JPH08243559A - Hollow fiber membrane filtration method - Google Patents

Abstract

(57) [Summary] [Object] The present invention aims to remove inorganic ions dissolved in water. [Structure] The present invention is directed to the metal ion dissolved in raw water,
After oxidization and solidification precipitation, suction type hollow fiber membrane module
The present invention relates to a hollow fiber membrane filtration method characterized in that it is filtered with a filter.

Description

Detailed Description of the Invention

[0001]

INDUSTRIAL APPLICABILITY The present invention is effective in a field where a large amount of industrial water such as fiber treatment, cleaning, food industry, or water supply is used, and water containing as little metal ion as possible is used. Hollow fiber membrane filtration method.

[0002]

2. Description of the Related Art Conventionally, sand filtration has been typically used as a filtration method for removing iron rust and suspended matter in water.

Suspending substances that do not settle in solution (silica,
Iron and its compound particles, calcium and magnesium compound particles) with a polyethylene hollow fiber membrane having a porous structure (JP-A-58-109111).
Is proposed.

In addition, the pH of the water to be treated is adjusted by using a porous membrane having a chelate group in its side chain that binds to heavy metal ions in water (iron, copper, cobalt, nickel, etc.) to remove heavy metal ions in water. It has been proposed to remove it (JP-A-3-21390).

However, according to these methods, the filtration accuracy is insufficient, and it is practically difficult to produce a membrane having a chelate group in the side chain, and the metal is not used on an industrial scale. It was not possible to remove the ions.

In addition to the above, in order to remove manganese ions, a method of passing manganese sand is known, but a large amount of water is required for backwashing and its treatment is required.

[0007] For example, industrial water is generally used as the water used in the process water of the dyeing factory, including the fiber manufacturing process, but it contains several ppm of iron ions and manganese ions. After the product becomes a product, it is oxidized by air and the fiber product becomes dark or yellow,
In general, it is desirable that metal ions, especially iron ions and manganese ions, are not included as much as possible in order to develop color due to reaction with chlorine.
It is required to reduce to below ppm.

When it is necessary to remove metal ions as impurities contained in industrial water with high efficiency as described above, a filtration method using a reverse osmosis membrane is used in the general water treatment field. . However, when a reverse osmosis membrane is used, the pressure required for filtration tends to be very high, and the cost of water production is still high, making it unsuitable as a filtration method in the fiber manufacturing process and dyeing process. is there.

Further, there is a method of using an ion exchange resin, but it is known that manganese, silicon, etc. are deposited and adhered to the surface of the resin to remarkably reduce the ion exchange ability, and regeneration is also difficult.

[0010]

An object of the present invention is to provide a filtration method suitable for treating a large amount of water containing a relatively large amount of metal ions.

[0011]

Means and Actions for Solving the Problems Such an object is achieved by the following inventions. That is, the gist of the present invention resides in a hollow fiber membrane filtration method, which comprises oxidizing metal ions dissolved in raw water to solidify and precipitate them, and then filtering with a suction type hollow fiber membrane module.

In order to oxidize and precipitate metal ions dissolved in water by solidification, for example, air or ozone is blown into raw water containing iron ions, manganese ions, or an oxidizing agent such as chlorine is injected. Is achieved by carrying out an oxidation treatment. In the present invention, a reactor that performs such an oxidation treatment is called an oxidizer.

Taking water purification treatment of river water as an example, air is inexpensive, but since the reaction rate with iron and manganese is slow, PH is increased within the allowable range and the reaction time is 15 minutes or more. It is necessary to.

In the case of ozone, 2 to 5 mg of ozone is injected per liter of raw water, and in the case of chlorine, 2 to 5 mg of chlorine is injected per liter of raw water so that residual chlorine is present in an amount of 0.2 mg or more.

Oxidation-treated water containing oxides solidified and precipitated by the oxidation treatment is filtered by suction with a suction type hollow fiber membrane module.
In the present invention, the use of the suction type hollow fiber membrane module is essential, and the external pressure type hollow fiber membrane module has the following drawbacks. In other words, since the precipitated oxide particles are small, there is a risk of irreversible blockage on the membrane, and a large amount of circulation is required to obtain the membrane surface velocity, and power is also required for pressurization. It becomes less efficient.

The suction type hollow fiber membrane module of the present invention may be, for example, a cylindrical type in which hollow fiber membranes are concentrically arranged in a circular shape or concentric circles which have been used in the field of conventional microfiltration. Although it does not matter, for example, JP-A-5-22035
A hollow fiber membrane module as disclosed in Japanese Patent No. 6 is preferably used in which the shape of the open end of the hollow fiber membrane is an elongated rectangular shape.

In the case of suction filtration with such a module, the hollow fiber membrane is fixed in the oxidation-treated water in a vertical state or a horizontal state, but particles adhere to the hollow fiber membrane module. A vertical state is desirable to prevent this.

