JP2015097991A - Cleaning agent and cleaning method of permeable membrane - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a cleaning agent, a cleaning liquid and a cleaning method capable of removing effectively a contaminant which cannot be removed sufficiently by a conventional cleaning liquid, when a performance such as a permeation flux or a salt rejection rate is lowered since a permeable membrane used for water treatment, especially an aromatic polyamide-based RO membrane is contaminated.SOLUTION: A permeable membrane is cleaned by using a cleaning liquid comprising an aqueous solution of pH 10 or higher containing a chloramine compound, a surfactant and an alkaline agent. As the chloramine compound, a material obtained by mixing a compound having a primary amino group with hypochlorous acid and/or hypochlorite is preferable. As the surfactant, an anionic surfactant is preferable.

Description

  The present invention relates to a cleaning agent, a cleaning liquid, and a cleaning method for a permeable membrane used in the field of water treatment. Specifically, when permeation membranes such as reverse osmosis (RO) membranes, ultrafiltration (UF) membranes, microfiltration (MF) membranes become contaminated and the membrane performance such as permeation flux and rejection rate decreases, the performance The present invention relates to a cleaning agent for effectively recovering water, a cleaning liquid containing the cleaning agent, and a method for cleaning a permeable membrane using the cleaning liquid.

  At present, as a countermeasure against the global shortage of water supply, brine desalination and drainage recovery using permeable membranes such as MF, UF, and RO membranes are being carried out. In systems using these permeable membranes, performance deterioration due to contamination of the permeable membrane is a problem, and development of a cleaning technique for effectively recovering the performance of the contaminated 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.

For such alkali-resistant aromatic polyamide RO membrane, as a cleaning agent effective for membrane contaminants such as microorganisms and organic substances known conventionally,
Alkaline agent (such as sodium hydroxide)
Surfactant (such as sodium lauryl sulfate)
Chelating agents (EDTA, etc.)
(Non-Patent Document 1).

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

  Sodium hypochlorite is a powerful agent against microorganisms and organic substances, but as described above, aromatic polyamide RO membranes have low resistance to chlorine, so sodium hypochlorite is aromatic. It is not used for cleaning polyamide RO membranes. In the case of using a chlorine-based disinfectant, it is known that free chlorine is reduced using a reducing agent and then supplied to the RO membrane (Patent Document 1).

  A membrane module sterilization cleaning method has been proposed in which a membrane module is subjected to acid cleaning and then sterilized cleaning with an oxidizing agent (Patent Document 2). Although this Patent Document 2 does not describe the type of permeable membrane to be cleaned, the membrane removal rate (desalting rate) is described as 95% in the initial performance. It is thought to be a cellulose acetate RO membrane. Further, Patent Document 2 does not describe that the application to an RO membrane having a reduced permeation flux is an alkaline condition.

JP-A-9-57067 JP-A-1-307407

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

  In the present invention, when a permeation membrane used for water treatment, particularly an aromatic polyamide RO membrane is contaminated and the performance such as permeation flux and desalination rate is deteriorated, the conventional cleaning agent can sufficiently remove the permeation membrane. It is an object to provide a cleaning agent, a cleaning liquid, and a cleaning method that can effectively remove contaminants that cannot be removed.

  As a result of intensive studies to solve the above problems, the inventor of the present invention uses an chloramine compound as a chlorine-based cleaning agent component to suppress an oxidative action on a permeable membrane, thereby producing an aromatic polyamide-based RO membrane with low chlorine resistance. On the other hand, it was found that the present invention can be applied as a cleaning agent, and in that case, by using a surfactant in combination, the cleaning effect can be further enhanced by the dispersing effect of the surfactant. In the case of an alkaline aqueous solution containing a chloramine compound and a surfactant provided by the present invention, in addition to the peeling effect and hydrolysis effect under alkaline conditions, the bactericidal and organic substance decomposing effects by the chloramine compound, and further by the surfactant The dispersion effect acts synergistically to obtain a good alkali cleaning effect.

