JPH11104470A - Regeneration of reverse osmosis membrane and reverse osmosis membrane module - Google Patents

Abstract

PROBLEM TO BE SOLVED: To retreat a reverse osmosis membrane element under a module condition as it is by preparing an org. solvent contg. a reactive polyfunctional acid halide and/or a polyfunctional isocyanate or both of them and introducing this soln. into a reverse osmosis membrane module to bring it into contact with the skin layer of the membrane surface. SOLUTION: When a reverse osmosis membrane element whose performance is lowered, caused by deterioration of the membrane, is regenerated, at first, the element is washed to remove contaminant of the membrane. After washing is finished,'v'water soln. contg. a detergent is removed and water in the element is drip-dried. Then, an org. solvent soln. contg. a polyfunctional halide or a polyfunctional isocyanate are independently, successively or under a mixed condition fed from a treating liq. feeding side for the element to perform repair of the membrane. Namely, parts of amino groups are crosslinked again under an element condition as it is to perform repair. As the polyfunctional halide used, arom. acid chlorides, etc., are pref. and as the polyfunctional isocyanate, tolylene diisocyanate, etc., are cited.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for regenerating a reverse osmosis membrane element whose performance has deteriorated due to membrane deterioration. By using the regeneration method of the present invention, it is possible to regenerate and reuse a reverse osmosis membrane element which has been conventionally discarded due to deterioration in performance due to membrane deterioration.

[0002]

2. Description of the Related Art At present, a typical reverse osmosis membrane industrially used is an asymmetric membrane made of cellulose acetate. Such a reverse osmosis membrane is disclosed, for example, in US Pat. No. 3,133,132.
U.S. Pat. No. 3,133,137 discloses a Rob type reverse osmosis membrane. Also, reverse osmosis membranes having different structures from this are known, such as reverse osmosis composite membranes in which an active thin film having substantially selective separation is provided on a microporous support membrane. Current,
As a widely used reverse osmosis composite membrane, there is a reverse osmosis composite membrane formed on a support membrane of a thin film made of a polyamide obtained by interfacial polymerization of a polyfunctional aromatic amine and a polyfunctional aromatic acid halide (for example, JP-A-55-147106, JP-A-55-147106
62-121603, JP-A-63-218208, JP-A-2-187135, etc.). Further, there is also known a thin film formed of a polyamide obtained by interfacial polymerization of a polyfunctional aromatic amine and a polyfunctional alicyclic acid halide on a support film (for example, JP-A-61-42308 and the like). ). These reverse osmosis membranes are elemented in a form such as a spiral shape and incorporated in a module.

[0003] When the use of these various reverse osmosis membrane elements causes membrane contamination, they are repeatedly washed to remove them. The membrane of the reverse osmosis membrane element gradually deteriorates (reduction of blocking performance, increase (or decrease) of permeated water) due to such a washing operation, and finally can maintain the intended performance specification range. And it will be replaced with a new element. In order to reduce the blocking performance of the reverse osmosis membrane, various water-soluble polymer solutions are added as a blocking performance recovery agent during operation, but this is not a fundamental regeneration method. In recent years, social demands for reducing the burden on the environment, such as the reduction of industrial waste, have been extremely large, and there is a strong demand for an effective regeneration method for used reverse osmosis membrane elements.

[0004]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a method for treating a reverse osmosis membrane element which has been discarded as a non-reproducible membrane element in a module state and has been regenerated into a usable element again. And to provide a reverse osmosis membrane module incorporating the element thus regenerated.

[0005]

According to a first aspect of the present invention, there is provided a reactive polyfunctional acid halide and / or polyfunctional isocyanate,
Alternatively, there is provided a method for regenerating a membrane-degraded reverse osmosis membrane element, which comprises preparing an organic solvent containing both of them, introducing the solution into a reverse osmosis membrane module, and bringing the solution into contact with a skin layer on the reverse osmosis membrane surface. Is what you do.

The second invention of the present application is characterized in that a water-insoluble organic polymer compound solution is prepared at 25 ° C., and the solution is introduced into a reverse osmosis membrane module and brought into contact with a skin layer on the surface of the reverse osmosis membrane. The present invention provides a method for regenerating a reverse osmosis membrane element having deteriorated membrane.