In the suction filtration, by adopting a so-called intermittent suction operation method in which temporary suction is periodically stopped, deposits on the film surface can be efficiently prevented from entering the inside of the film surface.

During suction filtration, the membrane surface is washed intermittently or continuously from the air diffuser by air scrubbing,
It is preferable to carry out filtration. By doing so, inorganic substances and the like are deposited on the surface of the hollow fiber membranes as in the conventional cylindrical type microfiltration module, and the hollow fiber membranes are fixed and integrated, the effective membrane area is reduced, and the filtration flow rate is rapidly increased. Does not occur, and the recovery of membrane function is very easy.

As the hollow fiber membrane used in the present invention, those made of various materials such as cellulose type, polyolefin type, polyvinyl alcohol type, PMMA type and polysulfone type can be used. Here, considering the ease of processing into a knitted fabric, a material having a high strength and elongation such as polyethylene or polypropylene is preferable. This hollow fiber membrane is
Pore diameter 0.01-1 μm, porosity 20-90%, film thickness 5-
Those having a range of 300 μm and an outer diameter of 20 to 200 μm are preferable.

As a surface property of the hollow fiber membrane, a so-called permanent hydrophilization membrane having a hydrophilic group on the surface is desirable. As a method for producing a permanent hydrophilic membrane, a known method such as a method for producing a hollow fiber membrane with a hydrophilic polymer such as polyvinyl alcohol, or a method for hydrophilizing the surface of a hydrophobic polymer membrane can be used.

For example, when a hydrophilic polymer is applied to the surface of the membrane to make the hydrophobic hollow fiber membrane hydrophilic, examples of the hydrophilic polymer include:
Examples thereof include saponified products of ethylene-vinyl acetate copolymer (= ethylene-vinyl alcohol copolymer) and polyvinylpyrrolidone. Thus, when the hydrophilic polymer is coated on the hollow fiber membrane, it is possible to prevent the polyolefin hollow fiber membrane from undergoing oxidative deterioration when treated with an oxidizing agent such as chlorine or ozone. preferable.

FIG. 1 shows a flow chart suitable for carrying out the present invention.
It shows a sheet. Raw water containing inorganic ions is oxidized and solidified and precipitated in the oxidizer 1, and the oxidized water 4 is then suction-filtered by the suction-type hollow fiber membrane module 3 in the container 2 to take out filtered water, The precipitate 6 is discharged from the bottom of the container 2. At this time, it is effective to perform air bubbling with an air diffuser to oscillate the hollow fiber membrane to remove the inorganic oxide adhering to the membrane surface.

[0024]

The present invention will be described in detail with reference to the following examples. Example 1 An experiment was conducted according to the flow chart shown in FIG. As raw water, iron ion 0.5 mg / liter, manganese ion 0.
An aqueous solution containing 05 mg / liter was supplied to the oxidizer at a rate of 26 liters per minute, and 1 mg / liter of soda hypochlorite was supplied as effective chlorine, resulting in solidification and precipitation of inorganic oxides. Water was obtained.

A precision hollow fiber membrane filter (Stellapore manufactured by Mitsubishi Rayon Co., Ltd.) in which a polyethylene hollow fiber membrane having a pore diameter of 0.1 μm is spread in a screen form and fixed at both ends by continuously flowing oxidized water into the container. -L brand name) and suction filtration was performed using a suction type hollow fiber membrane module.

The hollow fiber membrane module has a suction pressure of 0.1 kg.
It operated under the condition of / cm ² . During operation, air bubbles were scrubbed from below to prevent inorganic oxides from sticking to the membrane surface.

Thus, filtered water containing no inorganic ions could be obtained. The iron ion concentration of the filtered water is 0.00
4 mg / liter, manganese ion is 0.004 mg / liter
It was liter.

[0028]

As described above, according to the present invention, high-quality filtered water can be obtained by a simple method and can be used in the fiber manufacturing process, especially in a small-scale dyeing factory or cleaning factory. There is a great contribution to practical use.

[Brief description of drawings]

FIG. 1 is a flow chart suitable for carrying out the present invention.
Here is an example.

[Description of sign]

 1 Oxidizer 2 Container 3 Suction-type hollow fiber membrane module 4 Oxidized water 5 Air diffuser 6 Precipitate

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Akio Tateishi 2-3-19 Kyobashi, Chuo-ku, Tokyo Inside Mitsubishi Rayon Co., Ltd.

Claims (2)

[Claims] 1. A method for filtering a hollow fiber membrane, which comprises oxidizing a metal ion dissolved in raw water by solidification and precipitation, and then filtering the metal ion with a suction type hollow fiber membrane module. 2. The method according to claim 1, wherein the metal ions are iron ions or manganese ions.