TW201710488A - Reverse osmosis membrane cleaning agent, cleaning liquid, and cleaning method - Google Patents

Abstract

Provided is a reverse osmosis membrane cleaning agent which effectively removes contaminants that cannot be sufficiently removed by conventional cleaning agents when a reverse osmosis (RO) membrane used to treat water, particularly an aromatic polyamide-based RO membrane, becomes contaminated, and the performance thereof in terms of the permeation flux, differential pressure, salt rejection rate, and the like is reduced. This reverse osmosis membrane cleaning agent includes a compound having an N-containing saturated heterocyclic ring. Also provided are: a cleaning liquid which includes said RO-membrane cleaning agent; and a method in which the cleaning agent or the cleaning liquid is used to clean an RO membrane. The compound having the N-containing saturated heterocyclic ring, and in particular a compound having, as a skeleton, a pyrrolidine ring, a pyrrolidone ring, an imidazolidine ring, or an imidazolidinone ring, exhibits an excellent cleaning effect with respect to contaminants adhered to an aromatic polyamide-based RO membrane.

Description

Detergent for reverse osmosis membrane, cleaning solution, and washing method

The present invention relates to a reverse osmosis (RO) membrane used in the field of water treatment, in particular, an aromatic polyamine-based RO membrane, which is effective in performance when the performance of a stream, differential pressure, and salt rejection is lowered. The RO membrane cleaning agent and the detergent to be recovered, and the cleaning method using the RO membrane.

As a countermeasure against the shortage of water supply in the world, the seawater and salt water using the RO membrane system are desalinated or drained. In the RO membrane system, the RO membrane is contaminated with various pollutants such as inorganic substances or organic substances. The degradation of the salt rejection rate, differential pressure, and permeation flux due to contamination of the RO membrane is a problem. Development of a cleaning technique that hopes to restore the performance of the contaminated RO membrane effectively.

As the RO membrane for water treatment, an aromatic polyamido-based RO membrane which is capable of low-pressure operation and has excellent desalination performance is widely used. The aromatic polyamine-based RO membrane has low resistance to chlorine, and cannot be treated in contact with chlorine under the operating conditions of the cellulose acetate-based RO membrane. The contamination by microorganisms or organic substances is greater than that of the cellulose acetate-based RO. Membrane is easier to send The problem of birth. The resistance to alkali is higher in the aromatic polyamine-based RO membrane than in the cellulose acetate-based RO membrane, and it can be washed under alkaline conditions of pH 10 or higher.

The alkaline-resistant aromatic polyamine RO membrane is a conventional detergent which is effective as a membrane fouling substance such as a microorganism or an organic substance, and the like (Non-Patent Document 1).

‧ alkaline agent (sodium hydroxide, etc.)

‧Interactive surfactant (sodium lauryl sulfate, etc.)

‧ Chelating agent (EDTA, etc.)

If the contamination of the RO membrane is severe, there is a case where the above-mentioned agent cannot be sufficiently washed.

For example, when an RO membrane is used in the treatment of raw water containing a large amount of inorganic substances or organic substances in a wastewater recovery system or a seawater desalination facility, a pollutant containing inorganic substances and organic substances adheres to the RO membrane. In the case of such a deposit, there is a case where the cleaning effect is insufficient by using the above-described cleaning agent. In particular, when a water supply of a polymer-containing polyalkylene glycol, a nonionic surfactant, a saccharide or a protein is treated with an RO membrane, the TOC component adheres to the membrane, and the performance of the membrane is gradually lowered. It is extremely difficult to restore the performance of the RO membrane by the above conventional cleaning agent.

Sodium hypochlorite is a potent agent for microorganisms or organic substances. Since the aromatic polyamine-based RO membrane has low resistance to chlorine, sodium hypochlorite is not used for washing the aromatic polyamide-based RO membrane. When a chlorine-based bactericide is known, the free chlorine is reduced by using a reducing agent, and then supplied to the RO membrane (Patent Document 1).

The pyrrolidone-based drug is used in the field of membrane separation technology, and is described as a solvent for a film, as described in Patent Document 3, and is used as a modifier. As described in Patent Document 4, it can also be used as a structural agent for a film.

The use of a pyrrolidone-based agent as a detergent component of the RO membrane has not been known so far.

Patent Literatures 5 to 7 disclose a technique of decomposing a sensitizer component remaining in a filter after filtering a photoresist by decomposition of N-methylpyrrolidone, but the object is not the object of washing as in the present invention. RO membrane contaminated with microorganisms or organic matter. The contaminated component of the RO membrane removed by the present invention is not decomposed and washed as the sensitizer component.

