention, and (a) shows the adsorption action of benzenesulfonic acid on the membrane adsorbed with the cationic surfactant (benzalkonium chloride), (b) FIG. Shows the peeling action of polystyrene sulfonic acid. It is a schematic diagram which shows the structure of the flat membrane test apparatus used in the Example. It is sectional drawing which shows the structure of the airtight container of the flat membrane test apparatus of FIG.

  Hereinafter, embodiments of the present invention will be described in detail.

[Action mechanism]
First, the action mechanism of the cleaning effect by the styrene sulfonic acid (salt) polymer according to the present invention will be described with reference to FIG. FIG. 1 shows a state in which benzalkonium chloride (in FIG. 1, R represents an alkyl group having 8 to 18 carbon atoms) is adsorbed to the membrane M as a cationic surfactant.

  As described above, most of the cationic surfactants contained in the raw water of the wastewater recovery system have a cationic quaternary ammonium group as a hydrophilic group and an alkyl group or a benzene ring as a hydrophobic group. On the other hand, the selective permeable membrane has a weak and negative charge due to the presence of a carboxyl group or the like. Therefore, as shown in FIG. 1A, the positive charge of the cationic surfactant (benzalkonium chloride) is positive. As a pair, the cationic surfactant is adsorbed on the membrane M. In addition, since the aromatic polyamide RO membrane has a benzene ring in its skeleton, it also has an interaction with the hydrophobic group of the cationic surfactant.

  Since benzenesulfonic acid (salt) has a sulfone group and a benzene ring, it is considered to have a high affinity with a cationic surfactant. As shown in FIG. Easy to adsorb to the activator. As shown in FIG. 1 (a), it is not adhering to the cationic surfactant adsorbed on the membrane M, but it is not peeled off. For example, in the case of polystyrene sulfonic acid which is a polymer of styrene sulfonic acid, When a pair of sulfone groups and a benzene ring are adsorbed on the cationic surfactant, as shown in FIG. 1B, other sulfone groups in the polymer repel the membrane M and adsorbed cationic surface activity. It is considered that there is an effect such as nail pulling away from the membrane M with the agent. For this reason, by using a styrene sulfonic acid (salt) -based polymer such as polystyrene sulfonic acid, it becomes possible to effectively wash the RO membrane contaminated with the cationic surfactant.

  When the cationic surfactant is peeled off, the presence of the anionic surfactant has an effect of relaxing the adsorption force of the cationic surfactant on the membrane. In addition, the compound having an amide bond has particularly strong affinity with the surface of the polyamide RO membrane, and has an effect of substituting with a cationic surfactant. Therefore, the combined use of these agents and the styrene sulfonic acid (salt) polymer can synergistically improve the cleaning effect.

[Selective permeable membrane]
In the present invention, the selective permeable membrane to be cleaned may be a selective permeable membrane used in water treatment such as a wastewater recovery system, and includes RO membrane, UF membrane, MF membrane, etc. It is effective for cleaning RO membranes, particularly aromatic polyamide RO membranes which have low resistance to chlorine and cannot be cleaned with sodium hypochlorite. In addition, the present invention is particularly effective for a selective permeable membrane that is used for wastewater treatment and is contaminated with a cationic surfactant, so that a sufficient cleaning effect cannot be obtained with a conventional cleaning agent. In this case, examples of the cationic surfactant that becomes a membrane contaminant include the aforementioned benzalkonium chloride, benzethonium chloride, hexadecyltrimethylammonium bromide, cetylpyridinium chloride, and decalinium chloride, but are not limited thereto. It is not something.

[Cleaning agent for selective permeable membrane]
The selective permeable membrane cleaning agent of the present invention (hereinafter sometimes referred to as “the cleaning agent of the present invention”) is characterized by containing a styrene sulfonic acid (salt) -based polymer, and is usually styrene. A sulfonic acid (salt) polymer, an alkali agent or acid agent, an anionic surfactant, a compound having an amide bond (hereinafter sometimes referred to as “amide compound”), other agents and solvents, which are used as necessary. Etc. are dissolved in water.
In the present invention, “cleaning agent” is a product prepared by setting the concentration of styrene sulfonic acid (salt) -based polymer or other chemicals higher than in use for the distribution and storage of products. By the way, the “cleaning solution” refers to a solution obtained by diluting this cleaning agent with water and adjusting the concentration to actually clean the film surface.

