JPH0613086B2 - Membrane separation treatment method for non-electrolyte containing solution - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial field of application> The present invention provides a non-electrolyte removal rate by using a semi-permeable membrane that has been subjected to a specific pretreatment when a solution containing a non-electrolyte is subjected to membrane separation treatment. The present invention relates to a method for membrane separation treatment of a non-electrolyte-containing solution that can improve the permeation rate without substantially reducing the above.

<Prior art and its problems> A semipermeable membrane made of aromatic polysulfone having excellent heat resistance and pH resistance is used for removal and concentration of solute in a solution.
There was a drawback that the permeation rate was low relative to the solute removal rate. As a means for solving such a drawback, it is known that a sulfonic acid group is introduced into a side chain of an aromatic polysulfone, that is, the aromatic polysulfone is sulfonated to increase hydrophilicity, thereby improving the permeation performance of a semipermeable membrane. . However, in such a sulfonated aromatic polysulfone, in order to further improve the permeation rate, it is necessary to increase the sulfonic acid group content of the sulhenated aromatic polysulfone as a membrane material as much as possible. The higher the content, the higher the permeation rate of the membrane, but the lower the removal rate.

<Means for Solving Problems> As a result of intensive studies for solving the above-mentioned drawbacks of the prior art, the present inventors have found that, particularly when a non-electrolyte-containing solution is subjected to a membrane separation treatment, a sulfonated aromatic group having a sulfonic acid group. By using a specific pretreatment semipermeable membrane for the polysulfone-based semipermeable membrane, the permeation rate can be improved without increasing the sulfonic acid group content of the initial semipermeable membrane,
That is, the inventors have found that the permeation rate can be improved without lowering the removal rate of the non-electrolyte, and arrived at the present invention.

That is, the present invention, when performing the membrane separation treatment of the non-electrolyte-containing solution, using a sulfonated aromatic polysulfone-based semipermeable membrane treated with an aqueous solution of an alkali metal salt, to remove the non-electrolyte from the non-electrolyte-containing solution. The present invention provides a characteristic method for membrane separation treatment of a non-electrolyte-containing solution.

Examples of the non-electrolyte-containing solution to which the present invention is applied include glycols such as ethylene glycol, triethylene glycol and polyethylene glycol, saccharose, glucose, and solutions containing non-electrolytes such as saccharides such as fructose. It is not limited to these.

The sulfonated aromatic polysulfone-based semipermeable membrane in the present invention has a sulfonic acid group —SO ₃ ^— (M ^{n +} ) ^{1 / n} [M ^{n +} represents an n-valent cation] on the side chain of the aromatic polysulfone-based polymer. It is not particularly limited as long as it is a semipermeable membrane made of the polymer. Specific examples of the sulfonic acid group include -SO ₃ Na, -SO ₃ Li,-
(SO ₃ ) ₂ Mg, —SO ₃ H and the like can be mentioned. Further, the degree of sulfonation may be such that the sulfonated aromatic polysulfone contains a sulfonic acid group such that the ion exchange capacity is usually about 0.5 to 2.3 meq / g.

Specific examples of the sulfonated aromatic polysulfone-based polymer, the following repeating unit (A) A polymer obtained by sulfonation of an aromatic polysulfone polymer, or the repeating unit (A) and the following repeating unit (B) A copolymer obtained by sulfonation of an aromatic polysulfone copolymer consisting of, wherein the repeating unit (A) is 10 mol% or more and the repeating unit (B) is 90 mol% or less. To be As such a polymer, a water-insoluble polymer having an inherent viscosity of 0.5 or more, preferably 0.7 or more and an ion exchange capacity of 2 meq / g or less is used. Here, the logarithmic viscosity means that 0.5 g of the polymer is N-methyl-
30 ℃ for a solution dissolved in 100 ml of 2-pyrrolidone
It is the value measured in. (The same shall apply hereinafter.) In the present invention, the following repeating unit (C) A polymer obtained by sulfonation of an aromatic polysulfone polymer composed of

The form of the semipermeable membrane made of the sulfonated aromatic polysulfone-based polymer is not particularly limited, and may be a homogeneous membrane, an asymmetric membrane, or a composite membrane in which a semipermeable membrane is formed on an ultrapermeable membrane as a support. Used.

