JPS63278506A - Addition of disinfectant property to porous organic hollow filament membrane - Google Patents

Abstract

PURPOSE:To add disinfection property to hollow filament membrane in a filtration module by plating the pore surface of porous hollow filaments by successively running an aq. acid soln. contg. Sn<2+> ion, aq. acid soln. contg. Pd<2+> ion and silver plating soln. through the hollow filaments. CONSTITUTION:In a filtration module which is made by putting porous polyethylene hollow filament membrane, etc., in a housing, and burying and fixing its opening end with urethane resin, etc., a hydrochloric acid soln. of tin (II) chloride is filtered with the module, after the hollow filament membrane in the module is made hydrophilic. The hollow filament membrane is washed with deionized water, and thereafter a hydrochloric acid soln. of palladium chloride is run through the hollow filaments and again the filament membrane is washed with deionized water. Then, the plating soln. contg. silver ion such as silver nitrate, etc., complexing agent such as ethylenediamine, etc., and reducing agent such as potassium sodium tartrate, is run through the hollow filaments. Thereby, an electroless plated hollow filament membrane is obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Field of Application): The present invention relates to a method for imparting bactericidal properties to porous organic hollow fiber membranes.

(Prior Art) In recent years, the demand for clean water has spread over a wide range of fields, including cutting-edge industrial fields such as ultra-LSI manufacturing, medical fields such as hospitals, and general process fields such as drinking water.

As a water purification method, especially when the purpose is to remove bacteria, a method of filtering with a membrane capable of inhibiting bacteria, or a combination of this with activated carbon, an ion exchange method, etc. is widely adopted. In particular, porous polyolefin hollow fiber membranes are attracting attention because they inhibit bacteria and can easily obtain relatively high water permeability.

(Problem to be solved by the invention) However, when water containing bacteria is filtered using a membrane that inhibits bacteria, although the membrane inhibits bacteria, the inner body of the membrane does not have bactericidal properties. Bacteria may accumulate on the upstream side of the pipe, causing problems such as the bacteria multiplying there and the generation of bad odors due to bacterial metabolites.

In order to prevent this, methods such as using silver-coated activated carbon as activated carbon or irradiating with an ultraviolet lamp to sterilize the inside of the faA module have been taken.

However, although silver coated activated carbon is effective to some extent, it only has a bactericidal effect on the water that comes into contact with or near the silver coated activated carbon, and has a relatively weak bactericidal effect on the water metal bodies that are filtered, meaning that bacteria may remain. , bacteria may grow on the membrane surface.

Furthermore, those using an ultraviolet lamp must keep the lamp on at all times, which not only poses problems in terms of economy and operability, but also causes eye damage if the ultraviolet rays hit the eyes.

The present invention was made in view of this situation, and an object of the present invention is to provide a method for easily imparting bactericidal properties to porous organic hollow fiber membranes.

(Means for Solving Problems) That is, the gist of the present invention is to house in a housing a porous organic hollow fiber membrane having micropores in which the micropores communicate from the outer wall surface to the inner wall surface, and to A filtration module is created by fixing the ends in a liquid-tight manner to the housing, and an acidic aqueous solution containing divalent tin ions is applied from one side of the hollow fiber membrane to the other, followed by an acidic aqueous solution containing only a few palladium ions. ,
Next, there is a method for imparting bactericidal properties to porous organic hollow fibers, which comprises sequentially filtering a silver plating solution containing silver ions, a complex forming agent, and a reducing agent.

In the present invention, ultrafiltration membranes, microfiltration membranes, etc. are preferably used as the hollow fiber membranes to be treated, and any material can be used as the material, including cellulose-based,
Polycarbonate-based, polysulfone-based, polyimide-based,
Examples include polyamide-based, polyvinyl alcohol-based, polyolefin-based, etc. Among these, polyolefin hollow fibers made porous by melt-spinning and stretching have a high water permeability among membranes that can inhibit bacteria. This method is preferably used because it does not require additives and therefore there is little possibility that the film will contain impurities.

The filtration module using hollow fiber membranes may be of any shape as long as it is normally used for filtration.
Hollow fibers are made into a U-shape and housed in a housing, the open end is fixed liquid-tight with botting resin, and the inside and outside of the hollow fiber membrane are isolated using botting resin.The hollow fiber membrane bundle is arranged in a straight line. An example is one in which the opening end is fixed and housed in a housing.