<Styrene sulfonic acid (salt) -based polymer>
The styrene sulfonic acid (salt) polymer used in the present invention is a polymer containing styrene sulfonic acid (salt) as a monomer component, that is, a polymer having a repeating unit derived from styrene sulfonic acid (salt) in the polymer. It may be a homopolymer of sulfonic acid (salt) or a copolymer of styrene sulfonic acid (salt) and other monomers.
Examples of the styrene sulfonate include alkali metal salts of styrene sulfonic acids such as sodium styrene sulfonate and potassium styrene sulfonate, alkaline earth metal salts, ammonium salts, and the like.

  When the styrene sulfonic acid (salt) -based polymer used in the present invention is a copolymer of styrene sulfonic acid (salt) and another monomer, the other monomer can be copolymerized with styrene sulfonic acid (salt). There is no particular limitation as long as it does not inhibit the adsorption to the cationic surfactant by the styrene sulfonic acid (salt) -based polymer and the peeling action of the cationic surfactant from the film, but there is no particular limitation, for example, acrylic acid, One type or two or more types of acrylic acid ester, acrylamide, vinyl acetate, allylamine, maleic acid and the like can be mentioned.

  However, adsorption to the cationic surfactant by the styrene sulfonic acid (salt) -based polymer and release action of the cationic surfactant from the membrane are the sulfones derived from styrene sulfonic acid (salt) in the styrene sulfonic acid (salt) -based polymer. In order to effectively obtain this effect, the styrene sulfonic acid (salt) -based polymer preferably has a large content of repeating units derived from styrene sulfonic acid (salt). When the sulfonic acid (salt) -based polymer is a copolymer of styrene sulfonic acid (salt) and another monomer, the content of repeating units derived from styrene sulfonic acid (salt) in the styrene sulfonic acid (salt) -based polymer is It is preferably 50 mol% or more, particularly 80 mol% or more. The styrene sulfonic acid (salt) -based polymer is It is preferably a homopolymer of acid (salt). Here, the homopolymer of styrene sulfonic acid (salt) includes not only polystyrene sulfonic acid and polystyrene sulfonate, but also a copolymer of styrene sulfonic acid and styrene sulfonate.

  Although there is no restriction | limiting in particular in the molecular weight of a styrenesulfonic acid (salt) type polymer, It is preferable that it is 1000 or more by weight average molecular weight by gel permeation chromatography (GPC), and it is more preferable that it is 4000 or more. On the other hand, the molecular weight of the styrene sulfonic acid (salt) -based polymer is preferably 5 million or less, and more preferably 1.2 million or less. When the molecular weight of the styrene sulfonic acid (salt) polymer is not less than the above lower limit, it is preferable from the viewpoint of adsorption of the cationic surfactant and peeling from the film, and when it is not more than the above upper limit, from the viewpoint of diffusibility as a cleaning agent. preferable.

  The cleaning agent for a selective permeable membrane of the present invention may contain only one kind of styrene sulfonic acid (salt) -based polymer, and contains two or more kinds having different monomer components, monomer compositions, molecular weights and the like. It may be.

<Anionic surfactant>
The cleaning agent of the present invention may contain an anionic surfactant, and by containing the anionic surfactant, as described above, the adsorptive power to the membrane of the cationic surfactant is relaxed and more excellent. The peeling cleaning effect can be obtained.

  Examples of the anionic surfactant include alkyl benzene sulfonates such as sodium dodecyl benzene sulfonate and alkyl sulfates such as sodium dodecyl sulfate. The cleaning agent of the present invention may contain only one of these anionic surfactants, or may contain two or more.

<Amide compound>
The cleaning agent of the present invention may contain an amide compound. By including the amide compound, as described above, the polyamide RO membrane has a good peeling cleaning effect due to the substitution action with the cationic surfactant. Can be obtained.

