JPH11169689A - Method for evaluating performance of composite reverse osmosis membrane and treatment of liquid using same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To precisely evaluate a composite reverse osmosis membrane having a high salt blocking rate in a short time by measuring the life of orthopositronium in a polyamide resin in the dry state in the membrane by a positron life measuring method. SOLUTION: A skin layer of a polyamide resin formed by the interfacial reaction of a compd. having two or more reactive amino groups with a multifunctional acid halide is disposed on a porous substrate to obtain a composite reverse osmosis membrane. In order to evaluate the membrane, the life of orthopositronium in the polyamide resin in the dry state is measured by a positron life measuring method. The life of orthopositronium means the time from the formation of orthopositronium by the linking of positrons implanted into a substance to each electron in the substance to the vanishment of the orthopositronium. A composite reverse osmosis membrane having 1.2-4.0 ns life of orthopositronium is used and a soln. to be treated is led to the membrane and purified.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

FIELD OF THE INVENTION The present invention relates to a method for evaluating the performance of a composite reverse osmosis membrane having a high salt rejection and selectively separating components of a liquid mixture. The present invention also relates to a method for separating a liquid to be treated using a composite reverse osmosis membrane having specific physical properties. The composite reverse osmosis membrane evaluated in the present invention is suitable for production of ultrapure water, desalination of brackish water, and the like. Removal, recovery, and purification of wastewater.

[0002]

BACKGROUND OF THE INVENTION Hitherto, a composite reverse osmosis membrane in which a thin film having a substantial separation function is formed on a porous support has been known. As such reverse osmosis membranes, those in which a thin film made of a polyamide obtained by interfacial polymerization of a polyfunctional amine and a polyfunctional aromatic halide formed on a support are widely known (for example, see No. 55-147106, JP-A-62-121603, JP-A-63-218208 and JP-A-2-187135
No.).

[0003] These composite reverse osmosis membranes have high desalination performance and water permeability, but in recent ultrapure water systems, even higher desalination performance is required. In addition, for desalination of brackish water, etc., since various kinds of ions are contained in the raw water to be treated, a high degree of desalination performance for various ions is required. In the performance evaluation of such a reverse osmosis membrane, conventionally, it took time to stabilize the measurement conditions,
An evaluation method with high reproducibility and sufficient reliability has not been established.

[0004] It is an object of the present invention to provide a method for evaluating a composite reverse osmosis membrane having a high salt rejection rate with a short measurement time and excellent reliability.

[0005]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies on the problems relating to such a method for evaluating a composite reverse osmosis membrane, and have found that the ortho-positronium lifetime determined by the positron lifetime measurement method and the composite reverse osmosis are not limited. The inventors have found that there is a close relationship with the performance of the film, and have completed the present invention.

That is, the first invention of the present application provides a skin support comprising a polyamide resin formed by an interfacial reaction between a compound having two or more reactive amino groups and a polyfunctional acid halide. In the composite reverse osmosis membrane provided above, there is provided a method for evaluating the performance of a composite reverse osmosis membrane characterized by measuring the ortho-positronium lifetime in the polyamide resin in a dry state obtained by a positron lifetime measurement method. .

[0007] The second invention of the present application relates to a method in which a skin layer comprising a polyamide resin formed by an interfacial reaction between a compound having two or more reactive amino groups and a polyfunctional acid halide is used as a porous support. For the composite reverse osmosis membrane provided above, to measure the ortho-positronium lifetime in the polyamide resin in a dry state using a positron lifetime measurement method,
It is an object of the present invention to provide a method for treating a liquid in which a solution to be treated is introduced into a composite reverse osmosis membrane having a measured value of 1.2 to 4.0 ns to separate and purify the solution to be treated. The relative strength of ortho-positronium in the polyamide resin in the dry state determined by the positron lifetime measurement method of this composite reverse osmosis membrane is 5 to 15
%.

Further, the ortho-positronium lifetime and the relative intensity of ortho-positronium in the polyamide resin in a dry state determined by the positron lifetime measurement method of the composite reverse osmosis membrane are in the range of 1.3 to 1.8 ns and 7 to 11%, respectively. Is preferred.