Patent Document 1: Japanese Laid-Open Patent Publication No. Hei 9-57067

Patent Document 2: Japanese Laid-Open Patent Publication No. 55-152507

Patent Document 3: Japanese Patent Laid-Open No. 7-171363

Patent Document 4: Japanese Patent Publication No. 2006-511330

Patent Document 5: Japanese Invention Patent No. 3832267

Patent Document 6: Japanese Invention Patent No. 3832268

Patent Document 7: Japanese Invention Patent No. 3832269

Non-Patent Document 1: "Self-degradation and fouling measures, membrane fouling prevention, cleaning method, and troubleshooting" (NTS issue) p142 2008

An object of the present invention is to provide an RO film for use in water treatment, in particular, an aromatic polyamine-based RO membrane, which is capable of effectively removing conventional filters when the performance of the flow beam, differential pressure, and salt rejection is lowered. The RO membrane cleaning agent and the cleaning solution for the pollutants which are not sufficiently removed by the detergent, and the cleaning method using the RO membrane.

The inventors of the present invention obtained various types of contaminated RO membranes, and conducted a thorough evaluation of effective detergent components, and found that a compound having a saturated heterocyclic ring containing N, particularly having a pyrrolidinium ring or a pyrrolidone ring, A compound having an imidazole ring and an imidazolinone ring as a skeleton imparts a high cleaning effect to a contaminant adhering to the aromatic polyamide-based RO film.

The present invention is based on the following.

[1] A detergent for reverse osmosis membrane comprising a compound having an N-containing saturated heterocyclic ring.

[2] The detergent for reverse osmosis membrane according to [1], wherein the N-containing saturated heterocyclic ring is selected from the group consisting of a pyrrolidine ring, a pyrrolidone ring, an imidazolidinium ring, an imidazolidinone ring, a piperidine ring, and a piperidine. ring.

[3] The detergent for reverse osmosis membrane according to [2], wherein the compound having an N-containing saturated heterocyclic ring is selected from pyrrolidine represented by the following formula (1) and a derivative thereof, and the following formula (2) One or more selected from the group consisting of imidazolium and its derivatives;

In the formula (1), R ₁ and R ₂ each independently represent a hydrogen atom or a hydrocarbon group having 1 to 4 carbon atoms which may have a substituent; and Q ₁ to Q ₄ each independently represent 2 hydrogen atoms, oxygen atoms, and hydrogen atoms. And any substituent or two arbitrary substituents.

[4] The detergent for reverse osmosis membrane according to any one of [1] to [3], which is used under alkaline conditions.

[5] The detergent for reverse osmosis membrane according to any one of [1] to [4] further comprising an anionic surfactant.

[6] The detergent for reverse osmosis membrane according to any one of [1] to [5] which further comprises a dispersing agent.

[7] A cleaning solution for a reverse osmosis membrane, comprising the detergent liquid for a reverse osmosis membrane according to any one of [1] to [6].

[8] The cleaning solution for reverse osmosis membrane according to [7], which is alkaline at pH 8 or higher.

[9] A method for cleaning a reverse osmosis membrane, which comprises the use of the reverse osmosis membrane cleaning agent according to any one of [1] to [6] or the reverse osmosis according to [7] or [8]. Membrane cleaning solution.

[10] The method for cleaning a reverse osmosis membrane according to [9], wherein The reverse osmosis membrane is an aromatic polyamine-based reverse osmosis membrane.

[11] The method for cleaning a reverse osmosis membrane according to [9] or [10], wherein the reverse osmosis membrane is used in seawater desalination or drainage treatment.

According to the present invention, when the RO membrane used for water treatment, in particular, the aromatic polyamine-based RO membrane is contaminated, and the performance of the flow beam, differential pressure, and salt rejection is lowered, the conventional cleaning can be effectively removed. Contaminants that cannot be adequately removed by the agent.

1‧‧‧ container

2‧‧ ‧ flat membrane unit

2A‧‧‧RO film

2B‧‧‧Porous support plate

3‧‧‧Agitator

4‧‧‧High pressure pump

5‧‧‧ stirrer

6‧‧‧ pressure gauge

7‧‧‧Pressure adjustment valve

8‧‧O ring

Fig. 1 is a model diagram showing the constitution of a flat film test apparatus used in the examples.

Fig. 2 is a cross-sectional view showing the structure of a hermetic container of the flat film test apparatus of Fig. 1.