  The amide compound is preferably water-soluble from the viewpoint of affinity with the polyamide-based RO membrane, and has a molecular weight of 300 or less from the viewpoint of penetrating between the RO membrane and the contaminant and exhibiting a good cleaning effect. In particular, those having a relatively low molecular weight of 200 or less are preferred. If the molecular weight of the amide compound is too large, it may be difficult to penetrate between the RO membrane and the contaminant, and a good cleaning effect may not be obtained.

  From the viewpoint of the cleaning effect, the amide compound is preferably a compound represented by the following formula (I).

(In formula (I), R ₁₁ represents a hydrogen atom, or an alkyl group having 1 to 3 carbon atoms, a heterocyclic group or an aromatic group, each of which may have a substituent, and R ₁₂ represents a hydrogen atom, or (It represents an alkyl group having 1 to 3 carbon atoms which may have a substituent, and R ₁₃ represents a hydrogen atom or an alkyl group having 1 to 3 carbon atoms.)

In the above formula (I), examples of the substituent that the alkyl group of R ₁₁ may have include a carboxyl group (—COOH), an amino group (—NH ₂ ), and a hydroxy group (—OH). As the heterocyclic group, an N-containing unsaturated heterocyclic group is preferable, and specific examples include a pyridyl group, an imidazolyl group, an indolyl group, a thiazolyl group, a triazinyl group, a pyrazinyl group, and a pyrimidinyl group. Examples of the aromatic group include aromatic hydrocarbon groups such as a phenyl group, a naphthyl group, and an indenyl group. These heterocyclic groups and aromatic groups have a carboxyl group (—COOH), amino group (—NH ₂ ), aminocarbonyl group (—CONH ₂ ), hydroxy group (—OH), alkyl group (—C) as substituents. _n H _{2n + 1} ) and the like.

Examples of the substituent that the alkyl group of R ₁₂ may have include a carboxyl group (—COOH), an amino group (—NH ₂ ), and a hydroxy group (—OH).

  Specific examples of the amide compound include the following.

  Among these amide compounds, in particular, aliphatic amides include asparagine, glutamine, formamide, acetamide, N, N-dimethylformamide, N, N-dimethylacetamide, and aromatic amides include nicotinamide, benzamide, amino Preferred examples include benzamide, phthalamide and hippuric acid.

  The cleaning agent of the present invention may contain only one of these amide compounds, or may contain two or more.

<Alkaline agent / Acid agent>
The cleaning agent of the present invention may contain an alkali agent or an acid agent in order to adjust the pH range so that an excellent cleaning effect can be obtained when used as a cleaning liquid.
As the alkali agent, alkali metal hydroxides such as sodium hydroxide and potassium hydroxide can be used.
As the acid agent, inorganic acids and organic acids such as nitric acid, sulfuric acid, hydrochloric acid, oxalic acid, and citric acid can be used.

<Other ingredients>
In addition to the above components, the cleaning agent of the present invention may contain other cleaning agents and solvents necessary for RO membrane cleaning.

For example, nonionic surface activity such as polyalkylene glycol monoalkyl ether such as diethylene glycol monomethyl ether, ethylenediaminetetraacetic acid (EDTA), glycoletherdiaminetetraacetic acid (EGTA), polyphosphoric acid, phosphonobutanetricarboxylic acid (PBTC), A dispersing agent such as a chelating agent such as phosphonic acid, polymaleic acid, citric acid, oxalic acid, gluconic acid and salts thereof may be contained.
All of these may contain only one type, or two or more types.

  The cleaning agent of the present invention includes, as a solvent, alcohols such as ethanol, polyols such as ethylene glycol, propylene glycol and butanediol, amines such as monoethanolamine, diethanolamine and triethanolamine, and ketones such as acetone. 1 type, or 2 or more types, such as ethers, such as dimethyl ether, diethyl ether, and diethylene glycol monomethyl ether, may be included.

<Form of cleaning agent>
The cleaning agent of the present invention may be a one-agent type in which a styrene sulfonic acid (salt) polymer, an alkali agent or an acid agent, a cleaning agent, etc. are mixed in advance, and a part of these is supplied as another agent. It may be a two-drug type or a dosage form of more than that.
Accordingly, the selective permeation membrane cleaning liquid of the present invention prepared by diluting the cleaning agent of the present invention with water may be of one-drug type, two-drug type, or more. Good. In the case of a two-drug type or more, for example, the membrane may be washed with a cleaning solution containing a styrene sulfonic acid (salt) -based polymer and then washed with a cleaning solution containing another cleaning agent.