Further, the present application is a third aspect of the present invention, wherein
Another object of the present invention is to provide a method for treating a reverse osmosis membrane treated according to the invention of the second aspect with a water-insoluble organic polymer compound solution by the method of the second aspect.

Further, the present invention provides a reverse osmosis membrane module incorporating a reverse osmosis membrane element regenerated by these methods.

According to such a method for regenerating a reverse osmosis composite membrane element, it has been possible to regenerate a discarded element whose performance has been deteriorated due to membrane degradation and reuse it.

According to the regeneration method of the present invention, various reverse osmosis membranes and reverse osmosis composite membranes of polyamide, polyurea, etc.
Particularly, a film formed by the interfacial polymerization method can be regenerated. These films may be obtained by a conventionally known method or the like. For example, an aqueous solution of a monomer and / or a polymer having a reactive amino group such as metaphenylenediamine, piperazine, and polyethyleneimine is used.
After coating on at least one surface such as a porous polysulfone support membrane, it is brought into contact with a solvent such as trimesic acid chloride, a polyfunctional acid chloride such as isophthalic chloride, or a polyfunctional isocyanate such as tolylene diisocyanate, or a mixture thereof such as hexane. Alternatively, a reverse osmosis composite membrane can be formed by performing interfacial polymerization on the support membrane to form a film having desalination performance.

[Membrane Washing] In order to regenerate an element whose performance has been reduced by using these reverse osmosis composite membranes, it is preferable to first wash the element and remove as much membrane contaminants as possible. Although the cleaning agent and the cleaning method used here are not particularly limited, for example, it is preferable to use an aqueous solution of sodium hydroxide solution, sodium hypochlorite solution, oxalic acid, citric acid, or the like. The cleaning agent concentration of these cleaning solutions is 0.1.
It is 001 to 30% by weight, preferably 0.01 to 5% by weight.

After the cleaning is completed, the aqueous solution containing the cleaning agent is sufficiently removed, and the water in the element is drained. As such a draining method, it is efficient to introduce dry air from the supply side of the element, but it is not particularly limited. Further, at this time, it is preferable that the element is not completely dried in order to suppress a decrease in water permeability of the element after regeneration.

[Repair of Film] (1) In the first invention of the present application, an organic solvent solution (repair liquid) containing a polyfunctional acid halide and a polyfunctional isocyanate is supplied from the treatment liquid supply side of the element subjected to the cleaning treatment as described above. The film is supplied alone, sequentially, or in combination to repair the film. In this method, the amino group generated by the film deterioration is cross-linked and repaired again in the element state.

Examples of such polyfunctional acid halides used for repairing the membrane include aromatic acid chlorides such as trimesic acid chloride and isophthalic acid chloride, aliphatic acid chlorides such as butanetetracarboxylic acid chloride, and the like.
Preferred are alicyclic acid chlorides such as 1,2,3,4-cyclopentanetetracarboxylic acid chloride and 1,3,4-cyclopentanetricarboxylic acid chloride.

Preferred examples of the polyfunctional isocyanate include, for example, tolylene diisocyanate, 4,4 ′
-Diphenylmethane diisocyanate, p-phenylene diisocyanate and the like. These may be used alone or as a mixture of two or more.

The concentration of the polyfunctional halide and polyfunctional isocyanate in the solution is 0.001 to 1.0% by weight, preferably 0.01 to 0.5% by weight. If the concentration is lower than this range, the crosslinking reaction does not sufficiently occur, and the membrane is not repaired sufficiently. On the other hand, if the concentration is higher, the water permeability after the repair is largely reduced.

As a solvent for the repairing solution, any solvent can be used as long as it can dissolve a polyfunctional acid halide and a polyfunctional isocyanate. For example, a hydrophobic organic solvent such as heptane, hexane and pentane is preferably used. In the solvent, ethanol and isomer are added to improve the affinity of the hydrophobic solution on the membrane surface.
Alcohols such as o-propanol, ethers such as diethylene glycol dimethyl ether, N-methylpyrrolidone, dimethylformamide and the like may be incorporated in the solution in an amount of 0.01 to 50% by weight.