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

[1] A cleaning agent for a permeable membrane comprising an aqueous solution having a pH of 13 or more containing a chloramine compound, a surfactant and an alkali agent.

[2] The cleaning agent for a permeable membrane according to [1], wherein the aqueous solution has a pH of 13 or more and 15 or less.

[3] In [1] or [2], the concentration of the chloramine compound in the aqueous solution is 0.2 to 2M, the concentration of the surfactant is 0.01 to 1M, and the concentration of the alkaline agent is 1 to 3M. A cleaning agent for a permeable membrane, characterized by

[4] The permeable membrane cleaning agent according to any one of [1] to [3], wherein the chloramine compound contains monochlororosulmic acid.

[5] In any one of [1] to [4], the chloramine compound is one or more selected from the group consisting of a compound having a primary amino group, ammonia and an ammonium salt (hereinafter referred to as “NH ₂ system”). A permeation membrane cleaning agent obtained by mixing hypochlorous acid and / or hypochlorite.

[6] In [5], hypochlorous acid and / or hypochlorite and the NH ₂ -based compound are mixed with effective chlorine concentration (Cl ₂₎ derived from hypochlorous acid and / or hypochlorite. ) And the nitrogen atom N derived from the NH ₂ -based compound (Cl ₂ / N molar ratio) is mixed so that the molar ratio is 0.1 to 1.

[7] In [5] or [6], the NH ₂ -based compound is added and dissolved in an aqueous solution of an alkaline agent, and hypochlorous acid and / or hypochlorite is added to the obtained NH ₂ -based compound aqueous solution. A permeable membrane cleaning agent obtained through a step of adding and mixing.

[8] In [7], the aqueous solution of the alkali agent has an amount of water of 50 to 90% by weight, and the ratio of the alkali agent to the NH ₂ -based compound is 0.5 in terms of N / alkali metal (molar ratio). An NH ₂ -based compound is added so as to be ˜0.7, and hypochlorous acid and / or hypochlorite is added as an aqueous solution having an effective chlorine (Cl ₂ ) concentration of 5 to 20% by weight. Permeable membrane cleaner.

[9] The cleaning agent for a permeable membrane according to any one of [1] to [8], wherein the surfactant is an anionic surfactant having a molecular weight of 1000 or less.

[10] The cleaning agent for a permeable membrane according to [9], wherein the anionic surfactant is one or more selected from the group consisting of alkylbenzene sulfonate and alkyl sulfate.

[11] A permeable membrane cleaning solution comprising an aqueous solution having a pH of 10 or higher, which is obtained by diluting the permeable membrane cleaner according to any one of [1] to [10].

[12] A permeable membrane cleaning solution comprising an aqueous solution having a pH of 10 or more containing a chloramine compound, a surfactant and an alkali agent.

[13] A cleaning solution for a permeable membrane according to [11] or [12], wherein the pH of the aqueous solution is 12 or more and 13 or less.

[14] In any one of [11] to [13], the concentration of the chloramine compound in the aqueous solution is 0.005 to 0.5M, and the concentration of the surfactant is 0.0001 to 0.05M. A permeable membrane cleaning solution.

[15] A method for cleaning a permeable membrane, comprising bringing the permeable membrane into contact with the permeable membrane cleaning liquid according to any one of [11] to [14].

  According to the present invention, a chlorine-based detergent component can be applied even to an aromatic polyamide-based RO membrane having low chlorine resistance. For this reason, in addition to the exfoliation effect and hydrolysis effect under alkaline conditions, sterilization and organic matter decomposition effects by chloramine compounds, as well as dispersion effects by surfactants, are added, and these effects act synergistically to achieve good alkali The performance of the permeable membrane such as the RO membrane can be effectively recovered by the cleaning effect.

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.

