JPH05269476A - Treatment of water containing volatile organohalogen compound - Google Patents

Abstract

PURPOSE:To prevent a volatile organohalogen compd. from becoming a re- pollution source by bringing water containing the volatile organohalogen compd. into contact with a reducing agent in the presence of a metal supported catalyst to efficiently decompose the volatile organohalogen compd. into harmless hydrocarbon and a halogen ion. CONSTITUTION:Water containing a volatile organohalogen compd. is brought into contact with a reducing agent in the presence of a metal supported catalyst to be treated. The catalyst used herein is obtained by supporting a metal on a carrier and, as the metal, a noble metal, for example, palladium, platinum or ruthenium is pref. As the carrier, for example, alumina, titania, activated carbon, an ion exchange resin and the like are designated and, as the ion exchange resin, a weakly basic anion exchange resin based on a styrene/ divinylbenzene copolymer is preferable.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improved method for treating water containing volatile organic halogen compounds. More specifically, the present invention relates to a method for efficiently reducing and decomposing a volatile organic halogen compound contained in water or waste water by using a reducing agent and a catalyst.

[0002]

2. Description of the Related Art Since volatile organic halogen compounds cause environmental pollution, it is necessary to remove the compounds contained in wastewater, etc., and until now, it has been necessary to treat water and wastewater containing volatile organic halogen compounds. Various methods have been studied. Examples of treatment methods for water and wastewater containing this volatile organic halogen compound include (1) aeration treatment, (2) adsorption treatment, (3) oxidative decomposition treatment, (4) biological treatment, and (5)
Pyrolysis treatment and the like are known. However, all of these methods have some problems and are not always satisfactory. For example, the method (1) merely transfers organic halogen compounds mixed in groundwater or soil to the atmosphere, and does not become a drastic solution to environmental problems. The method (2) is a method capable of trapping and recovering an organohalogen compound, and is often used in combination with the method (1), but in this case, the adsorption capacity of the adsorbent (activated carbon etc.) It is inevitable that it will be greatly affected by the impact. In addition, the adsorption treatment method requires regeneration of the adsorbent, and in the case of performing steam regeneration or the like, regeneration waste liquid containing a high-concentration organic halogen compound is discharged. For the purpose of radically solving environmental pollution, the decomposition treatments (3) to (5) described above are required. Among them, the oxidative decomposition method (3) has been extensively studied as a decomposition treatment method for organic halogen compounds, and many methods utilizing ultraviolet rays, ozone, hydrogen peroxide and the like have been reported.
In addition, the decomposition treatment methods (4) and (5) have been reported, but not many. In the oxidative decomposition method or the thermal decomposition method, the amount of energy required for the generation of ultraviolet rays or ozone, or the heating is large, and inevitably the cost is high. It has a problem that it easily re-reacts, and a new organic halogen compound may be generated. Also,
Although the biological treatment method of (4) requires a small amount of input energy, a microorganism that decomposes efficiently has not been found yet.
Not a practical method. On the other hand, a method using iron powder as a reductive decomposition method has been reported, but it is not completely satisfactory.

[0003]

DISCLOSURE OF THE INVENTION The present invention overcomes the drawbacks of the conventional treatment method for water containing a volatile organic halogen compound, and reduces the amount of volatile organic halogen compound in water or wastewater with a small amount of energy administration. Efficiently decomposes and removes
In addition, the object of the present invention is to provide a method for treating water containing a volatile organic halogen compound that does not regenerate a new organic halogen compound.

[0004]

Means for Solving the Problems As a result of intensive studies to achieve the above-mentioned object, the present inventors have found that water containing a volatile organic halogen compound is brought into contact with a reducing agent in the presence of a metal-supported catalyst. The volatile organic halogen compound is efficiently decomposed into harmless hydrocarbons and halogen ions,
Moreover, it was found that the generated halogen ions are difficult to re-react with coexisting organic substances, and the present invention has been completed based on this finding. That is, the present invention provides a method for treating volatile organic halogen compound-containing water, which comprises contacting volatile organic halogen compound-containing water with a reducing agent in the presence of a metal-supported catalyst.

The present invention will be described in detail below. The catalyst used in the method of the present invention is one in which a metal is supported on a carrier, and examples of the metal include palladium, platinum, ruthenium, rhodium, copper, iron and the like. Among these, palladium and platinum , Noble metals such as ruthenium and rhodium are preferable, and palladium is particularly preferable. As the palladium, metallic palladium, palladium oxide, palladium hydroxide or the like is used. Also,
Examples of the carrier include alumina, titania, activated carbon, zirconia, zeolite, glass, silica, ion exchange resins, plastic pellets and the like, among which alumina, zirconia and ion exchange resins are preferable. As the ion exchange resin, a weakly basic anion exchange resin having a styrene-divinylbenzene copolymer as a matrix is preferable. The amount of the metal supported is usually 0.
It is about 1 to 10% by weight.