Form of implementing the invention

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

[acting body]

Although the details of the mechanism of action of the present invention are not known, they are considered as follows.

By the peeling effect and hydrolysis effect under alkaline conditions other than washing Further, a compound having an N-containing saturated heterocyclic ring (hereinafter also referred to as "N-containing saturated heterocyclic compound") is imparted to the permeation of a contaminant, a hydrophilization effect, and an anionic interfacial activity when an anionic surfactant is used in combination. The effect of the agent on the penetration of the contaminant, the peeling effect, and the dispersion and chelating effect of the inorganic substance by the dispersing agent in the dispersing agent, and the synergistic action of these agents can improve the alkali washing effect.

Although the action mechanism of the N-saturated heterocyclic compound such as a pyrrolidine derivative or an imidazolium derivative for the cleaning effect is not known, it is judged that the saturated cyclic structure containing a nitrogen atom has a polyamine, particularly aromatic, with the RO membrane. Certain affinity of the polyamine surface to hydrophilize the contaminant.

[RO film]

In the present invention, the RO membrane to be washed may be a polyamine-based RO membrane such as an aromatic polyamine-based RO membrane, or may be a cellulose acetate-based RO membrane. The present invention is particularly effective for the washing of an aromatic polyamine-based RO membrane. The present invention is particularly effective for RO membranes, which are used for desalination or drainage treatment of seawater, and are contaminated with various types of pollutants, and it is not possible to obtain a sufficient cleaning effect with conventional detergents.

[RO film cleaning agent]

The RO film cleaning agent of the present invention is characterized by comprising an N-containing saturated heterocyclic compound. The cleaning agent for the RO film of the present invention is usually prepared by dissolving an N-containing saturated heterocyclic compound and an alkali agent or other chemicals which are optionally used in water.

In the present invention, the "cleaning agent" refers to a preparation for arranging and storing a product, and setting the concentration of the N-containing saturated heterocyclic compound or other agent higher than that at the time of use. "Washing solution" means a dilution of the detergent with water and adjustment to the concentration at which the film surface is actually washed.

<N-containing saturated heterocyclic compound>

The N-containing saturated heterocyclic ring which the N-containing saturated heterocyclic compound has is not particularly limited as long as it is a saturated heterocyclic ring having a nitrogen atom as a constituent atom of the ring. As the N-containing saturated heterocyclic ring, a 5-membered ring or a 6-membered ring is preferred, and a 5-membered ring is more preferred. Examples of the N-containing saturated heterocyclic ring include a 5-membered ring such as a pyrrolidine ring, a pyrrolidone ring, an imidazolidinium ring, and an imidazolidinone ring, a piperidine ring, and a piperidine. 6-member ring of the ring, etc.

The N-saturated heterocyclic compound is preferably pyrrolidine represented by the following formula (1), a derivative thereof, an imidazole represented by the following formula (2), and a derivative thereof, from the viewpoint of the cleaning effect thereof. Things. Formula (1) comprises a pyrrolidine ring and a pyrrolidone ring. Formula (2) contains an imidazolium ring and an imidazolinone ring.

In the formula (1), R ₁ and R ₂ each independently represent a hydrogen atom or a hydrocarbon group having 1 to 4 carbon atoms which may have a substituent; and Q ₁ to Q ₄ each independently represent 2 hydrogen atoms, oxygen atoms, and hydrogen atoms. And any substituent or two arbitrary substituents.

The "substituent" is a functional group or an atom other than a hydrogen atom, and a halogen atom is also contained in the substituent.

In the formulae (1) and (2), examples of the hydrocarbon group of R ₁ and R ₂ include an alkyl group, an alkenyl group, and an alkynyl group. The alkyl group may, for example, be a methyl group (-CH ₃ ) or an ethyl group (-CH ₂ CH ₃ ). The alkenyl group may, for example, be a vinyl group (-CH=CH ₂ ). Examples of the substituent which the hydrocarbon group may have include an aminocarbonyl group, a carboxyl group, an amine group, a hydroxyl group, and a halogen atom. For example, aminocarbonyl substituted on methyl group, a carbonyl group include a methyl group _{(-CH 2 C (O) NH} 2) and the like.

Examples of the substituent of any of Q ₁ to Q ₄ include a carboxyl group (-COOH), an amine group (-NH ₂ ), a hydroxyl group (-OH), and a halogen atom.

Specific examples of the N-containing saturated heterocyclic compound include the following compounds.

