JP4066527B2 - Treatment of wastewater containing hydrogen peroxide and ammonia - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for efficiently treating wastewater containing hydrogen peroxide and ammonia discharged from a semiconductor factory or the like.
[0002]
[Prior art]
Wastewater containing hydrogen peroxide and ammonia is discharged from the semiconductor manufacturing process. Since the hydrogen peroxide in the wastewater is applied to COD _Mn , it must be decomposed. Ammonia also needs to be treated because it causes eutrophication of rivers, lakes, and seas.
[0003]
Conventionally, as a method of removing only ammonia in waste water, there is a method by biological treatment, but in the method by biological treatment, sludge is generated; maintenance is difficult; reaction rate is slow, and a large equipment installation area There are disadvantages such as;
[0004]
Hydrogen peroxide in the wastewater is decomposed by adding a chemical such as catalase. However, in this method, it is difficult to control the injection amount of the chemical and it is difficult to obtain a stable water quality.
[0005]
As a method of solving such problems and efficiently decomposing and removing hydrogen peroxide and ammonia in the wastewater simultaneously, the present applicant has previously proposed a method of decomposing both components using a noble metal-supported catalyst. (JP-A-5-269475).
[0006]
[Problems to be solved by the invention]
In the catalytic cracking method using a noble metal-supported catalyst disclosed in JP-A-5-269475, there is a problem that operation at high temperature and high pressure is required, and initial cost is high.
[0007]
The present invention solves such problems, and wastewater containing hydrogen peroxide and ammonia capable of safely and efficiently treating hydrogen peroxide and ammonia in waste water under relatively low temperature and low pressure operating conditions. It aims at providing the processing method of.
[0008]
[Means for Solving the Problems]
The method for treating wastewater containing hydrogen peroxide and ammonia according to the present invention comprises treating wastewater containing hydrogen peroxide and ammonia under conditions of a pressure at which the liquid phase can be maintained at 20 ° C. to less than 100 ° C. and below normal pressure. As an active ingredient of the catalyst, one or two selected from platinum, palladium, ruthenium, rhodium, indium, iridium, silver, gold, cobalt, copper, nickel and tungsten, and a water-insoluble or poorly water-soluble compound of these metals. more decomposing hydrogen peroxide of the exhaust water in contact with the catalyst supported on a carrier, after discharging the oxygen gas generated by the decomposition of hydrogen peroxide from the system, 20 ° C. or higher to 100 ° C. below and normal It is characterized by volatilizing and removing ammonia under the conditions below the pressure .
[0009]
In the method of the present invention, only hydrogen peroxide in the waste water is catalytically decomposed (2H ₂ O ₂ → 2H ₂ O + O ₂ ), so that the operating conditions of high temperature and high pressure are not required, the temperature is less than 100 ° C., the pressure Catalytic cracking can be performed under relatively low temperature and low pressure operating conditions such as normal pressure and below.
[0010]
Ammonia remaining in the waste water after decomposing and removing hydrogen peroxide can be easily removed by volatilization. Volatilized ammonia may be condensed, recovered, reused, or decomposed by catalytic air oxidation.
[0011]
In addition, when ammonia is volatilized prior to the catalytic decomposition of hydrogen peroxide to catalytically decompose only the hydrogen peroxide in the wastewater, oxygen gas is simultaneously generated due to the decomposition of hydrogen peroxide, resulting in a decrease in thermal efficiency. There are disadvantages such as the generation of an explosive gas mixture of oxygen gas and ammonia gas.
[0012]
According to the present invention, safe and efficient treatment can be performed by volatilizing and removing ammonia after catalytic decomposition and removal of hydrogen peroxide.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described in detail with reference to the drawings.
[0014]
FIG. 1 is a system diagram showing an embodiment of a method for treating waste water containing hydrogen peroxide and ammonia according to the present invention.
[0015]
Waste water (raw water) containing hydrogen peroxide (H ₂ O ₂ ) and ammonia (NH ₃ ) is first introduced into the hydrogen peroxide decomposition apparatus 1 to perform catalytic decomposition of hydrogen peroxide.
[0016]
As the catalytic cracking apparatus 1, it is preferable to use a fixed bed type reaction tower packed with a catalyst.