When the detergent of the present invention is diluted to about 5 to 100 times by weight with water, preferably pure water, the concentration of each drug is such that the concentration of each drug is suitable for the cleaning liquid of the present invention described later. It is prepared to be about 5 to 100 times the drug concentration in
The cleaning agent of the present invention is prepared as an aqueous solution, or all or part of it as a powder or solid.

[Cleaning liquid for selective permeable membrane]
The selective permeable membrane cleaning solution of the present invention (hereinafter sometimes referred to as “the cleaning solution of the present invention”) is an aqueous solution obtained by diluting the above-described cleaning agent of the present invention with water. The cleaning solution of the present invention is prepared by diluting the cleaning agent of the present invention with water and, if necessary, adding an alkali agent or acid agent, another cleaning agent, a solvent or the like to a predetermined concentration. There may be.
However, the cleaning liquid of the present invention may be prepared directly to a predetermined drug concentration without passing through the cleaning agent of the present invention.

  The concentration of the styrene sulfonic acid (salt) -based polymer in the cleaning liquid of the present invention is the type of styrene sulfonic acid (salt) -based polymer used, the pH of the cleaning liquid, the presence or absence of other cleaning chemicals, the type and concentration, Depending on the degree of contamination of the membrane to be cleaned, etc., the polystyrene sulfonic acid concentration is preferably about 0.01 to 10% by weight, particularly preferably about 0.1 to 5% by weight. If the styrene sulfonic acid (salt) polymer concentration is lower than the above lower limit, it is not possible to sufficiently obtain a membrane cleaning effect by using the styrene sulfonic acid (salt) polymer, and the styrene sulfonic acid (salt) polymer concentration Even if it is higher than the above upper limit, the cleaning effect corresponding to the concentration cannot be obtained, and the sulfur content of the cleaning waste liquid is unnecessarily increased.

The cleaning liquid of the present invention is preferably adjusted to alkali or acid in terms of the cleaning effect. When making it alkaline, it is preferable that pH is 10 or more, especially 10-14.
If the pH of the cleaning liquid is less than 10, the permeability of the membrane may not be sufficiently recovered by cleaning. The higher the pH of the cleaning solution is, the better the cleaning effect is. However, if the cleaning solution is too high, the handling property as the cleaning solution becomes poor and the risk of deterioration of the film increases. Therefore, the pH of the cleaning solution is preferably 14 or less, more preferably 11 It is 13 or less.
In the case of acidity, the pH is 4 or less, preferably 0 to 3. If it is this range, sufficient cleaning effect will be acquired.

Therefore, it is preferable that the cleaning liquid of the present invention is prepared so as to have the above-mentioned preferable pH by adding the alkali agent or acid agent described above.
However, when applied to the washing of cellulose acetate membrane, the pH is preferably less than 8.

  When the cleaning liquid of the present invention contains an anionic surfactant, the concentration of the anionic surfactant in the cleaning liquid of the present invention is preferably 0.01 to 2% by weight, particularly 0.05 to 0.5% by weight. Preferably there is. If the concentration of the anionic surfactant is too low, the effect of improving the cleaning action by the anionic surfactant cannot be obtained sufficiently, and if it is too high, the association of the anionic surfactant may be strengthened and the cleaning effect may be lowered. .

  When the cleaning liquid of the present invention contains an amide compound, the concentration of the amide compound in the cleaning liquid of the present invention is preferably 0.1 to 10% by weight, particularly preferably 0.5 to 5% by weight. If the amide compound concentration is too low, the effect of improving the cleaning action by the amide compound cannot be obtained sufficiently, and if it is too high, the cleaning effect corresponding to the concentration cannot be obtained.

  It is not preferable in terms of cleaning waste liquid treatment that both the anionic surfactant and the amide compound are too high in the cleaning liquid.

<Selective Permeation Membrane Cleaning Agent and Cleaning Liquid Manufacturing Method>
The cleaning agent of the present invention is prepared by mixing styrene sulfonic acid (salt) -based polymer with water and an alkali agent or acid agent, a cleaning agent, other solvents, and the like that are blended as necessary. Alternatively, all or a part thereof may be prepared as a powder or a solid.

