JPS5955311A - Regenerating method of permselective membrane - Google Patents

Abstract

PURPOSE:To restore easily the decreased performance of a permeable membrane by treating the polypeptide deposited strongly on the membrane surface with an aq. soln. contg. alkali metal salts and/or alkaline earth metals and a halogen oxidizing agent. CONSTITUTION:When a reverse osmotic membrane consisting of cellulose acetate is mounted to a flow type cell and an extracted liquid of fermentation is supplied to said cell continuously for 100hr at an ordinary temp. and 40kg/cm<2> pressure, the rate of permeation decreases from initial 0.70m<3>/m<2>.day to 0.20m<3>/m<2>. day. Thereupon when an aq. soln. contg. 2wt% sodium sulfate and 10ppm sodium dihypochlorite is circulated to the cell for 1hr under the conditions of 25 deg.C and 3kg/cm<2> pressure, the rate of permeation is recovered up to 93% of the initial rate. The rate of permeation decreased as a result of contamination with polypeptide after the membrane is used in handling process liquids for food, medical goods, fermentation, etc., is recovered in a shoft time by the simple operation.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for regenerating a selectively permeable membrane, and more specifically, the present invention relates to a method for regenerating a selectively permeable membrane. The present invention relates to a method for regenerating a selectively permeable membrane that removes polypeptides and restores its membrane performance.

In recent years, membrane treatment using selective permeable membranes such as reverse osmosis membranes and ultrafiltration membranes has been put into practical use in the treatment of industrial wastewater, separation and concentration processes in the production of foods, medicines, chemicals, etc. It has been reached. However, in such membrane treatment, components in the treatment stock solution, especially organic substances, gradually deposit on the membrane surface and contaminate the membrane, so that a decrease in membrane performance, especially water permeation rate, is unavoidable.

Therefore, various methods have been proposed in the past for cleaning the membrane surface on which organic substances have been deposited and restoring the membrane performance.

For example, methods using aqueous solutions of anionic and nonionic surfactants such as commercially available synthetic detergents, methods using aqueous solutions of enzymes such as protease and α-amylase, and methods using oxidizing agents such as hypochlorite and hydrogen peroxide. However, depending on the deposited substances, these methods have little effect on removing the deposited substances from the membrane surface, or take an extremely long time to recover the membrane performance, and furthermore, they may deteriorate the membrane. There are also issues such as how to In particular, membranes contaminated with polypeptides such as proteins do not easily recover membrane performance by conventional cleaning methods.

The present inventors have conducted extensive research to solve the above-mentioned problems, and have found that polypeptides are deposited on the membrane surface, resulting in a selectively permeable membrane with reduced membrane performance. The present invention was achieved based on the discovery that by washing with an aqueous solution, the polypeptide can be removed in a short time and the membrane performance can be easily restored.

The method for regenerating a selectively permeable membrane according to the present invention includes regenerating a selectively permeable membrane in which a polypeptide is deposited on the membrane surface by using a method containing at least one selected from alkali metal salts and alkaline earth metal salts and a halogen-based oxidizing agent. It is characterized by being treated with an aqueous solution.

In the present invention, a selectively permeable membrane typically refers to a membrane that does not selectively permeate a specific solute component in a solution, such as a reverse osmosis membrane or an ultrafiltration membrane, and various types of membranes are already available. Are known. Specific examples include anisotropic membranes made of polymers such as cellulose esters such as cellulose acetate, polyamides, polyimides, polyhenzimidazolone, polysulfones, polyethersulfones, sulfonated polysulfones, polyolefins, polyvinyl chloride, and polyacrylonitrile. Alternatively, there may be mentioned a composite membrane in which an ultra-thin membrane made of polyamide, polyurea, polyfuran, etc. is directly formed on a Bossulphone ultrafiltration membrane. However, the film to which the method of the present invention can be applied does not contain the halogen-based oxidizing agent described below.
It is required that it not be deteriorated by an aqueous solution containing 9111 or more.

In the present invention, polypeptides refer to oligomers and polymers whose main chains are formed by peptide bonds, but their molecular weights are not particularly limited. Includes up to Representative examples of such polypeptides are proteins. Contamination of a membrane with such polypeptides can be determined by surface analysis means such as, for example, infrared absorption spectroscopy. Polypeptides are often contained in food, medicine, fermentation, and other processes, and are also excreted in large quantities from the manufacturing process.

The alkali metal salts and alkaline earth metal salts used in the present invention are water-soluble salts of lithium, sodium, potassium, calcium, magnesium, etc., and are preferably water-soluble neutral salts whose aqueous solution has a p■ of 6 to 8. It is a salt, and neutral salts such as sulfate, hydrohalide, and phosphate are preferably used.

Here, water-soluble means 1% by weight in water at room temperature.
It means that the solubility is higher than that. Therefore, preferably sulfates and hydrohalides are used. Preferred specific examples of the neutral salts include sulfates such as sodium sulfate, potassium sulfate, and magnesium sulfate, lithium chloride,
Examples include hydrohalides such as sodium chloride, potassium chloride, magnesium chloride, calcium chloride, and sodium bromide, and phosphates such as sodium dihydrogen phosphate and potassium dihydrogen phosphate. Further, the concentration of the above-mentioned inorganic salts is usually 0.1 to 10% by weight, preferably 0.5% by weight.
~5% by weight.