[0017]
In the present invention, as the catalyst, catalyst as medium an active ingredient, platinum, palladium, ruthenium, rhodium, indium, iridium, silver, gold, cobalt, copper, nickel and tungsten, as well as water-insoluble compounds or poorly soluble of these metals Specifically, one or two selected from oxides such as cobalt monoxide, cobalt peroxide, nickel monoxide, ruthenium dioxide, rhodium trioxide, palladium monoxide, iridium dioxide, cupric oxide, and tungsten dioxide. The thing which carry | supported seed | species or more on support | carriers, such as an alumina, activated carbon, a titanium oxide, a zirconia, a zeolite, and another synthetic resin, is also mentioned. The supported amount of the metal and / or the compound thereof in the supported catalyst is usually 0.05 to 25% by weight, preferably 0.5 to 10% by weight of the support weight. Such collateral lifting catalysts, spherical, pellet-like, cylindrical, spall shape, a honeycomb shape, may be used in various forms of powder, etc., grains responsible lifting catalysts to use in a fixed bed reactor tower The diameter is usually about 0.2 to 10 mm, particularly about 0.5 to 5 mm.
[0018]
In addition, although the conditions for passing through the fixed bed type reaction tower vary depending on the concentration of hydrogen peroxide in the waste water and the catalyst used, in the present invention, only hydrogen peroxide is decomposed without decomposing ammonia. Such relatively low temperature and low pressure conditions can be employed.
[0019]
[Liquid flow conditions]
Temperature: less than 100 ° C, preferably 20-90 ° C
Pressure: Normal pressure or less (any pressure that can maintain the liquid phase)
Flow rate: SV1 to 100 hr ⁻¹ , preferably 10 to 50 hr ⁻¹
Moreover, since the decomposition rate of hydrogen peroxide will become small when the pH of waste water is acidic less than 7, it is preferable that it is pH 7 or more, especially pH 7-13.
[0020]
In the hydrogen peroxide decomposition apparatus 1, hydrogen peroxide in the raw water is decomposed into water and oxygen, and oxygen gas is discharged out of the system.
[0021]
The treated water of the hydrogen peroxide decomposing apparatus 1 contains almost no hydrogen peroxide and ammonia remains, but in the present invention, this water is introduced into the ammonia volatilization tower 2 to volatilize the ammonia in the water. To remove.
[0022]
Any known method such as a stripping method or an evaporation method (including a distillation method) can be adopted as the method for removing ammonia by volatilization, but the operating conditions are a low temperature of less than 100 ° C. and normal pressure or less. The low-pressure conditions are preferably employed. Specifically, the following method can be employed.
[0023]
(i) Stripping with air, nitrogen gas or the like at a water temperature of 20 ° C. or more and a gas-liquid ratio (G / L) of 1000 to 5000 times.
(ii) Stripping with steam at a water temperature of 60 ° C. or higher with a steam volume / throughput ratio of 5 to 20%.
(iii) Distillation is performed at a water temperature of 60 ° C. or more with a steam amount / treatment amount ratio of 5 to 60% and a reflux ratio of 1 to 7.
[0024]
The treated water from which ammonia has been volatilized and removed in this manner is discharged out of the system.
[0025]
The volatilized ammonia gas can be condensed and recovered as necessary, and can be effectively used for wafer cleaning and the like.
[0026]
The ammonia gas may be decomposed and removed by catalytic air oxidative decomposition.
[0027]
As the catalyst used for the catalytic air oxidative decomposition, the same catalyst as the hydrogen peroxide decomposition catalyst (excluding activated carbon) can be used.
[0028]
【Example】
The present invention will be described more specifically with reference to the following examples.
[0029]
Example 1
A synthetic waste water of ammonia nitrogen: 1250 mg / L, hydrogen peroxide: 6000 mg / L, pH 10.5 was prepared, and this was used as raw water. First, a cobalt peroxide-supported zeolite catalyst (cobalt supported amount 2.5 wt%, average A column packed with 60 mL of particle size 2 mm) was passed under the following conditions.
[0030]
[Liquid flow conditions]
Temperature: 20 ° C
Pressure: Normal pressure Flow rate: 370 mL / hr (SV = 6 hr ⁻¹ )
The hydrogen peroxide concentration in the effluent was 2 mg / L or less, and the ammoniacal nitrogen concentration was 1200 mg / L.
[0031]
1000 mL of this effluent is put into a volatilization column in which an acrylic resin column having an inner diameter of 50 mm and a height of 1500 mm is filled with glass beads having a diameter of 3 mm, and air is blown from the lower part with a diffusion tube at a speed of 50 NL / min (G / L = 3000). Double) and treated for 1 hour (water temperature 60 ° C.). The concentration of ammoniacal nitrogen remaining in the treated water was 60 mg / L.
[0032]
On the other hand, the average concentration of ammonia in the volatile gas generated in the volatile treatment was 600 ppm (volume ratio).