(Evaluation method) The positron lifetime measuring method used in the present invention is a known measuring method itself.
Using a β + decay isotope, high-energy positrons are injected into a material, and the distribution of the time until the injected positrons disappear in the material (positron lifetime) is measured. The details of such a measuring method are described in The Chemical Society of Japan, Experimental Chemistry Course 14, pages 485-488, Maruzen (1992).
In the present invention, any known positron lifetime measuring device using a fast-fast coincidence method may be used to determine the ortho-positronium lifetime and relative intensity using the positron lifetime measurement method.

[0010] The life of ortho-positronium means the time from the generation of ortho-positronium produced by the combination of a positron injected into the above-mentioned substance with one electron in the substance and the disappearance thereof.

The relative intensity of ortho-positronium means the ratio of ortho-positronium to the total number of positrons injected into the above-mentioned substance.

Since the rate of disappearance of ortho-positronium in the insulating material is proportional to the overlap of the ortho-positronium with the electron layer that has oozed from the pore wall in the substance, the life of ortho-positronium decreases as the pore size decreases. Therefore, it is considered that the ortho-positronium lifetime reflects the vacancy state of the composite reverse osmosis membrane skin layer polymer composed of the polymer-based insulating material.

The first invention of the present application is to measure the life of ortho-positronium in a polyamide resin in a dry state obtained by a positron lifetime measurement method, and to quickly and accurately evaluate performance such as salt rejection. Can be.

In the second invention of the present application, the life of ortho-positronium in the polyamide resin in a dry state is measured for the composite reverse osmosis membrane using a positron lifetime measurement method. The solution to be treated is introduced into the composite reverse osmosis membrane having a time of 2 to 4.0 ns, and the solution to be treated is separated and purified. In this way, a highly accurate separation operation can be performed. Furthermore, it is preferable that the relative strength of ortho-positronium in the polyamide resin in a dry state determined by the electron lifetime measurement method of the skin layer of the composite reverse osmosis membrane used is 5 to 15%.

If the positronium life is less than 1.2 ns, the pore size of the composite reverse osmosis membrane skin layer becomes too small, and sufficient permeability for practical use cannot be obtained. On the other hand, if it exceeds 4.0 ns, the pore size of the composite reverse osmosis membrane skin layer becomes excessively large, and the salt rejection rate is lowered, which is not preferable.

The relative strength of ortho-positronium in the insulating material obtained by the positron lifetime measurement method is a measure of the number density of vacancies in the insulating material. In the polyamide resin, the relative strength of ortho-positronium in the polyamide resin in a dry state determined by a positron lifetime measurement method is 5 to 5.
Use of a 15% polyamide resin is preferable because a practical composite reverse osmosis membrane having a higher salt rejection can be obtained.

Although the reason for this is not clear, when the relative strength of ortho-positronium is less than 5%, adjacent vacancies are connected and relatively large vacancies are easily formed, so that the salt rejection rate is reduced. If it exceeds 15%, it is presumed that the pores are excessively fragmented, and sufficient permeability for practical use cannot be obtained.

Further, the polyamide resin has an ortho-positronium lifetime and an ortho-positronium relative strength of 1.3 to 1.8 ns and 7 to 11%, respectively, in a dry state obtained by a positron lifetime measurement method.
It is preferable to use a polyamide resin having the range described above because a more practical composite reverse osmosis membrane having a high salt rejection and permeability can be obtained.

(Composite Reverse Osmosis Membrane) In the composite reverse osmosis membrane used in the evaluation method of the present invention, a skin layer made of a polyamide resin is provided on a porous support. In order to form such a skin layer, a method of performing an interfacial reaction between a compound having two or more reactive amino groups and a polyfunctional acid halide on a porous support is preferably used, There is no particular limitation. As such a method, for example, first, an aqueous solution containing a compound having two or more reactive amino groups is coated on a porous support, and then a water-immiscible organic solvent containing a polyfunctional halide is used. The method of contacting with the aqueous solution phase and causing an interfacial reaction can be adopted.