Furthermore, the halogen-based oxidizing agent used in the present invention is
At least one selected from sodium hypochlorite, bromine, iodine, and chlorine dioxide, and its concentration is 1 to 11.
00 ppm, preferably 10-70 ppm.

The types of these inorganic salts and halogen-based oxidizing agents are selected based on the membrane material, so that when the selectively permeable membrane on which polypeptide is deposited is treated with the aqueous solution, the membrane performance, especially the water permeation rate, is maximized. It is best to select it experimentally depending on the structure, properties of the polypeptide, etc.

Generally, a combination of sodium hypochlorite and a neutral sulfate is preferred.

The treatment of a membrane with an aqueous solution containing an inorganic salt and a halogen-based oxidizing agent as described above is preferably carried out by circulating and supplying this aqueous solution to the membrane surface under pressure.

Although the treatment temperature is not particularly limited, it is usually 5~
The temperature is selected to be 80°C, preferably 20 to 50°C, and lower than the heat resistance temperature of the target film. However, depending on the material of the film, it is of course possible to process at a high temperature exceeding the above range. Although the treatment time depends on the properties of the polypeptide and the type and concentration of the inorganic salt and oxidizing agent used, it is generally 10 minutes to several days, preferably 0°5 to 5 hours. Other methods of regeneration treatment include a method in which the membrane is immersed in an aqueous inorganic salt solution and a method in which the membrane is allowed to stand still, a method in which an aqueous solution is permeated under pressure, and the like.

The shape of the membrane treated by the method of the present invention is not limited in any way, and may be any shape such as a flat plate, a tube, a spiral, and a hollow fiber. Further, in order to enhance the cleaning and regeneration effect of the membrane, physical cleaning such as stirring, friction, ultrasonic cleaning, etc. may be used in combination depending on the membrane form.

According to the method of the present invention, a selectively permeable membrane in which polypeptides have been deposited on the membrane surface and membrane performance, particularly water permeability, has decreased, is treated with an alkali metal and/or alkaline earth metal salt and a halogen-based oxidizing agent. By washing with an aqueous solution containing the polypeptide, the polypeptide is specifically removed from the membrane surface, and thus the membrane recovers almost its initial performance and there is no fear of alteration or deterioration of the membrane. Although it is not necessarily clear why polypeptides are specifically removed by treating the membrane with an aqueous solution containing an inorganic salt in combination with a halogen oxidizing agent, the oxidizing effect of the halogen oxidizing agent as well as the inorganic salt This metal ion probably has some effect on the desorption of the polypeptide from the membrane.

The present invention will be explained below with reference to Examples, but the present invention is not limited to these Examples in any way.

Example 1 A reverse osmosis membrane made of cellulose acetate was attached to a flow cell to prepare an experimental module. When the fermentation extract was continuously supplied to this membrane module at room temperature and a pressure of 40 kg/cd for 100 hours, the water permeation rate was 0.70 rrr10
0.2 On from f day? /r+(・Decreased daily.

Therefore, an aqueous solution containing 2% by weight of sodium sulfate and 10 ppm of sodium hypochlorite was heated at a temperature of 25°C and a pressure of 3 kg/cII! When circulating water was supplied to the above membrane for 1 hour under the above conditions, the water permeation amount was 0°65r under the same conditions as above.
It recovered to rr/m day (times (summer rate 93%)).

Example 2 The membrane after continuous operation was treated in exactly the same manner as in Example 1 except that 30 ppm of iodine was used instead of sodium hypochlorite, and the amount of water permeated through the membrane was 0. Recovered in 50 rd/m day (recovery rate 71%)
).

Example 3 Polyhinyl alcohol and ethylenediamine were crosslinked with trimesic acid chloride on a polysulfone membrane prepared according to the method described in JP-A-5'1-27102 to obtain a selective composite permeable membrane. , modularized.

This membrane module feeds animal protein-containing wastewater at
When the water was continuously supplied for 100 hours at a pressure of 30 kg/c-, the water permeation rate was 1.5 n? /rd·day to 0.63 rrr/g·day.

Therefore, an aqueous solution containing 2% by weight of magnesium sulfate and 30 ppm of sodium hypochlorite was prepared at a temperature of 30°C and a pressure of 3 kg/cn! When it was circulated and supplied to the above membrane for 1 hour under the above conditions, the water permeation amount was 1.4rI? under the same conditions as above.
The patient recovered in 1/m day (recovery rate 93%).

Comparative Example In Example 3, when the membrane was treated with a water-soluble solution containing only sodium hypochlorite without using magnesium sulfate, the water permeation rate recovered only to 0.93 m/rrr. rate 62%).

Claims (5)

[Claims] (1) A selectively permeable membrane on which a polypeptide is deposited is treated with an aqueous solution containing at least one selected from alkali metal salts and alkaline earth metal salts and a halogen-based oxidizing agent. A method for regenerating a selectively permeable membrane. (2) The method for regenerating a selectively permeable membrane according to claim 1, wherein the metal salt is a sulfate and/or a hydrochloride. (3) The method for regenerating a selectively permeable membrane according to claim 1, wherein the halogen-based oxidizing agent is at least one selected from sodium hypochlorite, bromine, iodine, and chlorine dioxide. (4) The method for regenerating a selectively permeable membrane according to claim 1, wherein the concentration of the inorganic salt is 0.1 to 10% by weight. (5) The method for regenerating a selectively permeable membrane according to claim 1, wherein the concentration of the halogen-based oxidizing agent is 1 to 1100 pp.