  The cleaning solution of the present invention is prepared by diluting the thus prepared cleaning agent of the present invention with water, preferably pure water, and adding an alkali agent or acid agent, other cleaning agents, solvents, etc. as necessary. Manufactured. However, the cleaning liquid of the present invention can also be produced directly by the same method as above without passing through the cleaning agent of the present invention.

<Washing method>
The method for cleaning the selective permeable membrane using the cleaning liquid of the present invention is not particularly limited as long as the selective permeable membrane is brought into contact with the cleaning liquid. Usually, immersion cleaning is performed in which a cleaning liquid is introduced and allowed to stand on the raw water side of the selective permeable membrane module. Moreover, you may perform the circulation washing | cleaning which circulates a washing | cleaning liquid before and / or after this immersion washing.

  In addition, when the cleaning agent and the cleaning liquid of the present invention are two or more types, they may be mixed and used for cleaning, or may be cleaned sequentially using different agents. Good. For example, after washing with a cleaning liquid containing a styrene sulfonic acid (salt) -based polymer, it may be cleaned with a cleaning liquid containing other chemicals.

  In addition, when performing other cleaning, for example, cleaning using an alkaline aqueous solution or an acid aqueous solution, before and after cleaning with the cleaning liquid of the present invention, the same immersion cleaning as described above, or immersion cleaning and circulation cleaning are usually employed. Is done.

  Here, as cleaning with a cleaning liquid other than the cleaning liquid of the present invention, cleaning with an alkaline aqueous solution not containing a styrenesulfonic acid (salt) -based polymer can be performed after cleaning with the cleaning liquid of the present invention. As the alkaline agent of the alkaline aqueous solution, those described above as the alkaline agent used in the cleaning liquid of the present invention can be used. The pH of the alkaline aqueous solution is preferably pH 10 or higher, particularly pH 11 to 13 in terms of cleaning effect and handleability.

  In addition, acid cleaning effective for removing scales and metal colloids may be performed. For the acid cleaning, an aqueous solution containing one or more acids such as sulfuric acid, hydrochloric acid, nitric acid, citric acid, and oxalic acid is used. be able to. The pH of the acid aqueous solution is preferably 4 or less from the viewpoint of cleaning effect and handleability, and is preferably lower as long as there is no damage to the membrane. This is because the lower the pH, the more the charge of the membrane goes in the positive direction, and the cationic surfactant becomes easier to peel off.

  The immersion cleaning time with the cleaning liquid of the present invention and other cleaning liquids is not particularly limited as long as the recovery rate of the target film performance can be obtained, but is usually about 2 to 24 hours. In addition, when performing circulation cleaning before and after immersion cleaning, the circulation cleaning time is not particularly limited as long as the desired recovery rate of the membrane performance can be obtained, but is usually about 0.5 to 3 hours. It is.

  When the cleaning with the cleaning liquid of the present invention is combined with the cleaning with the aqueous alkali solution and / or the aqueous acid solution, the cleaning procedure is not particularly limited. When the acid cleaning with the acid aqueous solution is performed before the cleaning with the cleaning liquid of the present invention, it is effective for removing scale components.

  After washing with the above-described washing liquid, finishing washing is usually performed by passing high-purity water such as pure water. Thereafter, the operation of the selective permeable membrane system is resumed.

  Hereinafter, the present invention will be described more specifically with reference to Examples and Comparative Examples.

In the following examples and comparative examples, the cleaning effect of the RO membrane was examined using the flat membrane test apparatus shown in FIGS.
In this flat membrane test apparatus, RO membrane supply water is supplied from a pipe 11 by a high-pressure pump 4 to the raw water chamber 1A below the flat membrane unit 2 in which the RO membrane of the sealed container 1 is set. As shown in FIG. 3, the sealed container 1 is composed of a lower case 1a on the raw water chamber 1A side and an upper case 1b on the permeate water chamber 1B side, and a flat membrane is formed between the lower case 1a and the upper case 1b. The unit 2 is fixed via an O-ring 8. The flat membrane unit 2 is configured such that the permeate side of the RO membrane 2A is supported by the porous support plate 2B. The raw water chamber 1 </ b> A below the flat membrane unit 2 is agitated by rotating the stirrer 5 with a stirrer 3. The RO membrane permeate is taken out from the pipe 12 through the permeate chamber 1B on the upper side of the flat membrane unit 2. The concentrated water is taken out from the pipe 13. The pressure in the sealed container 1 is adjusted by a pressure gauge 6 provided in the water supply pipe 11 and a pressure adjusting valve 7 provided in the concentrated water outlet pipe 13.