Examples of the compound having two or more reactive amino groups include m-phenylenediamine, p-phenylenediamine, 1,3,5-triaminobenzene,
3,5-diaminobenzoic acid, 2,4-diaminotoluene,
Aromatic polyfunctional amines such as 2,4-diaminoanisole, amidole, xylylenediamine and ethylenediamine;
Examples include aliphatic polyfunctional amines such as propylene diamine and tris (2-aminoethyl) amine.

On the other hand, polyfunctional acid halides include:
For example, aromatic polyfunctional acid halides such as isophthalic acid dichloride, terephthalic acid dichloride, naphthalene dicarboxylic acid dichloride, biphenyl dicarboxylic acid dichloride, biphenylene dicarboxylic acid chloride, tomesic acid chloride, etc., propane tricarboxylic acid chloride, butane tricarboxylic acid chloride, glutaryl chloride , Aliphatic polyfunctional acid halides such as adipoyl chloride, cyclopropanetricarboxylic acid chloride, cyclobutanetetracarboxylic acid chloride, cyclopentanetricarboxylic acid chloride, cyclopentanetetracarboxylic acid chloride, cyclohexanetricarboxylic acid chloride, tetrahydrofurantetracarboxylic acid Chloride, cyclopentanedicarboxylic acid chloride, cyclobutanedicarboxylic acid Aliphatic polyfunctional acid halide such as Roraido like. These polyfunctional acid halides may be used alone or as a mixture.

The water-immiscible organic solvent for dissolving these halides is not particularly limited as long as it does not dissolve the porous support. Examples thereof include n-hexane and n-hexane.
Examples include paraffinic hydrocarbons such as pentane, n-heptane, n-octane, iso-octane, cyclohexane, and cyclopentane.

A solution of the compound having two or more reactive amino groups is brought into contact with a solution of a polyfunctional acid halide to carry out an interfacial reaction, whereby a crosslinked polyamide containing a main component on a porous support is formed. A composite reverse osmosis membrane having a thin film formed thereon is obtained.

The porous support for supporting the thin film is not particularly limited as long as it can support the thin film. Examples thereof include polysulfone, polyarylethersulfone such as polyethersulfone, polyimide, and polyvinylidene fluoride. And the like. In particular, because it is chemically, mechanically and thermally stable,
A porous support made of polysulfone or polyaryl ether sulfone is preferably used. The porous support is
Usually about 25-125 μm, preferably about 40-75
It has a thickness of μm, but is not necessarily limited to these.

An aqueous solution containing a compound having two or more reactive amino groups may be further used, for example, in polyvinyl alcohol, polyvinyl pyrrolidone, in order to facilitate film formation or to improve the performance of the obtained composite reverse osmosis membrane. ,
A polymer such as polyacrylic acid or a polyhydric alcohol such as sorbitol or glycerin can be contained. In addition, a surfactant such as sodium dodecylbenzenesulfonate, sodium dodecyl sulfate, and sodium lauryl sulfate can be contained. These surfactants are 2
This is effective in improving the wettability of the aqueous solution containing the compound having one or more reactive amino groups on the porous support. Furthermore, in order to promote the polycondensation reaction at the interface, sodium hydroxide or trisodium phosphate capable of removing hydrogen halide generated by the interface reaction is used, or an acylation catalyst or the like is used as a catalyst. It is also effective.

In the organic solvent solution containing the polyfunctional acid halide and the aqueous solution containing the compound having two or more reactive amino groups, the polyfunctional acid halide and the two or more reactive amino groups are combined. The concentration of the compound having is not particularly limited, but the polyfunctional acid halide is
Usually 0.01 to 5% by weight, preferably 0.05 to 1% by weight
It is. Compounds having two or more reactive amino groups are
Usually 0.1 to 10% by weight, preferably 0.5 to 5% by weight.

In this way, the porous support is coated with an aqueous solution containing a compound having two or more reactive amino groups, and then coated with an organic solvent solution containing a functional acid halide. After that, the excess solution is removed respectively, and then usually about 20 to 150 ° C., preferably about 7 ° C.
0 to 130 ° C. for about 1 to 10 minutes, preferably about 2 to 8
After heating and drying for a minute, a water-permeable thin film made of a crosslinked polyamide is formed. This thin film usually has a thickness
It is in the range of 0.05 to 1 μm.

