JPH09117763A - Treatment of waste water from chemical/mechanical polishing - Google Patents

Abstract

PROBLEM TO BE SOLVED: To lessen the deterioration of a high polymer porous membrane and to reuse filtered water when treating CPM waste water using the high polymer porous membrane filter by decomposing hydrogen peroxide in waste water in advance and feeding the waste water to the filter. SOLUTION: From a chemical/mechanical polishing (CPM) device 1, CPM waste water containing hydrogen peroxide and alumina abrasive grains is discharged to a pretreating tank 2. NaOH aqueous solution in a neutralizer tank 3 is injected by an injection pump 8 and hydrogen peroxide decomposing enzyme in a hydrogen peroxide decomposing agent tank 4 is injected by a fixed delivery injection pump 9, and the mixture is agitated by an agitator 6. The treated liquid in which hydrogen peroxide is thus decomposed in the pretreatment tank 2 is transferred to a circulation tank through liquid transfer piping 11 by a liquid transfer pump 10, and enters a high polymer membrane through a circulating pump, and is separated into filtrate and concentrate there. The filtrate is used as washing water through an ion exchange tower.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for treating wastewater (hereinafter also referred to as CMP wastewater) discharged from a chemical mechanical polishing (hereinafter referred to as CMP) device. More specifically, the hydrogen peroxide in the CMP waste water is decomposed by a hydrogen peroxide-decomposing enzyme in the pretreatment device, and then filtered using a polymer porous membrane filtration device to obtain reusable filtered water and inorganic abrasive particles. The present invention relates to a method of separating and processing concentrated water containing the same.

[0002]

_2. Description of the Related Art Acid-based slurry wastewater discharged from a CMP apparatus contains SiO ₂ or Al having a size of 0.01 to 3 μm.
Inorganic abrasive grains such as ₂ O ₃ or MgO and H ₂ SO ₄ or HF
It cannot be discharged as it is because it contains inorganic acids such as and hydrogen peroxide and both are suspended.

Previously, the present inventors have proposed a method for regenerating this wastewater using a porous membrane. As a result of further study, an inorganic type porous membrane is used as the porous membrane in terms of treatment cost, space for treatment equipment and the like. Although the polymer porous membrane is superior to that of the porous membrane, it has become clear that the polymer porous membrane is deteriorated in the case of the acid-based slurry wastewater containing hydrogen peroxide.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to solve the problems of the CMP wastewater treatment method using a polymer porous membrane filtration device, that is, to reduce the deterioration of the polymer porous membrane and to filter it. It is to provide a method for treating CMP wastewater in which water can be reused.

[0005]

As a result of earnest studies, the present inventors have found that the above problems can be solved by decomposing hydrogen peroxide in CMP wastewater with a hydrogen peroxide decomposing agent. The present invention has been completed. That is, the present invention is C
When treating MP wastewater using a polymer porous membrane filtration device, hydrogen peroxide in the wastewater is decomposed in advance by a pretreatment device and supplied to the filtration device.
It is a wastewater treatment method, and when the hydrogen peroxide in the CMP wastewater is decomposed in advance by a pretreatment device, p
A method for treating CMP wastewater, which comprises injecting a hydrogen peroxide-decomposing enzyme after neutralizing H.

In the present invention, the pretreatment device is a pH meter,
It consists of a pretreatment tank with a stirrer, a liquid level meter, and a liquid feed pump, a hydrogen peroxide decomposer tank with a metering injection pump, and a neutralizer tank with an injection pump. Controller (hereinafter,
Call it a sequence). The size of the pretreatment tank, the size of the circulation tank of the polymer porous membrane filtration device that separates the concentrated water and the treated water, and the feed rate are the discharge rate of CMP wastewater and the retention required for decomposition of hydrogen peroxide. It is good to decide in consideration of time. 10 for hydrogen peroxide degrading enzyme
The retention time is preferably 30 minutes.

The hydrogen peroxide decomposing agent used in the present invention is an inorganic salt such as sulfurous acid, phosphorous acid, oxalic acid, permanganic acid, thiosulfuric acid and ferrous iron, or a hydrogen peroxide decomposing enzyme. Degradative enzymes are preferred. The inorganic salt may be added in an amount equal to the specified concentration of hydrogen peroxide. In the case of hydrogen peroxide-degrading enzyme, 1/10 of hydrogen peroxide mass concentration
The concentration may be 0 or higher, preferably 1/30 or higher.