As a test membrane, an aromatic polyamide RO membrane (flat membrane) “ES20” manufactured by Nitto Denko Co., Ltd. was used by cutting it into a circle, and this was set in the above-mentioned flat membrane test apparatus, and the initial pure water permeation flux: After measuring J0 [m ³ / (m ² · d)], simulated raw water having a cationic surfactant concentration of 1 mg / L was passed for 65 hours to cause membrane contamination, and the pure water permeation flux of the contaminated membrane was J1 [ m ³ / (m ² · d)] was measured. Thereafter, the contaminated film was immersed in each cleaning solution for 16 hours, rinsed with pure water, and then measured for pure water permeation flux: J2 [m ³ / (m ² · d)]. From these measured values, the contamination rate and the recovery rate were determined by the following equations. This water flow test was performed at 25 ° C. and 0.75 MPa.
Contamination rate [%] = (J1 / J0) × 100
Recovery rate [%] = (J2 / J0) × 100

In addition, pH adjustment of the washing | cleaning liquid by sodium hydroxide was performed by diluting and using 6N sodium hydroxide aqueous solution (made by Kishida-Chemical company) suitably. The pH adjustment with nitric acid was performed by appropriately diluting 60% by weight nitric acid (manufactured by Kishida Chemical Co., Ltd.).
Cationic surfactants include benzalkonium chloride (manufactured by Kishida Chemical Co., Ltd.), benzethonium chloride (manufactured by Wako Pure Chemical Industries, Ltd.), hexadecyltrimethylammonium bromide (manufactured by Wako Pure Chemical Industries, Ltd.), cetylpyridinium chloride (Wako Pure Chemical Industries, Ltd.) Yakuhin Kogyo Co., Ltd.) and decalinium chloride (Wako Pure Chemical Industries, Ltd.) were used.

As the styrene sulfonic acid (salt) -based polymer, the following were used.
Polystyrene sulfonate sodium having a molecular weight of 4,300: manufactured by Sigma-Aldrich Corporation Polystyrene sulfonate sodium having a molecular weight of 1 to 30,000: “Polynas PS-1” manufactured by Tosoh Corporation
Polystyrene sulfonic acid having a molecular weight of 70,000: manufactured by Polysciences Ammonium polystyrene sulfonate having a molecular weight of 200,000: manufactured by Sigma-Aldrich Co., Ltd. Sodium polystyrene sulfonate having a molecular weight of 80 to 1,200,000: “Polynas PS-100” manufactured by Tosoh Corporation

  As the anionic surfactant, sodium dodecylbenzenesulfonate (manufactured by Tokyo Chemical Industry Co., Ltd.) was used, and as the amide compound, nicotinamide (manufactured by Kishida Chemical Co., Ltd.) was used.

Moreover, the following were used as cleaning chemicals for comparison.
Propylene glycol: Copolymer of acrylic acid and 2-acrylamido-2-methylpropanesulfonic acid manufactured by Kishida Chemical Co., Ltd .: “Accusol 587” manufactured by Dow Chemical Co., Ltd., molecular weight 11,000, acrylic acid: 2-acrylamido-2-methylpropanesulfonic acid = 81: 19 (molar ratio) (hereinafter referred to as “AA / AMPS copolymer”)
Sodium benzenesulfonate monohydrate: Wako Pure Chemical Industries, Ltd. p-Toluenesulfonic acid monohydrate: Wako Pure Chemical Industries, Ltd.