Further, the reverse osmosis membrane obtained by the production method of the present invention is chlorinated with hypochlorous acid or the like as described in JP-B-63-36803 to further reduce the salt rejection. It can also be improved.

[0029]

EXAMPLES Next, the present invention will be described more specifically with reference to examples, but the present invention is not limited to these examples.

Example 1 m-phenylenediamine 2.
An aqueous solution containing 0% by weight and 0.25% by weight of sodium lauryl sulfate was brought into contact with the porous polysulfone support for several seconds to remove excess aqueous solution and form a layer of the aqueous solution on the porous polysulfone support. .

Next, a hexane solution containing 0.2% by weight of trimesic acid chloride was brought into contact with the surface of the porous polysulfone support, and then kept in a hot-air dryer at 120 ° C. for 5 minutes to form a porous polysulfone support. A composite reverse osmosis membrane having a skin layer made of a polyamide resin on a support was obtained. About 1 m ² of the composite reverse osmosis membrane was immersed in dimethyl sulfoxide to dissolve the polysulfone as a support, thereby recovering the polyamide resin in the skin layer portion remaining as a solid. The recovered polyamide resin was sufficiently washed with ultrapure water to remove dimethyl sulfoxide, and then vacuum dried at 60 ° C. to obtain 0.12 g of a dried polyamide resin. Positron lifetime measurement of the dried polyamide resin showed that the ortho-positronium lifetime and its relative strength were 1.5 ns and 9.8%, respectively. Therefore, this polyamide resin satisfied the conditions of the present invention. The time required for the positron lifetime measurement was 2 hours.

Next, regarding the composite reverse osmosis membrane, 0.0
Using a saline solution having a pH of 7 containing 5% by weight of sodium chloride as a feed solution and performing evaluation by a reverse osmosis test at a pressure of 0.75 MPa, the salt rejection by the permeate conductivity was 99.
7%, the permeation flux was 1.0 m ³ / m ² · day. In addition,
The time required to evaluate about 1 m ² of the composite reverse osmosis membrane in the reverse osmosis test was 94 hours.

[0033]

According to the present invention, a composite reverse osmosis membrane having a high salt rejection can be evaluated in a short time and by a highly reliable method. In addition, since the area of the film to be evaluated can be reduced and measured in a short time, statistical data analysis is possible. Further, unlike the conventional case, power and pressure for evaluation are not required, the evaluation system is simple, and the evaluation operation can be easily performed by unmanned automatic operation. Operation of the ultrapure water production process required for desalination of brackish water, seawater, etc. and for the production of semiconductors, because a highly practical composite reverse osmosis membrane with a high salt rejection ratio can be easily and accurately evaluated. Contribute to management.

Claims (4)

[Claims] 1. A composite reverse osmosis membrane in which a skin layer made of a polyamide resin formed by an interfacial reaction between a compound having two or more reactive amino groups and a polyfunctional acid halide is provided on a porous support. 3. The method for evaluating the performance of a composite reverse osmosis membrane according to claim 1, wherein the orthopositronium lifetime in the polyamide resin in a dry state obtained by a positron lifetime measurement method is measured. 2. A composite reverse osmosis membrane in which a skin layer comprising a polyamide resin formed by an interfacial reaction between a compound having two or more reactive amino groups and a polyfunctional acid halide is provided on a porous support. Of the polyamide resin in a dry state using a positron lifetime measurement method, and the measured value was 1.2 to 4.0 ns.
A method for treating a liquid, comprising introducing a solution to be treated into a composite reverse osmosis membrane, and separating and purifying the solution to be treated. 3. The method for treating a liquid according to claim 2, wherein the relative strength of ortho-positronium in the polyamide resin in a dry state determined by an electron lifetime measurement method is 5 to 15%. 4. The life of ortho-positronium and the relative strength of ortho-positronium in a polyamide resin in a dry state determined by a positron lifetime measurement method are 1.3 to 1.
3. The method of claim 2 wherein said liquid is in the range of 8 ns and 7-11%.