The N-containing saturated heterocyclic compound may be used singly or in combination of two or more.

<Other ingredients>

In addition to the N-containing saturated heterocyclic compound, the RO film-containing detergent of the present invention may contain an alkali agent, a cleaning agent, and a solvent other than the N-containing saturated heterocyclic compound which are necessary for the cleaning of the RO film.

The alkali agent used in the detergent for RO film of the present invention may, for example, be a hydroxide of an alkali metal such as sodium hydroxide or potassium hydroxide.

Examples of the solvent other than the N-containing saturated heterocyclic compound include alcohols such as ethanol, polyhydric alcohols such as ethylene glycol, propylene glycol, and butylene glycol, amines such as monoethanolamine, diethanolamine, and triethanolamine, and acetone. It An ether such as a ketone, dimethyl ether, diethyl ether or diethylene glycol monomethyl ether.

Examples of the detergent include a surfactant, a dispersant, and the like.

Examples of the surfactant include an anionic surfactant such as an alkylbenzenesulfonate such as sodium dodecylbenzenesulfonate or an alkylsulfate such as sodium dodecyl sulfate, such as diethylene glycol monomethyl. A nonionic surfactant such as a polyalkylene glycol monoalkyl ether such as a group ether.

Among these, an anionic surfactant is preferable especially in terms of a dispersion effect.

Examples of the dispersant include ethylenediaminetetraacetic acid (EDTA), glycol ether diamine tetraacetic acid (EGTA), polyphosphoric acid, phosphinium butane tricarboxylic acid (PBTC), phosphonic acid, polymaleic acid, A chelating agent such as citric acid, oxalic acid, gluconic acid, and the like.

These may be used alone or in combination of two or more.

The RO film cleaning agent of the present invention may be one dosage form in which a N-containing saturated heterocyclic compound, an alkali agent, a cleaning agent, or the like is mixed in advance, or one of these may be supplied as a separate drug. Or a dosage form of the above.

The cleaning solution for the RO membrane of the present invention prepared by diluting the detergent for RO membrane of the present invention with water may be one-dosage or two-dosage or more. In the case of a dosage form of two or more dosage forms, for example, after washing the RO membrane with a washing liquid containing a saturated heterocyclic compound containing N, It can be washed with a washing solution containing other washing agents.

When the detergent for the RO film of the present invention is diluted to about 5 to 100 times by weight with water or preferably pure water, the concentration of each of the chemicals suitable for the RO membrane cleaning solution of the present invention to be described later is The concentration of the drug in the RO membrane cleaning solution is adjusted to about 5 to 100 times by weight in order to prepare the respective drug concentrations.

The RO film cleaning agent of the present invention is prepared by preparing an aqueous solution or all or a part thereof as a powder or a solid.

[washing liquid]

The RO membrane cleaning solution of the present invention is an aqueous solution obtained by diluting the RO membrane cleaning agent of the present invention with water. In the RO membrane cleaning solution of the present invention, the RO membrane cleaning agent of the present invention may be diluted with water, and an alkali agent, a cleaning agent, another solvent, or the like may be added as needed to adjust the concentration to a predetermined concentration.

The RO film cleaning solution of the present invention can be directly prepared into a predetermined drug concentration without passing through the RO film detergent of the present invention.

The concentration of the N-containing saturated heterocyclic compound in the cleaning solution for the RO membrane of the present invention is also in accordance with the type of the N-containing saturated heterocyclic compound to be used, the pH of the cleaning solution, or the presence or absence of other cleaning agents, and the types thereof. It differs from the concentration and the like, but is preferably 0.1 to 10% by weight, particularly preferably about 0.5 to 5% by weight. When the concentration of the N-containing saturated heterocyclic compound is less than the above lower limit, the effect of cleaning the RO film by using the N-containing saturated heterocyclic compound cannot be sufficiently obtained. When the concentration of the N-containing saturated heterocyclic compound is higher than the above upper limit, there is also a decrease in the cleaning effect, and the nitrogen content of the washing waste liquid is not necessarily Want to rise.

The cleaning liquid for the RO film of the present invention has a pH of preferably 8 or more, particularly preferably 10 to 14, in terms of the cleaning effect.

If the pH of the cleaning liquid is less than 8, there is a case where the permeability of the film cannot be sufficiently recovered by washing. The higher the pH of the cleaning liquid, the more excellent the cleaning effect. However, if the pH is too high, the handleability of the cleaning liquid is deteriorated, and the risk of deterioration of the RO film is increased. The pH of the washing liquid is preferably 14 or less, more preferably 11 or more and 13 or less.