[Examples 1-5, Comparative Examples 1-5]
Benzalkonium chloride was used as the cationic surfactant, the following were used as the cleaning solutions, the contamination rate and the recovery rate were determined, and the results are shown in Table 1.
Comparative Example 1: pH 12 sodium hydroxide aqueous solution Comparative Example 2: pH 12 sodium hydroxide aqueous solution containing 2 wt% propylene glycol Comparative Example 3: pH 12 sodium hydroxide aqueous solution containing 0.6 wt% AA / AMPS copolymer Comparative Example 4: A sodium hydroxide aqueous solution having a pH of 12 containing 0.6% by weight sodium benzenesulfonate monohydrate (concentration as benzenesulfonic acid) Comparative Example 5: 0.6% by weight p-toluenesulfonic acid PH 12 sodium hydroxide aqueous solution containing monohydrate (concentration as p-toluenesulfonic acid)

Example 1: A sodium hydroxide aqueous solution at pH 12 containing 0.6% by weight sodium polystyrene sulfonate (molecular weight 4,300) (concentration as polystyrene sulfonic acid) Example 2: 0.6% by weight sodium polystyrene sulfonate ( PH 12 sodium hydroxide aqueous solution containing molecular weight 1-30 thousand (concentration as polystyrene sulfonic acid) Example 3: pH 12 sodium hydroxide aqueous solution containing 0.6 wt% polystyrene sulfonic acid (molecular weight 70,000) Example 4: Sodium hydroxide aqueous solution at pH 12 containing 0.6 wt% ammonium polystyrenesulfonate (molecular weight 200,000) (concentration as polystyrenesulfonic acid) Example 5: 0.6 wt% sodium polystyrenesulfonate (molecular weight 80) ~ 1.2 million) (as polystyrene sulfonic acid Aqueous sodium hydroxide pH12 containing concentration)

  As is clear from Table 1, in Examples 1 to 5 according to the present invention, a recovery rate of 44% or more was obtained, whereas in Comparative Example 1 which is normal alkali cleaning, only 34% was recovered. It was. Even in Comparative Example 2 in which the polyol was washed, the recovery rate was 41%. In Comparative Example 3 using a polymer having a sulfone group and Comparative Examples 4 and 5 using a low molecular weight simple substance having a sulfone group in the benzene ring, the recovery rate was 40% or less.

[Examples 6 and 7 and Comparative Example 6 (combination effect of anionic surfactant and amide compound)]
In Example 1, a water flow test was conducted in the same manner except that the following cleaning liquid was used. Similarly, the contamination rate and the recovery rate were obtained, and the results are shown in Table 2.

Comparative Example 6: pH 12 sodium hydroxide aqueous solution containing 0.15 wt% sodium dodecylbenzene sulfonate Example 6: 0.6 wt% polystyrene sulfonic acid (molecular weight 70,000) and 0.15 wt% dodecyl benzene sulfonic acid PH 12 sodium hydroxide aqueous solution containing sodium Example 7: pH 12 containing 0.6 wt% polystyrene sulfonic acid (molecular weight 70,000), 0.15 wt% sodium dodecylbenzenesulfonate, and 2 wt% nicotinamide Sodium hydroxide aqueous solution

  As is apparent from Table 2, the recovery rate was 76% in Comparative Example 6 in which cleaning was performed with an alkaline cleaning solution containing an anionic surfactant, but the recovery rate was further increased in Example 6 in which polystyrene sulfonic acid was added thereto. It improved to 89%. Further, in Example 7 in which nicotinamide as an amide compound was further added to the cleaning liquid of Example 6, 100% recovery was achieved.

[Example 8, Comparative Example 7 (Effect of pH acidic cleaning solution)]
In Example 1, a water flow test was conducted in the same manner except that the following cleaning liquid was used, and the contamination rate and the recovery rate were obtained in the same manner. The results are shown in Table 3.

Comparative Example 7: 5% by weight nitric acid aqueous solution (pH <1)
Example 8: 5 wt% aqueous nitric acid solution (pH <1) containing 0.6 wt% polystyrene sulfonic acid (molecular weight 70,000)

  As is clear from Table 3, in Comparative Example 7 in which the acid cleaning agent was washed with nitric acid, the recovery rate was 74%, but in Example 8 in which polystyrene sulfonic acid was added thereto, the recovery rate was further improved. It was 81%.