[0033]
After this volatilized gas was heated to 330 ° C., an oxidation catalyst tower (a reaction tower in which a stainless steel reaction tower having an inner diameter of 50 mm was filled with 150 mL of 0.5 wt% platinum-supported γ-alumina oxidation catalyst) was used at a superficial velocity (SV) of 20000 hr. After aeration at ^-1 , a reduction catalyst tower (a reaction tower in which a stainless steel reaction tower having an inner diameter of 50 mm was filled with 500 mL of a vanadium-titania reduction catalyst) was aerated at a superficial velocity (SV) of 6000 hr- ¹ .
[0034]
The obtained treatment gas had an ammonia concentration of 1 ppm (volume ratio) or less and an NO _x concentration of 10 ppm (volume ratio) or less.
[0035]
Example 2
A synthetic waste water of ammonia nitrogen: 2000 mg / L, hydrogen peroxide: 6000 mg / L, SiO ₂ : 2 mg / L, pH 11.0 was prepared. Using this as raw water, first, 0.5 wt% platinum-supported titania catalyst ( The solution was passed through a column packed with 60 mL of an average particle size of 1.5 mm under the following conditions.
[0036]
[Liquid flow conditions]
Temperature: 60 ° C
Pressure: Normal pressure flow rate: 1200 mL / hr (SV = 30 hr ⁻¹ )
The hydrogen peroxide concentration in the effluent was 2 mg / L or less, and the ammoniacal nitrogen concentration was 1800 mg / L.
[0037]
1000 mL of this treatment liquid was concentrated by 1.8 times by performing a simple distillation operation at 100 ° C. using a 2 L branch flask.
[0038]
The concentration of ammoniacal nitrogen in the obtained condensed water was 3900 mg / L, and the SiO ₂ concentration was 1 mg / L or less. The concentration of ammoniacal nitrogen in the concentrated water was 60 mg / L.
[0039]
【The invention's effect】
As detailed above, according to the method for treating wastewater containing hydrogen peroxide and ammonia of the present invention,
(1) Hydrogen peroxide and ammonia in waste water can be safely and efficiently treated under relatively low temperature and low pressure operating conditions.
(2) Maintenance management is easier than biological treatment, and the installation area of the apparatus can be reduced and sludge is not generated.
(3) Addition of chemicals is unnecessary.
(4) Ammonia can be recovered and used effectively.
Etc. are produced.
[Brief description of the drawings]
FIG. 1 is a system diagram showing an embodiment of a method for treating wastewater containing hydrogen peroxide and ammonia according to the present invention.
[Explanation of symbols]
1 Hydrogen peroxide decomposition equipment 2 Ammonia volatilization tower

Claims (3)

Platinum, palladium, ruthenium, rhodium, indium, iridium as an active catalyst component under the conditions of 20 ° C. to less than 100 ° C. and under normal pressure to a pressure capable of maintaining a liquid phase of waste water containing hydrogen peroxide and ammonia In contact with a catalyst carrying one or more selected from silver, gold, cobalt, copper, nickel and tungsten, and a water-insoluble or poorly water-soluble compound of these metals on a carrier. After decomposing hydrogen and discharging oxygen gas generated by decomposition of hydrogen peroxide to the outside of the system , the ammonia is volatilized and removed under conditions of 20 ° C. or higher and lower than 100 ° C. and normal pressure or lower. To treat wastewater containing hydrogen peroxide and ammonia. Platinum, palladium, ruthenium, rhodium, indium, iridium as an active catalyst component under the conditions of 20 ° C. to less than 100 ° C. and under normal pressure to a pressure capable of maintaining a liquid phase of waste water containing hydrogen peroxide and ammonia In contact with a catalyst carrying one or more selected from silver, gold, cobalt, copper, nickel and tungsten, and a water-insoluble or poorly water-soluble compound of these metals on a carrier. After decomposing hydrogen and discharging oxygen gas generated by the decomposition of hydrogen peroxide to the outside of the system , ammonia is volatilized and condensed under conditions of 20 ° C. to less than 100 ° C. and normal pressure or less. A method for treating wastewater containing hydrogen peroxide and ammonia. Platinum, palladium, ruthenium, rhodium, indium, iridium as an active catalyst component under the conditions of 20 ° C. to less than 100 ° C. and under normal pressure to a pressure capable of maintaining a liquid phase of waste water containing hydrogen peroxide and ammonia In contact with a catalyst carrying one or more selected from silver, gold, cobalt, copper, nickel and tungsten, and a water-insoluble or poorly water-soluble compound of these metals on a carrier. After decomposing hydrogen and discharging oxygen gas generated by decomposition of hydrogen peroxide to the outside of the system , ammonia is volatilized under conditions of 20 ° C. to less than 100 ° C. and below normal pressure, and the ammonia after volatilization is catalyzed. A method for treating wastewater containing hydrogen peroxide and ammonia, which is decomposed by contacting with water.

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