In the present invention, when a hydrogen peroxide-decomposing enzyme is used as a hydrogen peroxide-decomposing agent, a neutralizing agent is used to neutralize the pH of CMP wastewater in order to increase the decomposition rate of hydrogen peroxide. Is preferred. As a neutralizing agent, KOH,
Alkaline aqueous solutions such as NaOH, Ca (OH) ₂ and NH ₄ OH are preferable. CM using any of the neutralizing agents
The pH of the P waste water is adjusted to 5 to 11, preferably 6 to 8.

In the present invention, the neutralizing agent and the hydrogen peroxide-decomposing enzyme may be added in any order, but it is more preferable to add the neutralizing agent first. In the present invention,
The CMP wastewater in which hydrogen peroxide has been decomposed in the pretreatment device is fed to the polymer porous membrane filtration device by the liquid feed pump of the pretreatment tank. The polymer porous membrane filtration device used in the present invention is
Circulation tank with liquid level meter, filtrate tank, and concentrate tank, circulation pump and backwash pump, polymer porous membrane, integrated flow meter, integrated flow indicator, flow meter, pressure transmitter, pressure gauge, It consists of a thermometer, turbidity detector, turbidity meter, conductivity meter, pH meter, automatic valve, and ion exchange resin tower and control panel, and is sequence-controlled, but it is not necessary to have all the above-mentioned instruments. It is good to prepare according to the purpose. There are no restrictions on the material and shape of the tank. The pump is also not particularly limited, but it is preferable to select one having a structure in which the seal portion is not easily damaged by the abrasive grains in the waste water.

The polymer porous membrane used for separation in the present invention is
20 to 500 angstrom UF membrane (ultrafiltration membrane)
Also, it is preferable to use a film having a pore size smaller than the size of the abrasive grains from the film called MF film (microfiltration film) having a thickness of 0.05 to 1 μm. Further, when the hydrogen peroxide-decomposing enzyme is also desired to be concentrated and removed, a UF membrane may be used. As the material of the polymer porous film, polyacrylonitrile, polysulfone, polyethylene, polypropylene, polyvinylidene fluoride,
Examples thereof include polytetrafluoroethylene, cellulose acetate, polyamide, polyvinylidene chloride, and polyether sulfone. The shape of the membrane is tubular membrane, flat membrane,
Any shape such as a spiral membrane or a hollow fiber membrane may be selected.

In the wastewater treatment method using the porous polymer membrane filtration device of the present invention, a method of flowing filtered water so as to be orthogonal to the membrane filtration surface and a method of flowing filtered water parallel to the membrane filtration surface (cross flow) Method is known, but the cross-flow method is preferable. The operating pressure may be set to an optimum value in consideration of the pressure resistance of the membrane, the filtration rate and the filtration stability. The circulation flow rate is preferably high, and the flow rate may be 1 to 3 m / sec.

The liquid obtained by filtering the set amount of filtrate with the polymer porous membrane used in the present invention and concentrating it to the desired concentration is discharged to the concentrated liquid tank by the circulation pump. On the other hand, the filtered water is passed through an ion exchange resin tower composed of a cation resin and an anion resin to remove ionic substances. Needless to say, an exchange resin tower is not required when the removal of ionic substances is not required.

The quality of the filtered water of the polymer porous membrane used in the present invention may be monitored by installing a turbidity detector, a turbidity meter, an electric conductivity meter, a pH meter and the like, if necessary.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention and comparative examples will be specifically described below with reference to the drawings.

[0015]

EXAMPLE 1 FIG. 1 is a schematic flow chart of an apparatus for pretreatment of CMP wastewater, in which 1 is a CMP apparatus, 2 is a pretreatment tank, 3 is a neutralizer tank, and 4 is hydrogen peroxide decomposition. Agent tank, 5 liquid level meter, 6 stirrer, 7 pH meter, 8 neutralizer injection pump, 9 hydrogen peroxide decomposer injection pump,
Reference numeral 10 is a liquid feed pump, and 11 is a liquid feed pipe for feeding the pretreated CMP wastewater to the polymer porous membrane filtration device of FIG. FIG. 2 shows a polymer porous membrane filtration device for treating pretreated CMP wastewater, 12 is a liquid level meter, 13 is an integrating flowmeter and a flow sensor, 14 is a polymer porous membrane, and 15 is ion exchange. A column, 16 is a circulation pump, 17 is a circulation tank, and a concentrate tank. Both devices are devices that operate under sequence control.