[Examples 9 to 14 and Comparative Examples 8 to 11 (cleaning effect on cationic surfactants other than benzalkonium chloride)]
In Example 1, while using what was shown in Table 4 as a cationic surfactant and using the following as a washing | cleaning liquid, a water flow test was done similarly and a contamination rate and a recovery rate were calculated | required similarly, and a result Are shown in Table 4.

Comparative Example 8: pH 12 sodium hydroxide aqueous solution Example 9: pH 12 containing 0.6 wt% polystyrene sulfonic acid (molecular weight 70,000), 0.15 wt% sodium dodecylbenzenesulfonate, and 2 wt% nicotinamide Sodium hydroxide aqueous solution

Comparative Example 9: pH 12 sodium hydroxide aqueous solution Example 10: pH 12 containing 0.6 wt% polystyrene sulfonic acid (molecular weight 70,000), 0.15 wt% sodium dodecylbenzenesulfonate, and 2 wt% nicotinamide Sodium hydroxide aqueous solution

Comparative Example 10: pH 12 sodium hydroxide aqueous solution Example 11: pH 12 containing 0.6 wt% polystyrene sulfonic acid (molecular weight 70,000), 0.15 wt% sodium dodecylbenzenesulfonate, and 2 wt% nicotinamide Sodium hydroxide aqueous solution

Comparative Example 11: pH 12 sodium hydroxide aqueous solution Example 12: pH 12 containing 0.6 wt% polystyrene sulfonic acid (molecular weight 70,000), 0.15 wt% sodium dodecylbenzenesulfonate, and 2 wt% nicotinamide Sodium hydroxide aqueous solution Example 13: pH 12 sodium hydroxide aqueous solution containing 2 wt% polystyrene sulfonic acid (molecular weight 70,000), 0.15 wt% sodium dodecylbenzenesulfonate, and 2 wt% nicotinamide Example 14: PH 12 sodium hydroxide aqueous solution containing 4 wt% polystyrene sulfonic acid (molecular weight 70,000), 0.15 wt% sodium dodecylbenzene sulfonate, and 2 wt% nicotinamide

  As is apparent from Table 4, a membrane contaminated with benzethonium chloride, hexadecyltrimethylammonium bromide, or cetylpyridinium chloride cannot obtain a sufficient recovery rate by alkaline cleaning at pH 12, but a cleaning solution containing polystyrene sulfonic acid. The recovery rate was 100%. In the case of a membrane contaminated with decalinium chloride, the pure water permeation flux was not recovered at all by alkaline cleaning at pH 12, and the recovery rate was 86% even with a cleaning liquid containing 0.6% by weight polystyrene sulfonic acid. This is considered to be because decalinium chloride has a cationic functional group at two positions. As in Examples 13 and 14, a higher recovery rate can be obtained by increasing the concentration of polystyrene sulfonic acid. It was.

DESCRIPTION OF SYMBOLS 1 Container 2 Flat membrane unit 2A RO membrane 2B Porous support plate 3 Stirrer 4 High pressure pump 5 Stirrer 6 Pressure gauge 7 Pressure adjustment valve 8 O-ring

Claims (8)

  A cleaning agent for a selective permeable membrane comprising a polymer containing styrene sulfonic acid and / or styrene sulfonate as a monomer component.   2. The selective permeable membrane cleaning agent according to claim 1, wherein the polymer is a homopolymer of styrene sulfonic acid or styrene sulfonate.   3. The selective permeable membrane cleaning agent according to claim 1, wherein the selective permeable membrane is a reverse osmosis membrane.   4. The selective permeable membrane cleaning agent according to claim 3, wherein the reverse osmosis membrane is a polyamide-based reverse osmosis membrane.   The selective permeable membrane cleaning agent according to any one of claims 1 to 4, further comprising an anionic surfactant.   6. The selective permeation membrane cleaning agent according to any one of claims 1 to 5, further comprising a compound having an amide bond.   A cleaning solution for a selective permeation membrane, comprising the cleaning agent for a selective permeation membrane according to any one of claims 1 to 6, wherein the cleaning solution has a pH of 10 or more or 4 or less.   A cleaning method for a selective permeable membrane according to any one of claims 1 to 6, or the cleaning solution for a selective permeable membrane according to claim 7.

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