JPH1128466A - Reverse osmosis treatment method of water by reverse osmosis composite membrane - Google Patents

Abstract

(57) Abstract: A reverse osmosis treatment using a reverse osmosis composite membrane having a protective layer formed on the surface of a reverse osmosis composite membrane having a skin layer having a specific surface area of 2 or more and 1000 or less at a recovery rate of 75% or more. By doing so, there is no problem that film contamination does not progress rapidly, scale components of inorganic substances such as silica and calcium do not easily adhere to the film surface, and trace organic substances such as surfactants do not easily adsorb to the film surface. A method for reverse osmosis treatment of water with a reverse osmosis composite membrane is provided. The surface of a microporous polysulfone support membrane is m-
The aramid film obtained by reacting phenylenediamine and trimesic acid chloride is heat-treated to form a skin layer, a polyvinyl alcohol solution having a saponification degree of 99% is applied to the surface, and dried to form a composite reverse osmosis membrane. obtain. Reverse osmosis treatment is performed using the membrane at a recovery rate of 75% or more, preferably 90% or more.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a reverse osmosis treatment method for water using a reverse osmosis composite membrane. More specifically, with a high recovery rate using a reverse osmosis composite membrane having an organic polymer thin film on a reverse osmosis composite membrane, a high salt rejection rate, a high chlorine disinfectant resistance, and a high contamination resistance, etc. Related to the driving method. Such a reverse osmosis composite membrane can be operated stably for a long period of time by suppressing a decrease in water permeability, which is an adverse effect at a high recovery rate.

[0002]

BACKGROUND ART Reverse osmosis membranes used industrially include:
As an asymmetric membrane made of cellulose acetate, for example, there is a lob type membrane described in US Pat. No. 3,133,132 or US Pat. No. 3,133,137. On the other hand, as a reverse osmosis membrane having a structure different from that of an asymmetric reverse osmosis membrane, a reverse osmosis composite membrane formed by forming an active thin film having substantially selective separation on a microporous support membrane is known.

At present, many of such reverse osmosis composite membranes are known in which a thin film made of polyamide obtained by interfacial polymerization of a polyfunctional aromatic amine and a polyfunctional aromatic acid halide is formed on a support membrane. (For example,
55-147106, JP-A-62-121603, JP-A-63
-218208, JP-A-2-187135, etc.).

Further, a thin film made of a polyamide obtained by interfacial polymerization of a polyfunctional aromatic amine and a polyfunctional alicyclic acid halide is formed on a support film (for example, see Japanese Patent Application Laid-Open No. H11-163873). No. 61-42308, etc.).

Further, various methods for post-treating a reverse osmosis membrane have been disclosed. For example, an example in which various organic polymers are used as a protective layer is disclosed (for example, Japanese Patent Application Laid-Open No. S51-1338).
No. 8, JP-A-53-16372, JP-A-62-197105, JP-B-7-90152, etc.).

[0006]

However, the above-mentioned conventional method has a problem that the water permeability is reduced due to the formation of the protective layer, and a practical level of water permeability cannot be obtained. or,
The application of reverse osmosis membranes to various water treatments, such as the production of ultrapure water (recovery system), sewage treatment, seawater desalination, etc., is expected. If the operation is performed at a higher recovery rate, for example, 1) membrane contamination rapidly progresses, and 2) operation is performed in a silica or calcium scale generation region. There is a problem that water permeability is reduced due to factors such as adhering to the surface and 3) a trace amount of organic substances such as a surfactant adsorbing to the film surface, and stable operation cannot be performed.

According to the present invention, in order to solve the above-mentioned conventional problems, film contamination does not proceed rapidly, scale components of inorganic substances such as silica and calcium hardly adhere to the film surface, and trace organic substances such as surfactants are present. It is an object of the present invention to provide a method for treating water using a reverse osmosis composite membrane which can be operated at a high recovery rate without a problem such that water is not easily adsorbed on a membrane surface.

[0008]

In order to achieve the above object, the method for reverse osmosis treatment of water using a reverse osmosis composite membrane according to the present invention is directed to a reverse osmosis composite membrane having a skin layer having a specific surface area of 2 to 1,000. The reverse osmosis treatment is performed at a recovery rate of 75% or more using a reverse osmosis composite membrane having a protective layer formed thereon. However, the recovery rate (%) = (permeation flow rate / supply flow rate) × 100.

In the above method, the recovery is preferably 90% or more. In the above method, the skin layer preferably has a specific surface area of 3 or more and 500 or less.

In the above method, it is preferable that the specific surface area of the skin layer of the reverse osmosis composite membrane is controlled to 90% or less as compared with that before forming the protective layer. In the above method, the protective layer is preferably a polymer coating layer.

