JPH05345189A - Method for treating organic halogen compound-containing waste water - Google Patents

Abstract

PURPOSE:To provide a method for treatment wherein a waste water contg. an org. halogen compd. is efficiently decomposed. CONSTITUTION:Fenton's reaction is suppressed and decomposition reaction of an org. halogen compd. is efficiently performed by adding hydrogen peroxide water into an org. halogen compd.-contg. waste water in the presence of a water soluble complex of a transition metal such as iron and manganese. Therefore, as a metal ion in the water soln. is stabilized, it becomes possible to feed stably a metal ion related with Fenton's reaction and in addition, it becomes possible to recycle the valence number of the metal ion and treatment of the org. halogen compd.-contg. waste water can efficiently be performed.

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 containing organic halogen compounds discharged in the dry cleaning, semiconductor, paint, adhesive manufacturing industries and the like.

[0002]

2. Description of the Related Art Organic halogen compounds such as trichloroethylene and tetrachloroethylene are used in large amounts in various industrial fields as detergents, extractants, diluents, reaction solvents and the like.

Wastewater containing organic halogen compounds discharged in these fields is severely regulated from the viewpoint of the effect on the living body or environmental protection.

As a method for treating wastewater containing such an organic halogen compound, for example, there are aeration and aeration method, an adsorption method with activated carbon, a decomposition method with ultraviolet irradiation or ozone, and a method of decomposing treatment with Fenton's reagent. See JP-A-60-261590 and 63-158188.

[0005]

In the conventional physical treatment methods such as aeration method and activated carbon adsorption method, the former is air pollution, and the latter is air pollution due to incineration of activated carbon after treatment or groundwater pollution due to landfill. And the secondary treatment is required.

Further, the decomposition treatment with ultraviolet rays or ozone is
There are problems such as high equipment costs and operating and maintenance costs.

On the other hand, the treatment method using the Fenton's reagent can detoxify the organic halogen compound by oxidative decomposition and reduce the treatment cost, but the treatment efficiency becomes low in the low concentration region of the organic halogen compound, and most of hydrogen peroxide is It is consumed without contributing to the decomposition of the organic halogen compound.

Therefore, in order to reduce the concentration of the organic halogen compound in the waste water to below the regulated value, it is necessary to add a large amount of hydrogen peroxide and a large amount of metal ion necessary for decomposing hydrogen peroxide.

In consideration of the solubility of the metal ion used, the pH needs to be 4 or less.

[0010]

DISCLOSURE OF THE INVENTION The present invention provides a water treatment method for decomposing an organic halogen compound in wastewater with a metal or a metal ion and hydrogen peroxide to stabilize the metal ion by complexing the metal ion. It enables the recycling of metal ions, controls the rate of Fenton reaction in the presence of a small amount of metal complex, and makes the OH radicals and metal ions generated by the reaction act efficiently on the decomposition of organic halogen compounds. It is characterized by

[0011]

In the present invention, a method of decomposing organic salt compounds such as trichloroethylene and tetrachloroethylene with metal ions and hydrogen peroxide is based on an oxidation reaction called Fenton reaction.

In this reaction, Me ²⁺ and hydrogen peroxide generate OH radicals (.OH) as shown in the equation,
The radicals and Me ³⁺ decompose the organochlorine compound (eg, tetrachloroethylene) into carbon dioxide and hydrochloric acid as shown in the formula to render it harmless.

[0013]

^{Embedded image} Me ²⁺ + H ₂ O ₂ → Me ³⁺ + · OH + OH ⁻

[0014]

Embedded image CCl ₂ = CCl ₂ + Me ³⁺ + 2 · OH + 2
_{^{OH - → 2CO 2 + 4HCl +}} Me 2+

In this reaction, it should be noted that the metal ion is involved in the decomposition reaction of the organochlorine compound in the formula.

Generally, the more polyvalent metal ions are, the more dissolved p
H becomes low. Therefore, the Me ³⁺ ion formed by the formula is hardly dissolved under strong acidity and not only precipitates and significantly delays the reaction of the formula, but also the OH radicals generated by the formula are wasted. Become.

This tendency is also that as the concentration of the organochlorine compound decreases, the probability that OH radicals or Me ³⁺ ions will react with the organochlorine compound decreases, and the decomposition rate slows down. It takes a lot of time to reduce the concentration to below the regulation value.

If the concentrations of hydrogen peroxide and metal ions are increased to increase the amount of OH radicals generated and the amount of dissolved metal ions, the decomposition rate of the organochlorine compound is improved, but a large amount of reagent is consumed.

The present inventors have succeeded in increasing the decomposition efficiency of the organohalogen compound without increasing the amount of hydrogen peroxide added, by allowing the metal complex to be present in the waste water to be treated.

As the metal complex, Fe, Mn, Co, N
Metals whose transition valences of transition metals such as i and Ti or metal ions such as Cu and citric acid, tartaric acid, malic acid,
It is a reaction product of an organic compound that easily forms a complex with a metal such as a monobasic acid, a polybasic acid, an oxycarboxylic acid or an amino acid, such as ascorbic acid, maleic acid, mucus acid or EDTA.

The metal complex may be formed by dissolving or eluting metal ions in the treated wastewater and adding these organic compounds.