In the present invention, a non-electrolyte-containing solution is subjected to membrane separation treatment using a specific semipermeable membrane obtained by pretreating a semipermeable membrane made of such a sulfonated aromatic polysulfone polymer with an aqueous solution of an alkali metal salt described below. It is a thing.

Examples of the alkali metal salt include potassium chloride, sodium chloride, potassium nitrate, sodium nitrate and the like. Examples of the method of pretreating the semipermeable membrane with an aqueous solution of an alkali metal salt include, but are not particularly limited to, a method of immersing the membrane in the aqueous solution and a method of allowing the aqueous solution to permeate the membrane. Although the concentration of the aqueous solution of the alkali metal salt is appropriately selected according to the treatment method, it is preferably 1 to 10% when the treatment is performed by immersion, and preferably 100 when the treatment is permeated.
˜20,000 ppm, and more preferably 1,000 to 10,000 ppm.
The immersion treatment time is usually 5 minutes or more and 10 hours or less, preferably 1 to 5 hours. The conditions for the permeation treatment are as follows: the temperature is 5 to 80 ° C., preferably 20 to 50 ° C., the operating pressure is 5 to 70 kg / cm ² , preferably 10 to 50 kg / cm ² , and the permeation time is 5 minutes to 5 hours. It is preferably 20 minutes to 2 hours.

In the present invention, by treating a semipermeable membrane made of a sulfonated aromatic polysulfone-based polymer with an aqueous solution of an alkali metal salt as described above, the cation of the sulfonic acid group is substituted with the above alkali metal ion, which is the reason. Is not always clear, but with this treated semipermeable membrane,
When the non-electrolyte-containing solution is subjected to the membrane separation treatment, the permeation rate can be improved without lowering the removal rate of the non-electrolyte.

<Effect> As described above, according to the present invention, when the solution containing the non-electrolyte is subjected to the membrane separation treatment, by using the sulfonated aromatic polysulfone-based semipermeable membrane which has been subjected to a specific pretreatment, There is an advantage that the permeation rate can be improved without increasing the sulfonic acid group content of the semipermeable membrane, that is, without reducing the removal rate of the non-electrolyte.

<Examples> The present invention will be specifically described below with reference to Examples. In addition,
The removal rate and the permeation rate were calculated by the following equations.

Example 1 An aromatic polysulfone having the following repeating unit Sulfonated to have a sulfonic acid group -SO ₃ Na, and an inherent viscosity of 3.00, an ion exchange capacity of 1.92 meq /
A homogeneous membrane (thickness: about 1 μm) consisting of sulfonated polyethersulfone (g) was permeabilized with an aqueous solution of 5000 ppm potassium chloride under a pressure of 50 kg / cm ² and a temperature of 25 ° C. for 0.5 hour, and then the semipermeable membrane was formed. When a 500 ppm aqueous solution of triethylene glycol was treated under the same conditions, the removal rate was 20% and the permeation rate was 2.0 m ³ / m ² .day.

Comparative Example 1 A 500 ppm aqueous solution of triethylene glycol was used in Example 1 using the semipermeable membrane of Example 1 before permeation of an aqueous potassium chloride solution.
When treated under the same conditions as above, the removal rate was 21% and the permeation rate was 1.5 m ³ / m ² .day.

Example 2 Consists of the following repeating units A composite having an anisotropic ultrafiltration membrane of polysulfone having a removal rate of 10% for polyethylene glycol having an average molecular weight of 20,000 as a support and having the sulfonated polyethersulfone of Example 1 in a skin layer (thickness: about 5000Å) Semipermeable membrane,
Removal rate when permeabilized with a potassium chloride 5000 ppm aqueous solution at a working pressure of 30 kg / cm ² and a temperature of 25 ° C. for 0.5 hour, and then treated with a sucrose 500 ppm aqueous solution under the same conditions using such a composite semipermeable membrane. Is 50%, transmission speed is 2.5m
^{It was 3} / m ² .day.