Various methods may be used for supplying the repair liquid to the module. For example, the repair liquid can be quantitatively poured using a pump or the like. The contact time between the reverse osmosis membrane surface and the repair liquid is preferably about 1 second to 1 minute. After the treatment with the repair solution, the reverse osmosis membrane is dried. An appropriate method may be used for drying. For example, it is efficient to introduce dry air from the supply side of the element. The drying temperature is 20 to 150 ° C, preferably 25 to 100 ° C in order to maintain the moisture retention of the film.

(2) In the second invention of the present application, an organic polymer solution (repair solution) that is water-insoluble at 25 ° C. is prepared on the reverse osmosis membrane prepared by washing and removing membrane contaminants in the same manner as in the first invention. Is brought into contact with the skin layer on the surface of the reverse osmosis membrane of the module, and the defective portion of the element whose membrane has deteriorated is covered with an organic polymer compound.

The organic polymer compound used in the organic polymer solution for repair is not particularly limited, and examples thereof include an organic polymer having an -OH group such as polyvinyl alcohol and ethylene-vinyl alcohol copolymer, and sulfonated polysulfone. organic polymer having a -SO ₃ H group as, and an organic polymer having a -NH ₂ group, such as polyethyleneimine. Of these, polyvinyl alcohol and ethylene vinyl alcohol copolymer are particularly preferred.

The concentration of the organic polymer compound in the solution is 0.1
It is from 0.01 to 20% by weight, preferably from 0.05 to 5% by weight. If the concentration of the organic polymer compound is lower than this, the coating cannot be performed sufficiently and the restoration is insufficient. On the other hand, if the concentration is higher than this, the amount of permeated water is greatly reduced.

Examples of the solvent used in the repairing solution include water, a lower alcohol, a halogenated hydrocarbon, an aliphatic hydrocarbon, acetone, and acetonitrile, which are solvents that hardly damage the active film layer of the reverse osmosis composite membrane. as well as,
It is preferable to use a mixed solution of these. The repair fluid includes
Further, aliphatic alcohols such as methanol, ethanol, propanol and butanol, halogenated aliphatic alcohols such as ethylene chlorohydrin, methoxymethanol and methoxyethanol may be mixed. In particular, one or more of these lower alcohols and water and It is preferable to use a mixed solvent of When a mixed solvent of water and a lower alcohol is used, the water content is preferably 90% or less. When water is used as the solvent, a surfactant may be added to improve the wettability with the film.

The treatment of the element with such a repair liquid is performed, for example, by introducing the solution from the supply side of the element. For example, a method of quantitatively pouring using a pump or the like is preferable. The element treated with the solution is dried by an appropriate method. For example, it is efficient and preferable to introduce dry air from the supply side of the element. The drying temperature is 20-150 ° C, 25-10
The temperature is preferably 0 ° C. in order to maintain the moisture retention of the film.

These are preferably crosslinked to completely insolubilize in water. Crosslinking may occur simultaneously with the repair treatment, after the repair, or both.

The crosslinking method is not particularly limited, but a thermal crosslinking method or a chemical crosslinking method is used. The chemical crosslinking method can be carried out by immersion in a polyhydric aldehyde solution under a hydrochloric acid solution. Glutaraldehyde, glyoxal, terephthalaldehyde, and the like are used as the polyhydric aldehyde. In addition, an epoxy compound, a polycarboxylic acid, and a polycarboxylic acid halide can be used.

The thickness of the thin film of the polymer compound thus provided on the reverse osmosis composite membrane is 0.001-1 μm,
Preferably, the thickness is about 0.005 to 0.5 μm in order to suppress a decrease in water permeability due to coating. An appropriate method may be used to control the film thickness, but it is convenient to adjust the film concentration by adjusting the solution concentration.