  The cleaning agent for a permeable membrane of the present invention comprises an aqueous solution having a pH of 13 or more containing a chloramine compound, a surfactant and an alkali agent. The cleaning liquid for the permeable membrane of the present invention comprises an aqueous solution having a pH of 10 or more obtained by diluting the cleaning agent. Hereinafter, the cleaning agent for a permeable membrane of the present invention and a cleaning solution obtained by diluting the same may be referred to as “chloramine compound / surfactant-containing alkaline aqueous solution”.

<Washing mechanism>
As the chloramine compound, an amino acid obtained by reacting hypochlorous acid (HOCl) with a compound having a primary amino group (XNH ₂ ) by the reaction shown in the following reaction formulas (1) and (2), A compound (XNHCl) in which the hydrogen atom of the group is substituted with a chlorine atom is preferred. Since this compound has a weak oxidizing action on the membrane, even an aromatic polyamide RO membrane with low chlorine resistance can be used as a cleaning agent.
XNH ₂ + HOCl⇔XNHCl + H ₂ O (1)
XNH ₂ + OCl ⁻ ⇔XNHCl + OH ⁻ (2)

  The present invention enables application of a chlorine-based cleaning agent to cleaning of a permeable membrane such as an RO membrane under alkaline conditions. In the present invention, the sterilization and organic substance decomposition action by the chloramine compound and the dispersing action by the surfactant are synergistically added to the organic substance peeling action and hydrolysis action by washing under alkaline conditions. For this reason, according to this invention, the effect of alkali cleaning can be improved and the performance of the contaminated permeable membrane can be recovered effectively.

<Permeation membrane>
In the present invention, when an RO membrane, particularly an aromatic polyamide RO membrane having a low chlorine resistance (including a nanofiltration (NF) membrane) is to be cleaned, the cleaning effect is effectively exhibited. However, the permeable membrane to be cleaned is not limited to an RO membrane such as an aromatic polyamide RO membrane, and the present invention can be applied to a UF membrane and an MF membrane, and the membrane material is not limited. Moreover, there is no restriction | limiting also in the form of a film | membrane etc., This invention is applied effectively for the washing | cleaning of the permeable membrane for water treatment in a wide field | area.

<Chloramine compound>
In the present invention, the chloramine compound used as the chlorine-based cleaning agent component is either a compound having a primary amino group, ammonia, or an ammonium salt (hereinafter referred to as “NH ₂ -based compound”), hypochlorous. It is preferable to produce by mixing chloric acid and / or hypochlorite. Examples of the compound having a primary amino group include aliphatic amines, aromatic amines, sulfamic acids, sulfanilic acids, sulfamoylbenzoic acids, and amino acids. Examples of ammonium salts include ammonium chloride and ammonium sulfate. These may be used alone or in combination of two or more. Of these NH ₂ compounds, sulfamic acid (NH ₂ SO ₂ OH) is preferable. When monochlororosulfamine is produced using sulfamic acid, it becomes a stable chloramine compound. Since sulfamic acid does not contain carbon, it does not increase the TOC value of the cleaning agent. By using sulfamic acid and an alkaline agent in combination, a very effective cleaning agent is obtained.

On the other hand, hypochlorite to be reacted with NH ₂ -based compounds includes alkali metal salts of hypochlorous acid such as sodium hypochlorite and alkaline earth metal salts of hypochlorous acid such as calcium hypochlorite. Etc. can be used. These may be used alone or in combination of two or more.

When an NH ₂ -based compound and hypochlorous acid and / or hypochlorite are mixed to produce a chloramine compound, the NH ₂ -based compound and hypochlorous acid and / or hypochlorite are hypochlorous acid. The Cl ₂ / N molar ratio, which is the molar ratio between the effective chlorine (Cl ₂ ) derived from chloric acid and / or hypochlorite and the nitrogen atom N derived from the NH ₂ compound, is 0.1 to 1. It is preferable to use the chloramine in view of the production efficiency and stability of chloramine.