The RO membrane cleaning solution of the present invention is prepared by adding an alkali agent to prepare the above-mentioned suitable pH.

When the cleaning solution for the RO film of the present invention is applied to the washing of the cellulose acetate film, the pH can be adjusted to about 6 to 8 and used as a cleaning liquid in combination with the surfactant.

When the RO membrane cleaning solution of the present invention contains a surfactant, the concentration of the surfactant in the RO membrane cleaning solution of the present invention is preferably from 100 to 10,000 mg/L, particularly preferably from 300 to 5,000 mg/L. When the concentration of the surfactant in the cleaning solution for the RO film of the present invention is too low, the effect of improving the dispersion effect and the cleaning action by the surfactant cannot be sufficiently obtained. When the concentration of the surfactant in the cleaning solution for the RO film of the present invention is too high, the association of the surfactant becomes strong and the cleaning effect is lowered.

When the RO membrane cleaning solution of the present invention contains a dispersing agent, the concentration of the dispersing agent in the RO membrane cleaning solution of the present invention is preferably from 100 to 20,000 mg/L, particularly preferably from 1,000 to 10,000 mg/L. When the concentration of the dispersing agent in the cleaning solution for the RO membrane of the present invention is too low, the dispersing agent cannot be sufficiently obtained. Dispersion and washing effect. When the concentration of the dispersing agent in the cleaning liquid for RO membrane of the present invention is too high, the washing effect does not increase with respect to the concentration.

<Method for producing RO membrane cleaning agent and RO membrane cleaning solution>

The RO film cleaning agent of the present invention is prepared by mixing an N-containing saturated heterocyclic compound with an alkali agent, a cleaning agent, another solvent, or the like, if necessary. The RO film cleaning agent of the present invention can be prepared by using all or a part thereof as a powder or a solid.

In the cleaning solution for the RO membrane of the present invention, the RO membrane cleaning agent of the present invention produced as described above is diluted with water, preferably pure water, and an alkali agent, a cleaning agent, another solvent or the like is added as needed. The RO film cleaning solution of the present invention can also be produced in the same manner as described above without going through the RO film cleaning agent of the present invention.

<Washing method>

The method of washing the RO membrane using the RO membrane cleaning solution of the present invention is not particularly limited as long as the RO membrane is brought into contact with the cleaning solution. Usually, the washing liquid is introduced into the raw water side of the RO membrane module, and the immersion washing is carried out by standing. The cycle of washing the washing liquid may be performed before and/or after the immersion washing.

When the RO membrane cleaning agent and the RO membrane cleaning solution of the present invention are in the form of two or more dosage forms, they may be mixed and used for washing, or may be washed in order using respective agents. For example, after washing with a washing solution containing a saturated heterocyclic compound containing N, it is also possible to use other agents. Wash the washing solution.

After the cleaning of the RO membrane cleaning solution of the present invention is carried out, other washing is carried out, for example, when washing with an aqueous alkali solution or an aqueous acid solution, and generally, the same immersion washing or immersion as described above is employed. Wash and rinse.

In the washing of the cleaning liquid other than the cleaning solution for the RO film of the present invention, the cleaning solution for the RO film of the present invention can be washed with an aqueous alkali solution containing no saturated heterocyclic compound containing N. net. As the alkali agent for the aqueous alkali solution, the above-mentioned one which is used as an alkali agent in the cleaning solution for RO membrane of the present invention can be used. The pH of the aqueous alkali solution is preferably pH 10 or more, and particularly preferably pH 11 to 13, from the viewpoints of washing effect and workability.

In the washing of the washing liquid other than the cleaning liquid for RO film of the present invention, it is also possible to perform acid washing which is effective for removing dirt or metal colloid. In the acid washing, one or two or more kinds of aqueous solutions containing an acid such as hydrochloric acid, nitric acid, citric acid or oxalic acid can be used. The pH of the aqueous acid solution is preferably pH 4 or less, and particularly preferably pH 1 to 3, from the viewpoints of washing effect and workability.

The immersion washing time of the RO membrane cleaning solution and the other cleaning solution of the present invention is not particularly limited as long as the desired membrane performance recovery rate is obtained. The immersion washing time is usually about 2 to 24 hours. When the circulation washing is performed before the immersion washing, the circulation washing time is not particularly limited as long as the desired membrane performance recovery rate is obtained. The cycle cleaning time is usually about 0.5 to 3 hours.