The hydrogen peroxide concentration was measured by the potassium permanganate titration method. From the CMP apparatus 1, 100 liters of CMP wastewater containing hydrogen peroxide and alumina abrasive grains was discharged to the pretreatment tank 2. CMP wastewater is cloudy and has a pH
4.0, electric conductivity (hereinafter referred to as EC) 240 μs / c
m and hydrogen peroxide concentration were 1500 mg / liter.

The stirrer 6 rotates, and 1 in the neutralizer tank 3 is rotated.
% NaOH aqueous solution was injected into the pretreatment tank via the injection pump 8. The amount was added by receiving an electric signal from the pH meter 7 and performing sequence control so that the infusion pump operates until the reading of the pH meter reaches 7. Next, a fixed amount of hydrogen peroxide decomposing enzyme in the hydrogen peroxide decomposing agent tank 4 was sent to the pretreatment tank by the constant volume injection pump 9. As the hydrogen peroxide-degrading enzyme, Enchilon OL-50 manufactured by Rakuto Kasei Kogyo Co., Ltd. was used, and 7.5 g corresponding to 1/20 the mass of hydrogen peroxide in 100 liters of CMP wastewater was added. Hydrogen peroxide concentration after stirring for 10 minutes is 45 mg
/ Liter, and the decomposition rate of hydrogen peroxide was 97%.

The liquid of the pretreatment tank in which hydrogen peroxide was decomposed was sent to the circulation tank 17 of FIG. 2 through the liquid sending pipe by the liquid sending pump. The fed liquid entered the porous polymer membrane 14 through the circulation pump 16, and was separated into a filtrate and a concentrated liquid there. The concentrated liquid was returned to the circulation tank 17, and the filtrate was passed through the integrated flow meter and the flow sensor 13 and passed through the ion exchange tower.

The polymer porous overmembrane 14 is an ultrafiltration membrane manufactured by Asahi Kasei Corporation, ACV-3050 (polyacrylonitrile membrane, membrane area 3.1 m ² , hollow fiber inner diameter 1.4 mm).
Was used. The filtration was carried out by a cross-flow method at a filtration temperature of 30 ° C., an operation average pressure of 100 KPa, a flow rate in the membrane channel of 2 m / sec, and a filtration rate of 1.1 liter / min and m ² .

The filtered water is colorless and transparent, pH 7.1, EC3
μs / cm, which was used as washing water. The retention of tensile strength of the film after operating for 6 months was 90%.

[0021]

Comparative Example 1 The CMP wastewater obtained in Example 1 was separated without pretreatment in a polymer porous membrane filtration device using the ultrafiltration membrane ACV-3050 used in Example 1. The operating conditions of the filtration device were the same as in Example 1. The filtered water did not pass through the ion exchange tower. Hydrogen peroxide concentration of filtered water is 145
0 mg / liter, pH 4.0, EC 180μ
The water quality was not reusable or discharged at s / cm.
The retention rate of tensile strength of the film after operating for 6 months was 46%.

[0022]

According to the present invention, since the CMP wastewater containing acid-type hydrogen peroxide is treated by the pretreatment device and concentrated by the polymer porous membrane filtration device, deterioration of the polymer porous membrane is reduced. ,
Longer membrane life. Further, the filtered water meets the water quality standards for washing water, industrial water, cooling water, sprinkling water, and agricultural water, and thus can be used for these applications.

[Brief description of the drawings]

FIG. 1 is a schematic flow chart of a pretreatment device of a CMP wastewater treatment device of the present invention.

FIG. 2 is a schematic flow diagram of a polymer porous membrane concentrating device of the CMP wastewater treatment device of the present invention.

[Explanation of symbols]

 1 CMP device 2 Pretreatment tank 3 Neutralizer tank 4 Hydrogen peroxide decomposer tank 5 Liquid level meter 6 Stirrer 7 pH meter 8 Neutralizer injection pump 9 Constant injection pump 10 Liquid feed pump 11 Liquid feed pipe 12 Liquid level Level meter 13 Integrated filtrate flow meter and flow sensor 14 Polymeric porous membrane 15 Ion exchange tower 16 Circulation pump 17 Circulation tank 18 Concentrated liquid tank

Claims (2)

[Claims] 1. When treating a chemical mechanical polishing wastewater using a polymer porous membrane filtration device, hydrogen peroxide in the wastewater is decomposed in advance by a pretreatment device and supplied to the filtration device. Chemical mechanical polishing wastewater treatment method. 2. When pre-decomposing hydrogen peroxide in a chemical mechanical polishing wastewater by a pretreatment device, the pH of the wastewater is neutralized, and then a hydrogen peroxide-decomposing enzyme is injected. The chemical mechanical polishing wastewater treatment method described.