If the Cl ₂ / N molar ratio is larger than the above upper limit, free chlorine may be generated. If the Cl ₂ / N molar ratio is smaller than the above lower limit, the production efficiency of chloramine is lowered with respect to the NH ₂ -based compound used.
In this case, the amount of hypochlorous acid and / or hypochlorite is the amount of chloramine compound in the chloramine compound / surfactant-containing alkaline aqueous solution.

<Alkaline agent>
The alkaline agent used in the cleaning agent of the present invention can maintain solubility in a chloramine compound / surfactant-containing alkaline aqueous solution, and uses alkali metal hydroxides such as sodium hydroxide and potassium hydroxide. be able to. These may be used alone or in combination of two or more.

<Surfactant>
As the surfactant used in the present invention, those having a molecular weight of 1000 or less are preferable from the viewpoint of cleaning effect. A surfactant having an excessively high molecular weight may not only provide a cleaning effect, but may contaminate the membrane.

  Surfactants include anionic surfactants such as alkyl benzene sulfonates such as sodium dodecylbenzene sulfonate, alkyl sulfates such as sodium lauryl sulfate, and nonionic interfaces such as polyalkylene glycol monoalkyl ethers such as diethylene glycol monomethyl ether. 1 type (s) or 2 or more types, such as an activator, can be used. Among these, an anionic surfactant is particularly preferable in terms of dispersion effect.

<PH / chloramine compound concentration / surfactant concentration>
The cleaning liquid of the present invention comprises a chloramine compound / surfactant-containing alkaline aqueous solution, and has a pH of 10 or more. If the pH of the cleaning liquid is less than 10, the permeation flux cannot be sufficiently recovered. The higher the pH of the cleaning liquid is, the better the cleaning effect is. However, when the pH is too high, the handling property as the cleaning liquid is deteriorated and the risk of deterioration of the permeable membrane such as the RO membrane is increased. The pH of the cleaning liquid is preferably 12 or more and 13 or less.

The concentration of the chloramine compound in the cleaning liquid comprising the chloramine compound / surfactant-containing alkaline aqueous solution is preferably 0.005 to 0.5M, and particularly preferably 0.01 to 0.2M. If the concentration of the chloramine compound in the cleaning liquid is too low, a sufficient cleaning effect cannot be obtained, and if it is too high, the permeable membrane such as the RO membrane may be deteriorated. A chloramine compound concentration of 0.005 to 0.5 M is a concentration corresponding to a total chlorine concentration of 355 to 35,500 mg-Cl ₂ / L. The total chlorine concentration can be measured by the DPD method specified in JIS K0400-33-10.1999.

Chloramine compounds are conventionally used as a slime control agent for permeable membranes. The chloramine compound as the slime control agent is usually used at a low concentration of about 0.05 to 50 mg-Cl ₂ / L as the total chlorine concentration. The pH at that time is less than 10. On the other hand, the cleaning liquid of the present invention contains the chloramine compound at a high concentration as described above, has a high alkalinity of pH 10 or higher, and has a high cleaning effect.

  Further, the surfactant concentration in the cleaning liquid of the present invention comprising a chloramine compound / surfactant-containing alkaline aqueous solution is preferably 0.0001 to 0.05M, particularly preferably 0.001 to 0.02M. preferable. If the surfactant concentration is too low, the dispersion effect by the surfactant and the effect of improving the cleaning action cannot be sufficiently obtained. If the surfactant concentration is too high, the association of the surfactant becomes rather strong and the cleaning effect may be lowered. .

  The cleaning agent of the present invention is preferably composed of an aqueous solution containing a chloramine compound, a surfactant, and an alkali agent at a pH of 13 or more, preferably a pH of 13 to 15, and the chloramine compound concentration in the aqueous solution is 0.2 to 2M. In particular, it is preferably 1 to 2M, the alkali agent concentration is 1 to 3M, and the surfactant concentration is 0.01 to 1M, particularly 0.03 to 0.3M. This cleaning agent is diluted with water (preferably pure water) when preparing the cleaning liquid of the present invention having the above-mentioned pH, chloramine compound and surfactant concentration.