Combining the cleaning of the RO membrane cleaning solution of the present invention with alkaline water dissolution When the liquid and/or the aqueous acid solution is washed, the washing procedure is not particularly limited. The acid washing of the aqueous acid solution is carried out before the washing of the RO membrane cleaning solution of the present invention, and is effective for removing the dirt component.

After the washing liquid is washed, high-purity water such as pure water is usually passed through and washed. Then, start the operation of the RO membrane system.

Example

The present invention will be more specifically described below by way of examples and comparative examples.

In the following examples and comparative examples, the cleaning effect of the RO film was examined using the flat film test apparatus shown in Figs.

In the flat membrane test apparatus, the RO membrane supply water is supplied from the pipe 11 to the raw water chamber 1A on the lower side of the flat membrane unit 2 on which the RO membrane is attached by the high pressure pump 4 . As shown in Fig. 2, the hermetic container 1 is composed of a lower case 1a on the raw water chamber 1A side and an upper case 1b on the side of the permeated water chamber 1B, between the lower case 1a and the upper case 1b, and the flat membrane unit 2 is interposed. The O-ring 8 is fixed. The flat membrane unit 2 is configured such that the permeated water side of the RO membrane 2A is supported by the porous support plate 2B. In the raw water chamber 1A on the lower side of the flat membrane unit 2, the agitator 5 is rotated by the agitator 3 to be stirred. The RO film is taken out from the pipe 12 through the permeated water chamber 1B on the upper side of the flat membrane unit 2 through the water. 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 regulating valve 7 provided in the concentrated water take-out pipe 13.

The washing test was carried out at 25 °C.

The permeation flux and the salt rejection ratio of the RO film were each calculated by the following formula.

Through the stream [m ³ /(m ² ‧day)] = permeate water flow [m ³ /day] / membrane area [m ² ] × temperature conversion factor [-]

Desalination rate [%] = (1 - Permeate water conductivity [mS / m] / Concentrated water conductivity [mS / m]) × 100

[Example I-1, Comparative Example I-1~4]

The washing test shown below was carried out using the following washing liquid.

<washing liquid>

Example 1: 1% by weight of N-methyl-2-pyrrolidone, 1500 mg/L of sodium dodecyl sulfate and 5000 mg/L of sodium gluconate, pH 12 aqueous sodium hydroxide solution

Comparative Example I-1: Aqueous sodium hydroxide solution at pH 12

Comparative Example I-2: sodium hydroxide solution containing 1% by weight of propylene glycol, 1500 mg/L of sodium dodecyl sulfate and 5000 mg/L of sodium gluconate, pH 12

Comparative Example I-3: sodium hydroxide solution containing 1% by weight of ethanol, 1500 mg/L of sodium dodecyl sulfate and 5000 mg/L of sodium gluconate, pH 12

Comparative Example I-4: 1% by weight of diethylene glycol monomethyl ether, 1500 mg/L of sodium dodecyl sulfate and 5000 mg/L of sodium gluconate, pH 12 aqueous sodium hydroxide solution

<Test method>

The aromatic polyamido-based RO membrane "TM-820A" (new membrane, through the stream 0.6 [m ³ /(m ² ‧day)]) of Toray Co., Ltd. was loaded into the RO device of the seawater desalination RO system. It has been in operation for 3 years. The film after the operation was taken out from the RO device and disassembled, and a flat film sample of the contaminated film was obtained. The flat film sample was cut in a circular shape and placed in a flat film test apparatus shown in Figs. 1 and 2 which can be loaded with the film of the same size, and tested by the following procedure.

(1) The pure water was passed through the contaminated film before washing at 1.55 MPa to obtain a permeated stream of pure water of the contaminated film before washing. Next, 2000 mg/L of an aqueous sodium chloride solution was passed under the same conditions to obtain a salt rejection ratio.

(2) Then, each washing liquid is supplied and washed. The washing operation was carried out in the order of 2 hours of circulation washing, 15 hours of immersion washing, and 2 hours of circulating washing. The operating pressure at the time of circulation washing was set to 0.2 MPa.

(3) Then, in the same manner as in the above (1), the permeated flux and the salt rejection ratio of the purified pure water were determined.

(4) The recovery rate was calculated by the following formula.

Recovery rate [-] = (permeate flow after washing) / (transmission beam of new film)

The results are shown in Table 1. In the table, "DEGME" means diethylene glycol monomethyl ether, "SDS" means sodium dodecyl sulfate, and "GANa" means sodium gluconate.