In the above method, the protective layer preferably has a nonionic hydrophilic group. In the above method, the protective layer is insoluble in water at 25 ° C.,
It is preferably polyvinyl alcohol which is soluble in water at 80 ° C.

In the above method, the polyvinyl alcohol preferably has a saponification degree of 95% or more. Further, in the above method, a reverse osmosis composite membrane having a skin layer having a specific surface area of 2 or more and 1000 or less is formed under a pressure of 7.5 kgf / cm.
^{2. In} a reverse osmosis test under the condition of a temperature of 25 ° C. and a supply solution of 500 ppm of NaCl, the water permeability was 0.6
[M ³ / m ² / day] or more is preferable.

Further, in the above method, the reverse osmosis composite membrane having a protective layer formed on the surface is formed under a pressure of 15 kgf / cm ² and a temperature of 25 kgf / cm ² .
In a reverse osmosis test under the condition of a NaCl solution containing 1,500 ppm of a feed solution at a temperature of 600 ° C., the water permeability was 0.6 [m ³ / m ² /
Days] or more.

In the method of the present invention, reverse osmosis treatment can be effectively performed even with water containing a transition metal component. Here, the transition metal component-containing water means, regardless of the concentration and the type of the transition metal component,
In addition, the water may contain various other salts and organic substances. For example, in the treated raw water such as seawater, sewage, boiler water, industrial water, industrial drainage, landfill leachate, etc., the transition metal component is contained as an elute from the pipe inner wall, pump, etc. when flowing through the pipe, etc. Is the water that you do.

In the present invention, the control method for reducing the specific surface area of the reverse osmosis composite membrane is not particularly limited. However, it is preferable that the surface of the reverse osmosis composite membrane is coated with an organic substance or an organic polymer of a skin layer. Such organic matter,
Or, as the organic polymer, silicon rubber, fluorine-based polymer such as polyethylene terephthalate, sulfonated polysulfone, sulfonic acid group-containing organic polymer such as sulfonated polyether sulfone, amino group-containing organic polymer such as polyethyleneimine, polyimide Etc., but for the purpose of maintaining high water permeability after coating, an organic substance having a hydrophilic group, or an organic polymer, particularly having a nonionic hydrophilic group for the purpose of suppressing charge adsorption. Organic substances or organic polymers are preferred. The nonionic hydrophilic group is, for example, —OH, —NHCO—, —O—, or a group represented by the following formula (Formula 1).

[0016]

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Examples of the organic material or organic polymer having a nonionic hydrophilic group include nonionic hydrophilic materials such as polyvinyl alcohol, saponified polyethylene-vinyl acetate copolymer, polyvinylpyrrolidone, hydroxypropylcellulose and polyethylene glycol. It is selected from a vinyl polymer having a functional group, a condensation polymer, an addition polymer and the like. A more preferred organic polymer is a water-insoluble organic polymer having a nonionic hydrophilic group soluble in hot water at 25 ° C., for example, polyvinyl alcohol.

When polyvinyl alcohol is used, it preferably has a degree of saponification of 99 to 100%. In this case, polyvinyl alcohol becomes water-insoluble at 25 ° C. due to hydrogen bonding between molecular chains, but is soluble in hot water. Satisfying these conditions is due to an increase in hydrophilicity due to a large amount of -OH groups on the membrane surface in contact with the treated water, thereby increasing the ability to suppress the adsorption of transition metal components and increasing the amount of permeated water. This is preferable because good film performance can be added to the above.

[0019]

BEST MODE FOR CARRYING OUT THE INVENTION A specific preparation method for coating a reverse osmosis composite membrane surface with an organic substance or an organic polymer will be described below. The reverse osmosis composite membrane to be used is not particularly limited, and there is a polyamide-based, polyurea-based or the like formed by an interfacial polymerization method. These films can be easily obtained by a conventionally known method or the like. For example, using a porous polysulfone support membrane, metaphenylenediamine,
After applying an aqueous solution of a monomer or polymer having a reactive amino group such as piperazine or polyethyleneimine to at least one surface of the porous polysulfone support membrane, trimesic acid chloride, polyfunctional acid chloride such as isophthalic acid chloride, or By contacting with a solvent such as hexane of a polyfunctional isocyanate such as a diisocyanate or a mixture thereof, an interfacial polymerization is performed on a porous polysulfone support membrane to form a film having a desalination performance to form a reverse osmosis composite membrane. be able to.