<Manufacturing method of cleaning agent and cleaning liquid>
The cleaning agent of the present invention is prepared by adding and dissolving an NH ₂ -based compound such as sulfamic acid in the aqueous solution of the alkali agent described above, and adding hypochlorous acid and / or hypochlorous acid to the resulting NH ₂ -based compound aqueous solution. It can be prepared by adding salt and mixing. It is preferable that the amount of water in the aqueous solution of the alkali agent is 50 to 90% by weight. The surfactant may be added in any of the cleaning agent preparation steps, may be included in advance in the aqueous solution of the alkali agent, and hypochlorous acid in the NH ₂ -based compound aqueous solution. And / or may be added when hypochlorite is added, or may be added before or after the addition of hypochlorous acid and / or hypochlorite. Preferably, the surfactant is added after the addition of hypochlorous acid and / or hypochlorite.

A compound having a primary amino group such as sulfamic acid may be added in the form of a salt. Examples of the salt include those that are soluble in a chloramine compound / surfactant-containing alkaline aqueous solution, and sodium sulfamate, potassium sulfamate, ammonium sulfamate, and the like can be used. The NH ₂ -based compound is added so that the chloramine compound concentration in the cleaning agent of the present invention is the above concentration. Amount of NH ₂ compound, the content ratio of the alkaline agent and the NH ₂ compound is preferably set to 0.5 to 0.7 with N / alkali metal (molar ratio). The NH ₂ -based compound can be added in a powder state or in an aqueous solution state. When using a sulfamate as the NH ₂ -based compound, the amount of alkali metal contained in the sulfamate is added as an alkali. When an aqueous solution is used, the amount of water contained in the aqueous solution is added as the amount of water in the alkaline aqueous solution.

On the other hand, hypochlorous acid and / or hypochlorite is preferably added as an aqueous solution having an effective chlorine (Cl ₂ ) concentration of 5 to 20 wt%, preferably 10 to 15 wt%. Hypochlorous acid and / or hypochlorite is used so that the concentration of the chloramine compound in the cleaning agent of the present invention is the above concentration, and the NH ₂ -based compound and hypochlorous acid and / or hypochlorous acid. It is added so that the content ratio with the salt is the aforementioned Cl ₂ / N molar ratio. Thereby, there is no generation | occurrence | production of foaming and a chlorine odor, and the cleaning agent of this invention which consists of aqueous solution formulation excellent in reactivity, stability, handleability, a chlorine-free odor, etc. can be manufactured efficiently. Even in this case, it is preferable to gradually add and mix hypochlorous acid and / or hypochlorite.

  The cleaning liquid of the present invention is produced by diluting the thus-prepared cleaning agent of the present invention with water, preferably pure water, at a pH of 10 or more so as to have the above-mentioned preferred chloramine compound and surfactant concentrations. Is done. 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.

<Other cleaning ingredients>
To the cleaning agent or cleaning liquid used in the present invention, other cleaning component may be added as long as the cleaning effect is not impaired.
For example, other cleaning agents such as chelating agents such as EDTA (ethylenediaminetetraacetic acid), EGTA (ethyleneglycolbis (aminoethylether) tetraacetic acid), IDA (iminodiacetic acid), etc. in order to enhance the peeling effect of membrane contaminants One or more components may be added.

In addition, by using a polyol compound having a molecular weight of 1000 or less, preferably a molecular weight of 60 to 1000, the cleaning effect can be further enhanced by the permeation into the permeable membrane such as the RO membrane and the dissolution of the contaminant. Here, when the molecular weight of the polyol compound exceeds 1000, there is a possibility of contributing to permeable membrane contamination such as RO membrane. As the polyol compound having a molecular weight of 1000 or less, for example, ethylene glycol, propylene glycol, polyethylene glycol (degree of polymerization 2 to 22) and the like can be used. These polyol compounds may be used individually by 1 type, and 2 or more types may be mixed and used for them.
Such a polyol compound may be added to the cleaning agent or cleaning liquid of the present invention, or may be used by adding to the following alkaline aqueous solution or acid aqueous solution.