As is clear from Table 1, in the washing liquid using N-methyl-pyrrolidone in the solvent, the washing effect was superior to that of the other solvent system.

In Example I-1 and Comparative Examples I-1 to 4, the salt rejection ratio of the RO membrane after washing was almost the same as that of the RO membrane before washing, and was about 98 to 99%.

[Examples II-1-10, Comparative Examples II-1~9]

The washing test shown below was carried out using the following washing liquid.

<washing liquid>

Example II-1: Aqueous sodium hydroxide solution containing 2% by weight of N-methyl-2-pyrrolidone and 1500 mg/L of sodium dodecylbenzenesulfonate, pH 12.

Example II-2: Aqueous sodium hydroxide solution containing 2% by weight of 2-pyrrolidone and 1500 mg/L of sodium dodecylbenzenesulfonate, pH 12.

Example II-3: Aqueous sodium hydroxide solution containing 2% by weight of 1-ethyl-2-pyrrolidone and 1500 mg/L of sodium dodecylbenzenesulfonate, pH 12.

Example II-4: Aqueous sodium hydroxide solution containing 2% by weight of pyrrolidine and 1500 mg/L of sodium dodecylbenzenesulfonate, pH 12.

Example II-5: Aqueous sodium hydroxide solution containing 2% by weight of L-pyroglutamic acid and 1500 mg/L of sodium dodecylbenzenesulfonate, pH 12.

Example II-6: Aqueous sodium hydroxide solution containing 2% by weight of 2-imidazolidinone and 1500 mg/L of sodium dodecylbenzenesulfonate, pH 12.

Example II-7: Aqueous sodium hydroxide solution containing 2% by weight of 2-oxo-1-pyrrolidone acetamide and 1500 mg/L of sodium dodecylbenzenesulfonate, pH 12.

Example II-8: Aqueous sodium hydroxide solution containing 2% by weight of N-methyl-2-pyrrolidone and pH 12

Example II-9: Aqueous sodium hydroxide solution containing 2% by weight of pyrrolidine and pH 12

Example II-10: Aqueous sodium hydroxide solution containing 2% by weight of piperidine and pH 12

Comparative Example II-1: Aqueous sodium hydroxide solution at pH 12

Comparative Example II-2: Sodium hydroxide aqueous solution containing 1500 mg/L sodium dodecylbenzenesulfonate and pH 12

Comparative Example II-3: Aqueous sodium hydroxide solution containing 2% by weight of propylene glycol and 1500 mg/L of sodium dodecylbenzenesulfonate, pH 12.

Comparative Example II-4: Aqueous sodium hydroxide solution containing 2% by weight of ethylene glycol and 1500 mg/L of sodium dodecylbenzenesulfonate, pH 12.

Comparative Example II-5: comprising 2% by weight of diethylene glycol monomethyl ether and 1500mg/L sodium dodecylbenzene sulfonate, pH 12 sodium hydroxide solution

Comparative Example II-6: Aqueous sodium hydroxide solution containing 2% by weight of monoethanolamine and 1500 mg/L of sodium dodecylbenzenesulfonate, pH 12.

Comparative Example II-7: Aqueous sodium hydroxide solution containing 2% by weight of ethanol and pH 12

Comparative Example II-8: Aqueous sodium hydroxide solution containing 2% by weight of acetone and pH 12

Comparative Example II-9: Aqueous sodium hydroxide solution containing 2% by weight of propylene glycol and pH 12

<Test method>

An aromatic polyamine-based RO film "ES-20" (new film) manufactured by Nitto Denko Corporation was cut into a flat flat film and placed in a flat film test apparatus shown in Figs. 1 and 2 which can be filled with the same size film. The washing test was carried out using the following procedure.

(1) Pure water was passed through the new membrane at 0.75 MPa for 24 hours, and the pure water of the new membrane was passed through the stream. Next, a 500 mg/L sodium chloride aqueous solution was passed under the same conditions to obtain a salt rejection ratio.

(2) Next, an aqueous solution containing a nonionic surfactant (200 mg/L SemiClean KG (Yokohama Oil Industry) aqueous solution) was passed at 0.75 MPa for 3 days to form a contaminated film. With respect to this contaminated film, the permeate flux and the salt rejection ratio of pure water were determined in the same manner as in the above (1).

(3) Then, each of the washing liquids is supplied and washed. Washing operation is washed according to 2 hours of circulation → 15 hours of immersion washing → 2 hours of circulation The order of washing is carried out. The operating pressure at the time of circulation washing was set to 0.2 MPa.