The module housing material is not particularly limited as long as it is not altered by an acidic aqueous solution or a silver plating solution, but resins such as polyvinyl chloride, acrylic resin, and polycarbonate are preferably used. As the potting resin, polyurethane, epoxy resin, etc. can be used.

If the hollow fiber membrane is wood-philic, it may be subjected to electroless plating treatment after being made into a module, but if it is hydrophobic, the membrane is made hydrophilic before or after being made into a module. This tree parenting treatment may be temporary or permanent. In the case of temporary hydrophilization, it is necessary to keep it soaked in water after the hydrophilization treatment or to make it hydrophilic each time it is filtered, but there is little risk of contamination with impurities. In the case of permanent hydrophilization, drying can be performed afterwards. Temporary hydrophilization can be achieved by filtering a water-miscible organic solvent such as alcohol or an aqueous surfactant solution, and then replacing and washing these liquids with water. Permanent hydrophilization can be achieved by grafting lignophilic molecules or by coating the surface with a hydrophilic polymer and crosslinking it.

In the present invention, electroless plating is performed after assembly into a module. As the electroless plating method, any method that can perform electroless silver plating can be adopted, but for example, the following method can be used.

That is, first, a sensitization treatment for electrolytic plating is performed by passing an acidic aqueous solution containing divalent tin ions through the hollow fiber membrane. As the divalent tin ion, stannous chloride is preferably used, and hydrochloric acid can be used to make the aqueous solution of stannous chloride acidic. It is preferable that the concentration of stannous chloride is about 10 to 30 g/It, and the concentration of hydrochloric acid is about 20 to 60 g/It. Other components can be added to this aqueous solution as long as they do not impair the sensitization described above, such as surfactants and the like. The liquid passage time, that is, the contact time between the membrane and the aqueous solution varies depending on the temperature, and is preferably 4 to 5 minutes or more when the temperature is room temperature. Next, after thoroughly washing and removing the tin ion aqueous solution inside the module with deionized water, an acidic aqueous solution containing a divalent palladium solution is passed through the module to activate the hollow membrane.

The conditions for this activation treatment may be the same as those used in ordinary electroless plating, for example,
Palladium chloride can be used as the palladium ion, and the concentration of palladium chloride is 0.1 to 0. 5g/
Preferably it is It.

It is preferable to use hydrochloric acid at 1 to 5 mA/j2 for acidifying the aqueous solution. The contact time between the acidic palladium aqueous solution and the hollow fiber membrane is preferably 4 to 5 minutes or more at room temperature. After this treatment, the inside of the module is thoroughly cleaned again using deionized water, and then silver plating treatment is performed.

Silver plating treatment is performed by passing a silver plating solution containing silver ions, a complex forming agent, and a reducing agent through the hollow fiber membrane. Any water-soluble silver salt can be used as the silver salt that provides silver ions, but silver nitrate is usually used. The concentration of silver may be appropriately set in consideration of the desired amount of silver deposited, plating conditions, etc. Any compound that forms a stable complex ion with silver can be used as the complex forming agent, and preferred examples include ammonia and various amines. The molar ratio of complexing agent to silver must be at least 1 times.

Since the standard unipolar potential of silver ions is extremely high at +81V, a reducing agent with weak reducing power is sufficient, and usually glucose,
Rochelle salt, formalin, etc. are used.

The contact time between the silver plating solution and the hollow fiber membrane may be appropriately set in consideration of the desired amount of silver deposited and the like.

Note that it is preferable that the permeation rate of the silver plating solution through the hollow fiber membrane be relatively slow in order to obtain a good plating state.

(Example) The present invention will be explained in more detail below using Examples.