  In addition, before and after cleaning the permeable membrane according to the present invention, membrane cleaning with another cleaning liquid may be performed. The cleaning effect can be further enhanced by combining film cleaning with other cleaning liquids.

  Prior to washing with the chloramine compound / surfactant-containing alkaline aqueous solution, which is the cleaning liquid of the present invention, or after washing with the chloramine compound / surfactant-containing alkaline aqueous solution, washing with an alkaline aqueous solution not containing the chloramine compound / surfactant is performed. be able to. As the alkali agent of the alkaline aqueous solution, those described above as the alkaline agent of the chloramine compound / surfactant-containing alkaline aqueous solution can be used. The pH of the alkaline aqueous solution is preferably pH 10 or more, particularly pH 12 to 13 in terms of cleaning effect and handleability.

  Further, 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 hydrochloric acid, nitric acid, citric acid, and oxalic acid is used. it can. The pH of the acid aqueous solution is preferably pH 4 or less, particularly preferably pH 1 to 3, in terms of cleaning effect and handleability.

<Washing method>
As a method for cleaning the permeable membrane using the chloramine compound / surfactant-containing alkaline aqueous solution, which is the cleaning liquid of the present invention, the permeable membrane may be brought into contact with the chloramine compound / surfactant-containing alkaline aqueous solution, and the method is particularly limited. There is no. Usually, immersion cleaning is performed by introducing a chloramine compound / surfactant-containing alkaline aqueous solution to the raw water side of the permeable membrane module and allowing to stand. In this immersion cleaning, the pH of the chloramine compound / surfactant-containing alkaline aqueous solution in contact with the permeable membrane is 10 or more, preferably 12 to 13, and the chloramine compound concentration is 0.005 to 0.5 M, particularly 0.01 to. At 0.2M, the surfactant concentration is 0.0001-0.05M, especially 0.001-0.02M.

  When washing is performed using the aforementioned alkaline aqueous solution or acid aqueous solution before and after washing with the chloramine compound / surfactant-containing alkaline aqueous solution, the same immersion washing as described above is usually employed.

  There is no particular limitation on the immersion cleaning time with the chloramine compound / surfactant-containing alkaline aqueous solution or other cleaning liquid, and it is sufficient that the recovery rate of the target film performance is obtained, but it is usually about 2 to 24 hours. .

  When washing with a chloramine compound / surfactant-containing alkaline aqueous solution and washing with an alkaline aqueous solution and / or an aqueous acid solution are performed in combination, the washing procedure is not particularly limited. If the acid cleaning with the acid aqueous solution is performed before the cleaning with the chloramine compound / surfactant-containing alkaline aqueous solution, it is possible to reduce and remove metals that may cause a catalytic effect on chlorine. The alkali cleaning with the aqueous alkali solution may be performed before or after the cleaning with the chloramine compound / surfactant-containing alkaline aqueous solution. When the alkali cleaning with the aqueous alkali solution is performed after the cleaning with the chloramine compound / surfactant-containing alkaline aqueous solution, an additional cleaning effect without risk of film deterioration can be obtained.

  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 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 to a raw water chamber 1A below the flat membrane cell 2 in which the RO membrane of the sealed container 1 is set by a high-pressure pump 4. As shown in FIG. 2, 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 cell 2 is fixed via an O-ring 8. The flat membrane cell 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 cell 2 is stirred by rotating the stirring bar 5 with a stirrer 3. The RO membrane permeated water is taken out from the pipe 12 through the permeated water chamber 1B on the upper side of the flat membrane cell 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.

