JP3239502B2 - Method for treating water containing volatile organic halogen compounds - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in a method for treating volatile organic halogen compound-containing water. More specifically, the present invention relates to a method for efficiently performing liquid phase reductive decomposition of a volatile organic halogen compound in water to be treated by removing or suppressing the influence of coexisting substances in the volatile organic halogen compound-containing water. is there.

[0002]

2. Description of the Related Art Volatile organic halogen compounds are one of environmental pollutants such as groundwater, soil and air, and it is necessary to remove the compounds. Various methods of treating wastewater, wastewater, groundwater, or soil bleed gas or exhaust gas have been studied.
As this treatment method, for example, (1) volatilization (aeration) treatment, (2) adsorption treatment, (3) oxidative decomposition treatment, (4) biological treatment, and (5) thermal decomposition treatment are known. However, each of these methods has some problems,
It is not always satisfactory. For example, the method (1) simply transfers volatile organic halogen compounds mixed in groundwater or soil to the atmosphere. Also,
The method (2) is a method for adsorbing and recovering a volatile organic halogen compound, and is often used in combination with the method (1). In this case, it is necessary to regenerate the adsorbent. During regeneration, regenerated effluent and exhaust gas containing a high concentration of the compound are discharged. Since these pollutants remain as they are, they cannot be a fundamental solution to environmental problems, and require a decomposition treatment technique capable of rendering the compounds harmless. As a method of decomposing a volatile organic halogen compound, the above-mentioned methods (3) to (5) have been studied. However, the method (3) is a method utilizing ultraviolet rays, ozone, hydrogen peroxide, etc., but requires a large amount of energy for ultraviolet irradiation, generation of ozone, heating, and the like.
It is inevitable that costs will increase. Although the processing methods (4) and (5) have been reported, there are not many examples. As described above, a practical method for efficiently detoxifying volatile organic halogen compounds has not been found yet.

[0003]

SUMMARY OF THE INVENTION Under such circumstances, the present invention can efficiently decompose a compound in water containing a volatile organic halogen compound by decomposing the compound.
It is an object of the present invention to provide a method for treating volatile organic halogen compound-containing water that can perform a stable treatment operation for a long time.

[0004]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies to achieve the above object, and as a result, after removing metal ions in water containing volatile organic halogen compounds in advance, in the presence of a metal catalyst. It has been found that the object can be achieved by bringing the metal ion-removed water into contact with a reducing agent, and the present invention has been completed based on this finding. That is, the present invention is characterized in that after removing metal ions in the volatile organic halogen compound-containing water in advance, the metal ion-removed water and the reducing agent are contacted in the presence of a metal catalyst, A method for treating water is provided.

Hereinafter, the present invention will be described in detail. Examples of the volatile organic halogen compound-containing water to be subjected to the method of the present invention include, for example, volatile organic halogen compound-containing water from various production processes, water and wastewater containing volatile organic halogen compounds, groundwater, and even soil. And those obtained by extracting the volatile organic halogen compound to be obtained with water or the like. In the method of the present invention, the volatile organic halogen compound in the volatile organic halogen compound-containing water is subjected to a liquid phase reductive decomposition treatment. In this case, in order to achieve a stable liquid phase reduction treatment for a long time, It is necessary to remove coexisting substances contained in water and affecting liquid phase treatment performance. As the influence of the coexisting substance on the liquid phase treatment, it is assumed that the coexisting substance is involved in the catalytic reaction itself, a physical influence due to fouling on the catalyst surface, and the like. Examples of such coexisting substances that have an adverse effect on the liquid phase treatment include metal ions such as iron, manganese, and a hardness component. As a method for removing these metal ions, for example, an ion exchange treatment, a chelate exchange treatment, or the like can be used. In addition, when iron and manganese in the water to be treated are removed, an oxidation / coagulation / sedimentation treatment method can be used. In the method of the present invention, after the metal ions in the volatile organic halogen compound-containing water are thus removed in advance, the metal ion-removed water is brought into contact with a reducing agent in the presence of a metal catalyst to form a volatile organic compound. The halogen compound is subjected to a liquid phase reductive decomposition treatment. The metal catalyst is preferably a metal supported on a carrier.Examples of the metal include platinum, palladium, ruthenium, rhodium, iron, copper, iridium and nickel. Among these, palladium and platinum are preferable. , Ruthenium, rhodium, etc. are preferred,
Particularly, palladium and platinum are preferred. These noble metals are used in the form of metals, oxides, hydroxides and the like. Also,
Examples of the carrier include alumina, silica, silica-alumina, titania, activated carbon, zirconia, zeolite, glass, plastic pellets, and ion-exchange resins. Of these, alumina, zirconia and ion-exchange resins are preferred. As the ion exchange resin, a weakly basic anion exchange resin having a styrene-divinylbenzene copolymer as a base is preferable. The supported amount of the metal is
It is usually about 0.1 to 10% by weight based on the carrier.