Further, the present invention relates to a reverse osmosis membrane which has been treated with an organic solvent solution containing a polyfunctional acid halide and a polyfunctional isocyanate according to the first aspect of the present invention, and a water-insoluble organic polymer having a high water-insoluble property. A method for regenerating an element that is brought into contact with a molecular compound solution may be employed.

[0028]

Next, the present invention will be described in more detail with reference to examples.

Example 1 The following experiment was performed using an ES10-D4 element (manufactured by Nitto Denko Corporation). First, the element was sufficiently washed using an aqueous solution of sodium hypochlorite (200 ppm). After washing, this element was measured to find the initial performance: sodium chloride (NaCl) rejection: 9
9.5%, permeated water amount: 30 (m ³ / d) (NaCl solution concentration: 5
00 ppm, pressure: 7.5 kgf / cm ² )
Due to membrane deterioration, NaCl rejection: 98.5%, permeated water amount: 3
The performance was reduced to 7 (m ³ / d). After washing this element with water, dry air was blown onto the membrane surface from the supply side to remove excess water on the membrane surface.

Then, trimesic acid chloride 0.25
A weight% hexane solution was introduced from the supply side of the element and brought into contact with the skin layer. After 20 seconds, the liquid was drained, and dried by blowing dry air (temperature: 80 ° C.) from the supply side.
When the performance of the element was evaluated again, the NaCl rejection:
The water content was 99.2% and the permeated water amount was 26 (m ³ / d), and the regeneration of the performance of the element was confirmed.

Example 2 A reverse osmosis membrane was regenerated by treating in the same manner as in Example 1 except that a hexane solution containing 0.5% by weight of tolylene diisocyanate was used instead of trimesic acid chloride. When the performance of this element was evaluated again, the NaCl rejection was 99.0% and the permeated water amount was 20 (m ³ / d), and regeneration of the element performance was confirmed.

Example 3 In the same manner as in Example 1, regeneration was performed using an element treated with 200 ppm of sodium hypochlorite solution. That is, polyvinyl alcohol
(Saponification degree: 99%) was converted to isopropyl alcohol / water = 3 /
7 to prepare a 0.10% by weight solution. This solution was introduced from the supply side of the element and brought into contact with the skin layer for 10 seconds. After draining, dry air (temperature: 80
° C) from the supply side and dried. When the performance of this element was evaluated again, the NaCl rejection rate was 99.0% and the permeated water amount was 20 (m ³ / d).

Example 4 The element regenerated in Example 1 was further treated in the same manner as in Example 3 with polyvinyl alcohol (degree of saponification: 99%). When the performance of this element was evaluated again, the NaCl rejection was 99.5% and the amount of permeated water was 21 (m ³ / d), and regeneration of the element performance was confirmed.

[0034]

According to the method for regenerating a reverse osmosis composite membrane element of the present invention, an element which has been conventionally discarded due to membrane deterioration can be regenerated and reused.

Claims (5)

[Claims] An organic solvent containing a reactive polyfunctional acid halide and / or a polyfunctional isocyanate is prepared, and the solution is introduced into a reverse osmosis membrane module to be brought into contact with a skin layer on the reverse osmosis membrane surface. Of a reverse osmosis membrane element with deteriorated membrane. 2. A reverse-degraded reverse membrane comprising preparing a water-insoluble organic polymer compound solution at 25 ° C., introducing the solution into a reverse osmosis membrane module, and bringing the solution into contact with a skin layer on the reverse osmosis membrane surface. A method for regenerating a permeable membrane element. 3. A water-insoluble organic polymer compound solution is brought into contact with a skin layer on the reverse osmosis membrane surface of a reverse osmosis membrane module treated with an organic solvent containing a reactive polyfunctional acid halide and / or polyfunctional isocyanate. Item 2. A method for regenerating a reverse osmosis membrane element according to Item 2. 4. A reverse osmosis membrane module incorporating a reverse osmosis membrane element regenerated by bringing an organic solvent containing a reactive polyfunctional acid halide and / or polyfunctional isocyanate into contact with a skin layer. 5. A reverse osmosis membrane module incorporating a reverse osmosis membrane element regenerated by bringing a water-insoluble organic polymer compound solution into contact with a skin layer at 25 ° C.