[Examples 1 and 2 and Comparative Examples 1 to 4]
The following cleaning tests were performed using the following cleaning solutions.

<Cleaning liquid>
Example 1: Aqueous pH 12 sodium hydroxide solution containing 0.02M monochlororosulphamic acid and 0.0043M sodium dodecylbenzenesulfonate Example 2: Hydroxylation pH 12 containing 0.02M monochlorosulfuramic acid and 0.0052M sodium lauryl sulfate Sodium aqueous solution Comparative example 1: pH 12 sodium hydroxide aqueous solution Comparative example 2: pH 43 sodium hydroxide aqueous solution containing 0.0043 M sodium dodecylbenzenesulfonate Comparative example 3: pH 12 sodium hydroxide aqueous solution containing 0.0052 M sodium lauryl sulfate Comparative Example 4: pH 12 sodium hydroxide aqueous solution containing 0.02M monochlororosulmic acid

<Cleaning test>
The aromatic polyamide RO membrane “ES20” manufactured by Nitto Denko Corporation was loaded into the flat membrane test apparatus shown in FIGS. 1 and 2 and the pure water permeation flux before contamination was measured under the conditions of 0.75 MPa and 25 ° C. . Thereafter, semi-clean KG containing nonionic surfactant (manufactured by Yokohama Oils & Fats Industry Co., Ltd.) was diluted 375 times, and water was passed for 72 hours under the conditions of 0.75 MPa and 25 ° C. to contaminate the RO membrane. After measuring the pure water permeation flux of the RO membrane after the contamination under the same conditions, each cleaning solution was supplied to fill the container with the cleaning solution and immersed for 17 hours for cleaning. After immersion cleaning, pure water was supplied and the cleaning liquid in the container was pushed out with pure water, and the pure water permeation flux of the RO membrane after cleaning was measured under the same conditions. The results are shown in Table 1.

  From Table 1, in Examples 1 and 2 using the cleaning liquid of the present invention comprising an aqueous alkali solution containing a chloramine compound and a surfactant, the permeation flux can be recovered to a state close to the permeation flux before contamination. I understand. In contrast, Comparative Example 1 using an aqueous alkali solution and Comparative Examples 2 and 3 using an aqueous alkali solution containing a surfactant have a low permeation flux recovery rate, and an alkaline aqueous solution containing a chloramine compound is used. In Comparative Example 4, the cleaning effect is superior to those of Comparative Examples 1 to 3, but in comparison with Comparative Example 4, Examples 1 and 2 in which a surfactant is used in combination provide a higher cleaning effect.

[Example 3, Comparative Examples 5 and 6]
The following cleaning tests were performed using the following cleaning solutions.

<Cleaning liquid>
Example 3 A pH of 12.3 prepared by diluting an aqueous solution containing 1 M sodium hypochlorite, 1.85 M sulfamic acid, 0.1 M sodium lauryl sulfate and 2.8 M sodium hydroxide to 2%. Comparative Example 5: Sodium hydroxide aqueous solution of pH 12.3 Comparative Example 6: A detergent comprising an aqueous solution containing 1 M sodium hypochlorite, 1.85 M sulfamic acid and 2.8 M sodium hydroxide was diluted to 2% PH 12.3 prepared aqueous solution

Since the cleaning agents of Example 3 and Comparative Example 6 above contain 1M sodium hypochlorite and 1.85M sulfamic acid, the Cl ₂ concentration is 1M, and the Cl ₂ / N molar ratio = 1 / 1.85 = 0.54.

<Cleaning test>
An aromatic polyamide RO membrane “ES20” manufactured by Nitto Denko Corporation was loaded into the RO membrane separation device in the wastewater collection system of the test laboratory and operated for six months. The RO membrane after operation was taken out from the RO membrane separator and disassembled to obtain a flat membrane sample. A flat membrane sample was cut into a circle and installed in the flat membrane test apparatus shown in FIGS. 1 and 2, and first, the pure water permeation flux before washing was measured under the conditions of 0.75 MPa and 25 ° C. Thereafter, each cleaning solution was supplied and immersion cleaning was performed for 17 hours in the same manner as in Example 1, and the pure water permeation flux after cleaning was measured under the same conditions. The results are shown in Table 2.