The specific surface area of the skin layer of these reverse osmosis composite membranes is preferably 2 or more and 1000 or less, more preferably 3 or more and 500 or less in order to have high water permeability. If the specific surface area is less than 2, a sufficient water permeability cannot be obtained after the coating treatment described below,
On the other hand, if it is larger than 1000, uniform coating cannot be performed. Further, if the number is 3 or more and 500 or less, the performance of the obtained composite reverse osmosis membrane is 7.5 (kgf / c).
m ² ), the permeation flux after permeating an aqueous solution of pH 6.5 containing 500 ppm of sodium chloride at a temperature of 25 ° C. for 1 hour becomes 0.6 (m ³ / m ² / day) or more, and the permeation flux is permeated by the coating treatment. It is possible to obtain a reverse osmosis composite membrane having no practical problem even if its performance is reduced.

The specific surface area used in the present invention is defined by the following equation. Skin layer specific surface area = (surface area of skin layer) / (surface area of microporous support)

The surface area of the skin layer indicates the surface area of the surface opposite to the surface in contact with the microporous support, that is, the surface in contact with the supply liquid. On the other hand, the specific surface area of the microporous support represents the surface area of the surface in contact with the skin layer.

The method for determining the surface area and the specific surface area can be a general measurement method (for example, a surface area measuring device, a specific surface area measuring device, a scanning electron microscope, a transmission electron microscope, an atomic force microscope, etc.) and is particularly limited. It is not something to be done.

A solution of the above organic substance or organic polymer, preferably an organic substance having a nonionic hydrophilic group, or an organic polymer is applied to such a reverse osmosis composite membrane, and then dried. To obtain a final reverse osmosis composite membrane with controlled surface charge. Organic substances, or organic polymers are solvents, water, which do not damage the active film layer of the reverse osmosis composite membrane,
It is used by dissolving it in a lower alcohol, a halogenated hydrocarbon, an aliphatic hydrocarbon, acetone, acetonitrile, or a mixed solution of at least two of them. Among these solvents, aliphatic alcohols such as methanol, ethanol, propanol and butanol, halogenated aliphatic alcohols such as ethylene chlorohydrin, methoxymethanol, methoxyethanol, and mixtures of at least one of these lower alcohols with water are preferred. Solvents can be mentioned. In the case of a mixed solvent, the ratio of the lower alcohol to water is not particularly limited.
% To 90%. When water is used as the solvent, it is also preferable to add a surfactant for the purpose of improving the wettability with the film.

The concentration of the above-mentioned organic substance or organic polymer having a nonionic hydrophilic group prepared using the above solvent is 0.01 to 20% by weight, preferably 0.05 to 5% by weight. A range is preferred. Such a coating method is not particularly limited, but a dipping method, a transfer method, a spray method and the like are preferably used. The drying means after application and the drying temperature are not particularly limited either, but are preferably in the range of 20C to 200C, preferably in the range of 50C to 150C.

The thickness of the thin film thus obtained on the reverse osmosis composite membrane is 0.001 to 1 μm, preferably 0.01 to 1 μm.
A thickness of about 0.5 to 0.5 μm is suitable for suppressing a decrease in water permeability due to coating. The method for controlling the film thickness is not particularly limited, but can be controlled by the solution concentration or the like.

Further, the water permeability of the composite reverse osmosis membrane having the obtained organic polymer in the surface layer is 15 (kgf / c
m ² ), temperature 25 ° C., feed solution 1500 ppm NaCl
The water permeability is 0.1 (m ³ / m ² / day) or more under the condition of
It is preferably 0.6 (m ³ / m ² / day) or more for practical operation.

[0028]

EXAMPLES The present invention will be described below with reference to examples.
The present invention is not limited to these examples.

[0029]

EXAMPLE 1 3.0% by weight of triethylamine, 6.0% by weight of camphorsulfonic acid and 5.0% by weight of isopropyl alcohol in an aqueous solution containing 3.0% by weight of m-phenylenediamine and 0.15% by weight of sodium lauryl sulfate. After contacting the aqueous solution containing 0% by weight with the microporous polysulfone support membrane for several seconds, the excess aqueous solution was removed to form a layer of the aqueous solution on the support membrane.

Next, the surface of the support membrane is contacted with an IP1016 (isoparaffinic hydrocarbon oil manufactured by Idemitsu Chemical Co., Ltd.) solution containing 0.20% by weight of trimesic acid chloride and 0.05% by weight of isopropyl alcohol. I let it. Then, it was kept in a hot air dryer at 120 ° C. for 3 minutes to form a skin layer on the support to obtain a composite reverse osmosis membrane. Wash the obtained composite reverse osmosis membrane sufficiently, evaluate the membrane performance,
After drying, the cross section of the composite reverse osmosis membrane was observed with a transmission electron microscope, and the specific surface area of the skin layer was measured. [Table 1]
Shown in The specific surface area of the skin layer was 4.3.