Comparative Example 2 Using the composite semipermeable membrane of Example 2 prior to permeation of an aqueous potassium chloride solution, a 500 ppm aqueous saccharose solution was treated under the same conditions as in Example 2. The removal rate was 52.5% and the permeation rate was
It was 1.8 m ³ / m ² .day.

Example 3 The anisotropic unit of polysulfone used in Example 2 was used as a support and the repeating unit A was used. And repeating unit B A polyether sulfone copolymer having 57 mol% of repeating units A and 43 mol% of repeating units B is sulfonated to have a sulfonic acid group —SO ₃ Na and has a logarithmic viscosity of 0.84. , A composite semipermeable membrane with a sulfonated polyethersulfone with an ion exchange capacity of 1.3 meq / g in the skin layer (thickness about 5000Å), potassium chloride
After permeabilization with 5000 ppm aqueous solution for 1 hour under the operating pressure of 30 kg / cm ² and temperature of 25 ° C., the removal rate was 97.2% when the sucrose 500 ppm aqueous solution was treated under the same conditions using the composite semipermeable membrane. The permeation rate was 0.56 m ³ / m ² .day.

Comparative Example 3 When the same treatment as in Example 3 was performed using the composite semipermeable membrane of Example 3 prior to permeation of an aqueous potassium chloride solution, the sucrose removal rate was 97.5% and the permeation rate was 0.45 m ³ / m ² .day. Met.

Example 4 Instead of sulfonic acid group —SO ₃ Na in Example 2, —SO ₃ Li
The same composite semipermeable membrane as in Example 2 except that a sulfonated polyether sulfone having
0.5 in an aqueous solution at a pressure of 30 kg / cm ² and a temperature of 25 ° C.
After time permeation treatment, a 500 ppm triethylene glycol aqueous solution was treated under the same conditions using the composite semipermeable membrane, and the removal rate was 19% and the permeation rate was 4.0 m ³ / m ² .day.

Comparative Example 4 Using the composite semipermeable membrane of Example 4 prior to permeation of an aqueous potassium chloride solution, a 500 ppm triethylene glycol aqueous solution was treated under the same conditions as in Example 4, and the removal rate was 20%.
The permeation rate was 3.4 m ³ / m ² .day.

Example 5 Example 4 is the same as Example 4 except that the treatment was performed with a 5000 ppm aqueous solution of sodium chloride instead of the potassium chloride aqueous solution.
When measured under the same conditions as above, the removal rate of triethylene glycol was 23%, and the permeation rate was 3.8 m ³ / m ² .day.

Example 6 Instead of the sulfonic acid group —SO ₃ Na in Example 1 — (SO ₃ ).
_The same homogeneous membrane as in Example 1 except that it had ₂ Mg was permeated with a 5000 ppm aqueous solution of potassium chloride under the same conditions as in Example 1, and the same measurement as in Example 1 was conducted using the semipermeable membrane. The ethylene glycol removal rate was 19%, and the permeation rate was 2.0 m ³ / m ² .day.

Comparative Example 5 When the same measurement as in Example 6 was carried out using the semipermeable membrane of Example 6 prior to permeation of an aqueous potassium chloride solution, the removal rate was 17
%, The permeation rate was 1.2 m ³ / m ² .day.

Claims (1)

[Claims] 1. When a non-electrolyte-containing solution is subjected to a membrane separation treatment,
A method for membrane separation treatment of a non-electrolyte-containing solution, which comprises removing the non-electrolyte from the non-electrolyte-containing solution by using a sulfonated aromatic polysulfone-based semipermeable membrane treated with an aqueous solution of an alkali metal salt.