Example 1 A bundle of porous polyethylene hollow fiber membranes (inner diameter 275 μm, porosity 70%, trade name EHF, manufactured by Mitsubishi Rayoshi) was placed in a U-shaped transparent polyvinyl chloride pipe with an inner diameter of 9 cm and a length of 10 cm. The open end is embedded and fixed in polyurethane resin, and the membrane area is 960rr? module. For this module, 100 mJ of ethanol was applied from the outer wall of the hollow fiber membrane to the inner wall at room temperature! 20mJl/min
The hollow fiber membrane was made hydrophilic by flowing at a speed of . Next, after thoroughly washing the inside of the module with deionized water and replacing ethanol with the water, 50 mJ2 of a stannous hydrochloric acid solution containing 20 g/λ of stannous chloride and 20 mf/2 of hydrochloric acid was applied to this hollow fiber membrane module. Filter and soak the hollow fiber membrane in 200mj of deionized water.
Wash with Z and then palladium hydrochloric acid aqueous solution 5 containing 0.2 g/A of palladium chloride and 2.5 m JZ/JZ of hydrochloric acid.
The solution was passed through 0 mJZ and washed again with 200 ml of deionized water. The treatment time for each treatment liquid was 5 minutes. Next, as a silver plating bath, silver nitrate 0. -5g/u,
A solution in which 3.2 g/fl of ethylenediamine and 9.8 g/IL of sodium tartrate were dissolved was used, and the solution was passed through the solution at a flow rate of 2 mfl/min and 50 mJZ. The electroless silver-plated hollow fiber membrane module thus obtained was thoroughly washed with deionized water. Tap water treated with activated carbon was passed through this module for 8 hours a day for 10 days so as to flow from the inside to the outside of the hollow fiber membrane, and then the module was left at room temperature for 10 days without draining the water inside the module. After that, the water flow test was performed again, but no bad odor was detected in the filtered water.

Moreover, the amount of water permeation after restarting the fluid flow was approximately the same as the initial amount of water permeation. In addition, when one of the modules electrolessly plated with silver was similarly disassembled and the hollow fiber membrane was taken out, observation using a scanning electron microscope and an X-ray microanalyzer revealed that not only the inner and outer wall surfaces of the hollow fibers but also the inner and outer walls of the hollow fibers were observed. , Silver was also attached to the surface of the micropores of the hollow fiber membrane.

For comparison, we prepared a module that was not subjected to electroless silver plating treatment (a series of treatments of stannic acidic aqueous solution treatment, palladium hydrochloride acidic aqueous solution treatment, and silver plating treatment), and subjected it to the same water flow treatment as above. However, a foul odor was felt from the initial filtrate after water flow was restarted, and the amount of water permeated after restarting was as small as about 80% of the initial amount of water permeated.

This shows that the porous hollow fiber membrane subjected to the method of imparting bactericidal properties of the present invention has excellent effects.

(Effects of the Invention) The method for imparting bactericidal properties of the present invention enables silver plating not only to the inner and outer wall surfaces of the porous hollow fiber membrane but also to the surface of the micropores, and moreover, does not reduce the water permeability of the hollow fiber membrane. Has characteristics.

In filtration using hollow fiber membranes that inhibit bacteria, there is a problem that bacteria accumulate on the upstream side of the packing and multiply there, and when used in combination with silver-coated activated carbon, the contact efficiency between the activated carbon and water is low, so it is not sufficient. However, when the pore surface is plated with silver, bacteria in the filtered water are attracted to the pore surface along with the filtered water, which increases the sterilization effect. have

In the present invention, as an electroless silver plating method, silver can be attached to the micropore surface of a porous hollow fiber membrane for the first time by adopting a method in which each treatment solution is sequentially filtered through a porous hollow fiber membrane. It is a simple thing. conventional vapor deposition method,
Although it is possible to attach silver to the inner and outer surfaces of the hollow fiber membrane using the silver plating method, it is difficult to attach silver to the surface of the micropores, and if you try to coat the micropores with silver, you have no choice but to collapse the micropores. Although the method of the present invention has such drawbacks, it is an excellent method that can reliably plate the surface of micropores with silver.

Claims (1)

[Claims] 1) A porous organic hollow fiber membrane having micropores in which micropores communicate from the outer wall surface to the inner wall surface is housed in a housing, and its open end is fixed to the housing in a liquid-tight manner to create a filtration module, From one side of the hollow fiber membrane to the other, an acidic aqueous solution containing divalent tin ions, then an acidic aqueous solution containing divalent palladium ions, and then a silver plating solution containing silver ions, a complex forming agent, and a reducing agent. A method for imparting bactericidal properties to a porous organic hollow fiber membrane, which sequentially filters the following substances.