[0006] The shape of the catalyst is not particularly limited.
Any shape such as a sphere, a pellet, a powder, and a granule can be used, but the sphere, pellet, and a granule may be filled in a column or the like, and the water to be treated may be continuously passed through. Even a powdery material 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, those which generate hydrogen upon contact with the catalyst, such as hydrazine and sodium hydride, and ammonia are used. As a method for treating the volatile organic halogen compound-containing water in the method of the present invention, a metal catalyst is packed in a column, and a treatment solution in which a reducing agent such as hydrogen gas or hydrazine is dissolved is passed through the metal catalyst packed column. Either a continuous system with water or a batch system can be used, but the former continuous system is preferred. In the case of this continuous system, the flow rate of the water to be treated is preferably about 5 to 100 hr ^{-1 in} space velocity. The volatile organic halogen compounds to which the method of the present invention can be applied include those having a boiling point of usually 150 ° C. or lower, preferably 80 ° C. or lower, such as trichloroethylene, tetrachloroethylene, trans-1, 2
-Dichloroethylene, cis-1,2-dichloroethylene, carbon tetrachloride, chloroethane, methylene chloride, chloroform, vinyl chloride, 1,1-dichloroethane, 1,
Examples thereof include 2-dichloroethane, 1,2-dichloropropane, dichlorobromoethylene, 1,1,1-trichloroethane, bromodichloromethane, chlorodibromomethane, bromoform, and various types of freon. Next, an example of a preferred embodiment of the method of the present invention will be described with reference to the accompanying drawings. FIG. 1 is a schematic diagram of an example of an apparatus for carrying out the method of the present invention. Is supplied to the metal ion removal tower 3 via the pump 2. The water to be treated from which the metal ions have been removed is supplied to a reducing agent dissolving tank 4 together with a reducing agent such as hydrogen gas or hydrazine, and then supplied to a metal catalyst packed tower 5, where the volatile organic halogen compound therein is converted to a liquid. Phase reduction decomposition treatment is performed.

[0007]

Next, the present invention will be described in more detail by way of examples, which should not be construed as limiting the present invention. Example 1 Ion-exchange treatment of raw water Synthetic water (raw water) having the water quality shown in Table 1 was mixed with a hydrogen partial pressure of 3 kg /
Dissolve hydrogen in cm ² · G and add 0.5 wt% Pt / γ-Al ₂
A catalyst layer filled with about 250 g of O ₃ (inner diameter 40 mm, height 2
(00 mm) at an SV of 20 hr- ¹ . The processing performance changed with time, and the removal rate was reduced from about 90% in the initial stage to 50 to 60% after the delivery of about 100 BV. This treated water (A)
Table 1 shows the water quality. Next, the raw water was placed in an ion exchange tower (inner diameter 100 mm, height 120 mm) filled with about 1 liter of an Na-type ion exchange resin (PK-228).
The solution was fed at 20 hr ^-1 , and the water (B) having the quality shown in Table 1 was subjected to liquid phase decomposition under the above conditions. Treatment performance is almost constant (about 85%) even after about 100 BV of water to be treated
No change in performance over time as shown above was observed. Table 1 shows the quality of the treated water (C).

[0008]

[Table 1]

Example 2 Chelate exchange treatment of raw water The raw water used in Example 1 was replaced with a chelate resin (PT207).
, And the chelate-exchanged water was subjected to liquid phase reductive decomposition in the same manner as in Example 1. Although there were some variations, the processing performance was almost constant (about 80 to 90%).

[0010]

According to the present invention, the volatile organic halogen compound can be efficiently removed by removing the metal ions in the water containing the volatile organic halogen compound in advance and then contacting it with a reducing agent in the presence of a metal catalyst. It can be rendered harmless by well performing reductive decomposition treatment, and a stable treatment operation can be performed for a long time.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of an example of an apparatus for performing the method of the present invention.

[Explanation of symbols]

 Reference Signs List 1 Raw water storage tank 2 Raw water supply pump 3 Metal ion removal tower 4 Reducing agent dissolution tank 5 Metal catalyst packed tower

────────────────────────────────────────────────── ─── Continuation of front page (56) References JP-A-5-269475 (JP, A) JP-A-1-201002 (JP, A) JP-B-57-20037 (JP, B2) JP-B-56 42567 (JP, B1) US Patent 5,134,424 (US, A) WO 93/13831 (WO, A1) (58) Fields investigated (Int. Cl. ⁷ , DB name) C02F 1/28 C02F 1/42 C02F 1 / 58 C02F 1/62 C02F 1/70

Claims (1)

(57) [Claims] 1. A volatile organic halogen compound-containing water, comprising: removing metal ions in a volatile organic halogen compound-containing water in advance, and then contacting the metal ion-removed water with a reducing agent in the presence of a metal catalyst. Processing method.