The shape of the metal-supported catalyst is not particularly limited, and any shape such as powder, granules and pellets can be used. Granules or pellets are packed in a column or the like and continuously packed. It is advisable to pass the liquid to be treated. Even the powder form can be packed in a column and operated in a fluidized bed state. As the reducing agent used in the method of the present invention, in addition to hydrogen gas, for example, hydrazine, sodium hydride or the like that generates hydrogen by contacting with the catalyst is used.

Further, the volatile organic halogen compound to which the method of the present invention can be applied is usually a volatile compound having a boiling point of 150 ° C. or lower, preferably 80 ° C. or lower. Trans-1,2-dichloroethylene, cis-1,2
-Dichloroethylene, carbon tetrachloride, chloroethane, methylene chloride, chloroform, vinyl chloride, 1,1,1-
Trichloroethylene, 1,1-dichloroethane, 1,2-
Dichloroethane, 1,2-dichloropropane, dichlorobromoethylene, 1,1,1-trichloroethane, bromodichloromethane, chlorodibromomethane, bromoform and the like can be mentioned. In the method of the present invention, a volatile organic halogen compound is reductively decomposed using a metal-supported catalyst and a reducing agent. As an example, when the volatile organic halogen compound is trichlorethylene, decomposition is carried out according to the following reaction formula. It is supposed to happen.

2CHCl = CCl ₂ + 3H ₂ → 2CH ₂ =
CH ₂ + 6Cl ^−, that is, trichlorethylene is dechlorinated to produce ethylene and chloride ions. This chlorine ion is HCl
It is stable and does not become a source of recontamination. In addition to ethylene, the production of methane and ethane is also recognized. In the method of the present invention, the addition amount of the reducing agent is usually selected in the range of 10 to 1,000 mg / liter. As the method for treating the volatile organic halogen compound-containing water in the method of the present invention, either a continuous method in which a metal-supported catalyst is packed in a column, and water to be treated and a reducing agent are passed through, or a batch method is used. However, the former continuous method is preferable. In the case of this continuous system, the flow velocity of the water to be treated is preferably about ¹ to 100 hr ^{−1 in} SV.

[0009]

The present invention will be described in more detail by way of examples, which should not be construed as limiting the invention thereto.

Example 1 Approximately 300 ppb in a vial bottle having an internal volume of 22 ml
10 ml of trichlorethylene solution of
To this was added 0.5 g of a catalyst carrying 0.5% by weight of various metals (support is alumina) and 3.2 mg of hydrazine, and the mixture was added at 25 ° C.
Well stirred. A part of the upper headspace was sampled at regular intervals and analyzed by gas chromatography. For comparison, data without addition of hydrazine were also obtained. The results are shown in Table 1.

[0011]

[Table 1]

Example 2 In the same manner as in Example 1, except that an aqueous solution of about 200 ppb trichloroethylene was used, palladium was used as a metal, and various carriers were used. An attempt was made to decompose trichlorethylene. The results are shown in Table 2.

[0013]

[Table 2]

Example 3 A water flow experiment was conducted using the apparatus shown in FIG. Inner diameter 15mm
The column 1 was packed with 16.2 g of a catalyst supporting 0.5% by weight of palladium on alumina so that the length of the catalyst layer 2 would be 100 mm, and then the raw water storage tank 3 and the pump 4
The trichloroethylene solution of about 300 ppb was passed by the SV at about 10 hr ⁻¹ . On the other hand, hydrazine aqueous solution storage tank 5
A pump 6 was used to introduce an aqueous hydrazine solution so that the concentration in the water to be treated was 250 ppm. The treated water was collected and the head space was analyzed by gas chromatography. The processing temperature is 25 ° C. The results are shown in Table 3.

[0015]

[Table 3]

Example 4 The same procedure as in Example 3 was carried out except that various volatile organic halides were used instead of trichlorethylene and the addition amount was changed. The results are shown in Table 4.

[0017]

[Table 4]

[0018]

According to the present invention, water containing a volatile organic halogen compound is brought into contact with a reducing agent in the presence of a metal-supported catalyst to convert the volatile organic halogen compound into harmless hydrocarbons and halogen ions. It can be decomposed efficiently, and the generated halogen ions do not easily react with the coexisting organic matter, so that it does not become a recontamination source.

[Brief description of drawings]

FIG. 1 is a schematic diagram of an apparatus used in Example 3.

[Explanation of symbols]

 1 column 2 catalyst layer 3 raw water storage tank 4 pump 5 hydrazine aqueous solution storage tank 6 pump

Claims (1)

[Claims] 1. A method for treating volatile organic halogen compound-containing water, which comprises contacting volatile organic halogen compound-containing water with a reducing agent in the presence of a metal-supported catalyst.