(4) Then, in the same manner as in the above (1), the permeate flux of pure water and the salt rejection ratio were determined.

(5) The recovery rate was calculated by the following formula.

Recovery rate [-] = (permeate flow after washing) / (transmission beam of new film)

The results are shown in Table 2. In the table, "DEGME" means diethylene glycol monomethyl ether, and "SDBS" means sodium dodecylbenzenesulfonate.

As is apparent from Table 2, in Examples II-1 to II-10, in Examples II-1 to II-7 in which an anionic surfactant was used in combination, the recovery ratio was 0.85 or more, even without an anionic interface. In Examples II-8 to II-10 of the active agent, it was also shown that the cleaning effect was superior to Comparative Example II-7 using no anionic surfactant or Comparative Example II-2 using an anionic surfactant. . Compared with Comparative Example II-6, a high cleaning effect was also obtained without anionic surfactant.

In particular, the washing liquid using pyrrolidine, 1-ethyl-2-pyrrolidone, or N-methyl-2-pyrrolidone has a high washing effect.

As a result of the above, it was found that by using a compound containing an N-containing saturated heterocyclic ring having a pyrrolidine ring, a pyrrolidone ring, an imidazolidinium ring, an imidazolidinone ring or the like, a specific solvent (propylene glycol, diethylene glycol) was obtained. , monoethanolamine, etc.) washing solution has a higher washing effect.

The salt rejection rates of the new membranes, the contaminated and the washed RO membranes of Examples II-1 to II-10 and Comparative Examples II-1 to II-9 were almost the same, ranging from 97 to 99%, and it was confirmed that the salt rejection rate was almost impossible. The cleaning of the invention is reduced.

The present invention has been described in detail with reference to the specific embodiments thereof, and it is understood that various modifications are possible without departing from the spirit and scope of the invention.

The present application is based on Japanese Patent Application No. 2015-147778 filed on Jul. 27, 2015, the entire disclosure of which is incorporated herein by reference.

1‧‧‧ container

1A‧‧‧ Raw Water Room

1B‧‧‧through water room

2‧‧ ‧ flat membrane unit

3‧‧‧Agitator

4‧‧‧High pressure pump

5‧‧‧ stirrer

6‧‧‧ pressure gauge

7‧‧‧Pressure adjustment valve

11‧‧‧Pipe

12‧‧‧Pipe

13‧‧‧Concentrated water take-out pipe

Claims (11)

A detergent for reverse osmosis membrane comprising a compound having an N-containing saturated heterocyclic ring. The detergent for reverse osmosis membrane according to claim 1, wherein the aforementioned N-containing saturated heterocyclic ring is selected from the group consisting of a pyrrolidine ring, a pyrrolidone ring, an imidazolidinium ring, an imidazolidinone ring, a piperidine ring, and a piperidine. ring. The detergent for reverse osmosis membrane according to claim 2, wherein the compound having an N-containing saturated heterocyclic ring is selected from pyrrolidine represented by the following formula (1) and a derivative thereof and an imidazole represented by the following formula (2) One or more selected from the group consisting of pyridine and its derivatives; In the formula (1), R ₁ and R ₂ each independently represent a hydrogen atom or a hydrocarbon group having 1 to 4 carbon atoms which may have a substituent; and Q ₁ to Q ₄ each independently represent 2 hydrogen atoms, oxygen atoms, and hydrogen atoms. And any substituent or two arbitrary substituents. The detergent for reverse osmosis membrane according to any one of claims 1 to 3, which is used under alkaline conditions. The detergent for reverse osmosis membrane according to any one of claims 1 to 4, which further comprises an anionic surfactant. The detergent for reverse osmosis membrane according to any one of claims 1 to 5, which further comprises a dispersing agent. A cleaning solution for a reverse osmosis membrane comprising the detergent for reverse osmosis membrane according to any one of claims 1 to 6. The cleaning solution for reverse osmosis membrane according to claim 7, which is alkaline at pH 8 or higher. A method of cleaning a reverse osmosis membrane, which comprises the use of a detergent for reverse osmosis membrane according to any one of claims 1 to 6 or a cleaning solution for reverse osmosis membrane according to claim 7 or 8. The method of cleaning a reverse osmosis membrane according to claim 9, wherein the reverse osmosis membrane is an aromatic polyamine-based reverse osmosis membrane. A method of cleaning a reverse osmosis membrane according to claim 9 or 10, wherein the reverse osmosis membrane is used in seawater desalination or drainage treatment.