On the surface of the composite reverse osmosis membrane obtained in the same manner,
0.25% by weight of a polyvinyl alcohol (n = 2,000) solution having a saponification degree of 99% (isopropyl alcohol /
(Water = 3/7), and dried at 130 ° C. for 5 minutes to obtain a composite reverse osmosis membrane of the present invention. The obtained composite reverse osmosis membrane was sufficiently washed, the membrane performance was evaluated, and after drying, the cross section of the composite reverse osmosis membrane was observed with a transmission electron microscope to measure the specific surface area of the skin layer. The film performance is shown in [Table 1].

[0032]

[Table 1]

The specific surface area of the skin layer was 2.0 (47% specific surface area before treatment). Using an element obtained by spirally winding the obtained flat membrane, 5 μm of industrial well water was used.
Cartridge filter (Model: TCW-5N-PP
S: Water (silica concentration: 50 ppm) treated with Advantech Toyo Co., Ltd. was pressurized and circulated under a pressure of 15 kgf / cm ² at a recovery rate of 95% for 100 hours.

[0034]

[Comparative Example 1] A resistance test similar to the above [Example 1] was performed by comparing a composite reverse osmosis membrane having the same reverse osmosis membrane performance as that of a surface treatment membrane with polyvinyl alcohol.

[0035]

[Table 2] From the above examples, it was confirmed that the reverse osmosis treatment method of the present invention can be operated at a high recovery rate.

[0036]

As described above, according to the method for treating water using the composite reverse osmosis membrane of the present invention, the specific surface area is 2 or more and 1 or more.
By using a reverse osmosis composite membrane having a protective layer formed on the surface of a reverse osmosis composite membrane having a skin layer of 000 or less and performing reverse osmosis treatment at a recovery rate of 75% or more, membrane contamination does not rapidly advance, Provided is a reverse osmosis treatment method for water using a reverse osmosis composite membrane, which does not have a problem that a scale component of an inorganic substance such as silica or calcium hardly adheres to a membrane surface and a trace amount of an organic substance such as a surfactant is hardly adsorbed on the membrane surface. be able to.

Claims (10)

[Claims] In a reverse osmosis treatment method for water using a reverse osmosis composite membrane, a reverse osmosis composite membrane having a protective layer formed on the surface of a reverse osmosis composite membrane having a skin layer having a specific surface area of 2 to 1,000 is used. A reverse osmosis treatment using a reverse osmosis composite membrane, wherein the reverse osmosis treatment is performed at a recovery rate of 75% or more. However, recovery rate (%) = (permeation flow rate / supply flow rate) × 10
0 2. The method for reverse osmosis treatment of water using a reverse osmosis composite membrane according to claim 1, wherein the recovery rate is 90% or more. 3. The reverse osmosis treatment method for water using a reverse osmosis composite membrane according to claim 1, wherein the specific surface area of the skin layer is 3 or more and 500 or less. 4. The specific surface area of the skin layer of the reverse osmosis composite membrane is as follows:
The method for reverse osmosis treatment of water with a reverse osmosis composite membrane according to claim 1, wherein the water content is controlled to 90% or less as compared with that before forming the protective layer. 5. The method according to claim 1, wherein the protective layer is a polymer coating layer. 6. The reverse osmosis treatment method for water using a reverse osmosis composite membrane according to claim 1, wherein the protective layer has a nonionic hydrophilic group. 7. The method for reverse osmosis treatment of water using a reverse osmosis composite membrane according to claim 1, wherein the protective layer is a polyvinyl alcohol which is insoluble in water at 25 ° C. and soluble in water at 80 ° C. 8. Polyvinyl alcohol having a saponification degree of 95%
The method for reverse osmosis treatment of water using the reverse osmosis composite membrane according to claim 7. 9. A reverse osmosis composite membrane having a skin layer having a specific surface area of 2 or more and 1000 or less in a reverse osmosis test under the conditions of a pressure of 7.5 kgf / cm ² , a temperature of 25 ° C., and a supply solution of 500 ppm of NaCl solution. Has a water permeability of 0.6 [m ³ / m ²
/ Day] or more, the reverse osmosis treatment method of water using the reverse osmosis composite membrane according to claim 1. 10. A reverse osmosis composite membrane to form a protective layer on the surface, pressure 15 kgf / cm ^2, temperature of 25 ° C., feed 1500p
In a reverse osmosis test under the condition of pm NaCl solution,
The reverse osmosis treatment method for water using a reverse osmosis composite membrane according to claim 1, wherein the water permeability is 0.6 [m ³ / m ² / day] or more.