  As is clear from Table 2, Comparative Example 6 using an aqueous alkali solution containing a chloramine compound is superior in cleaning effect to Comparative Example 5 using an aqueous alkaline solution, but in Example 3 using a surfactant in combination, Excellent cleaning effect can be obtained at each stage.

DESCRIPTION OF SYMBOLS 1 Container 2 Flat membrane cell 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 (15)

  A cleaning agent for a permeable membrane comprising an aqueous solution having a pH of 13 or more containing a chloramine compound, a surfactant and an alkali agent.   The cleaning agent for a permeable membrane according to claim 1, wherein the pH of the aqueous solution is 13 or more and 15 or less.   In Claim 1 or 2, The density | concentration of the chloramine compound in the said aqueous solution is 0.2-2M, the density | concentration of surfactant is 0.01-1M, and the density | concentration of an alkaline agent is 1-3M, It is characterized by the above-mentioned. Permeable membrane cleaner.   The cleaning agent for a permeable membrane according to any one of claims 1 to 3, wherein the chloramine compound contains monochlororosulmic acid. 5. The chloramine compound according to claim 1, wherein the chloramine compound is selected from the group consisting of a compound having a primary amino group, ammonia and an ammonium salt (hereinafter referred to as “NH ₂ -based compound”). And a hypochlorous acid and / or hypochlorite. In claim 5, hypochlorous acid and / or hypochlorite and the NH ₂ -based compound, hypochlorous acid and / or hypochlorite-derived effective chlorine concentration (Cl ₂ ), A cleaning agent for a permeable membrane, which is mixed so that a molar ratio (Cl ₂ / N molar ratio) with a nitrogen atom N derived from the NH ₂ -based compound is 0.1 to 1. Mixture according to claim 5 or 6, and dissolved by addition of the NH ₂ compound in an aqueous solution of an alkaline agent, the NH ₂ compound aqueous solution obtained by adding hypochlorite and / or hypochlorite A permeable membrane cleaning agent obtained by the step of: 8. The aqueous solution of the alkali agent according to claim 7, wherein the amount of water is 50 to 90% by weight, and the ratio of the alkali agent to the NH ₂ -based compound is 0.5 to 0.00 in terms of N / alkali metal (molar ratio). 7. A permeable membrane characterized in that an NH ₂ -based compound is added so as to be 7, and hypochlorous acid and / or hypochlorite is added as an aqueous solution having an effective chlorine (Cl ₂ ) concentration of 5 to 20% by weight. Cleaning agent.   The permeable membrane cleaning agent according to any one of claims 1 to 8, wherein the surfactant is an anionic surfactant having a molecular weight of 1000 or less.   The cleaning agent for a permeable membrane according to claim 9, wherein the anionic surfactant is one or more selected from the group consisting of alkylbenzene sulfonate and alkyl sulfate.   A cleaning solution for a permeable membrane comprising an aqueous solution having a pH of 10 or more obtained by diluting the permeable membrane cleaner according to any one of claims 1 to 10.   A cleaning solution for a permeable membrane comprising an aqueous solution having a pH of 10 or more containing a chloramine compound, a surfactant and an alkali agent.   13. The permeable membrane cleaning solution according to claim 11, wherein the aqueous solution has a pH of 12 or more and 13 or less.   The chloramine compound concentration in the aqueous solution according to any one of claims 11 to 13 is 0.005-0.5M, and the surfactant concentration is 0.0001-0.05M. Permeation membrane cleaning solution.   A method for cleaning a permeable membrane, comprising bringing the permeable membrane into contact with the permeable membrane cleaning liquid according to any one of claims 11 to 14.

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