In these complexes, hydrogen peroxide decomposes to form O.
O generated by affecting the reaction that generates H radicals
The H radical efficiently acts on the decomposition of the organic halogen compound.

Therefore, it is presumed that the effect of these metal complexes forms a field in which the generated OH radical and the organic halogen compound react efficiently.

The amount of addition varies depending on the concentration of the organic chlorine compound in the waste water and the concentration of hydrogen peroxide,
It suffices if it is present at about 10%.

If it is less than 0.01%, it has almost no effect, and if it is added more than 10%, it causes a problem in water quality standard and is not preferable.

Further, even if an inorganic acid such as hydrochloric acid, sulfuric acid or nitric acid is added in the presence of a metal or a metal oxide without forming a complex, the decomposition efficiency of the organic halogen compound is improved.

It is considered that this is because the acid promotes the dissolution of the metal or the metal oxide and, as a result, the reaction.

These complexes are effective even if one kind is used, but the effect is not changed even when a combination of several kinds is used.

The metals used are Fe, Mn, Co and N.
The Fenton reaction occurs if the composition is one or more of transition metals such as i and Ti or metals whose valence of a metal ion such as Cu can be changed, but Fe-based compositions are preferable. good.

As the metal complex, iron (II) citrate,
Examples of the metal compound such as (III), EDTA (II), and (III) include metal salts such as iron (II) sulfate, (III), iron (II) chloride, (III), and copper (II) sulfate.
Iron (II) oxide, (III), manganese (II) oxide,
Examples thereof include oxides such as (III).

In the case of a metal or an oxide, it is considered that the surface of the metal or oxide is dissolved in the waste water and ionized to have the same action as the metal compound.

The metal or metal compound may be in any shape such as powder, plate, lump, or porous body, but it is preferable that the contact surface is large like a porous filter (Japanese Patent Laid-Open No. 3-114589).

The amount of hydrogen peroxide and the metal complex used may be appropriately determined according to the kind and amount of the organic halogen compound in the waste water and the amount of other organic substances coexisting in the waste water. In wastewater containing an organic chlorine compound, hydrogen peroxide 0.05 to 2%, metal complex 0.1 to 2
Use%.

In the case of a metal or a metal compound, the amount of the metal ion concentration when the metal is dissolved is 0.1 to 3%, and the amount of the organic compound added for complex formation is also in accordance with this.

The treatment temperature is usually room temperature in order to suppress vaporization of the organic chlorine compound, but when the vaporized gas is returned to the treated water, the treatment temperature is not limited, but considering the solubility of the gas, a high temperature is not preferable. it is conceivable that.

In the treatment operation, the treatment efficiency is improved by circulating and agitating the wastewater. The waste water after treatment becomes acidic, so it is neutralized with an alkali, and if necessary, filtered to waste water.

When the concentration of metal ions in the waste water after the treatment becomes too high, the metal ions are removed by a metal coagulant or the like before draining.

[0038]

EXAMPLES The present invention will be described below with reference to examples.

[0039]

Example 1 A container containing 87 ml of tetrachloroethylene 150 ppm solution, 3 ml of 3% hydrogen peroxide, 10 ml of distilled water and 0.1 g of iron (II) citrate was sealed,
When the change over time in the amount of decomposition was measured with an organic chlorine compound detector, a remarkable effect was found as shown in FIG.

[0040]

[Example 2] 3 ml of 3% hydrogen peroxide and 10 ml of a 0.1 mass% organic compound solution as an additive were added to 87 ml of a solution containing 150 ppm of tetrachloroethylene, placed in a container containing 1 g of porous iron, sealed, and allowed to stand for 24 hours. After that, when the amount was measured with an organic chlorine compound detector, as shown in Table 1, a remarkable effect was found when the organic compound was added.

[0041]

[Comparative Example 1] 3 ml of 3% hydrogen peroxide and 10 ml of distilled water in 87 ml of a solution containing 150 ppm of tetrachloroethylene.
Was placed in a container containing 1 g of porous iron and sealed, and after standing for 24 hours, the amount of undecomposed tetrachloroethylene was measured by the same method as in Example 1, and as shown in FIG. 1 and Table 1. Good results were obtained. Table 1 shows the additive effect in the organohalogen compound by the Fenton reaction.

[0042]

[Table 1]

[0043]

EFFECTS OF THE INVENTION According to the present invention, in the treatment of wastewater containing an organohalogen compound using the Fenton reaction, the consumption amount is reduced by improving the utilization efficiency of hydrogen peroxide and metal ions. It becomes possible to easily detoxify the compound.

[Brief description of drawings]

FIG. 1 is a diagram showing a change with time in decomposition of an organic halogen compound by a Fenton reaction.

Front page continuation (72) Inventor Toshio Koike 1618 Ida, Nakahara-ku, Kawasaki City, Nippon Steel Corporation Advanced Technology Research Laboratories (72) Inventor Kengo Senoo 5-3 Tokai-cho, Tokai-shi Nippon Steel Corporation Nagoya (72) Inventor Tatsuo Mukai 2-6-3 Otemachi, Chiyoda-ku, Tokyo Shin Nippon Steel Co., Ltd.

Claims (5)

[Claims] 1. A method for treating wastewater containing an organic halogen compound, which comprises decomposing an organic halogen compound in the wastewater with a metal complex and hydrogen peroxide. 2. The treatment method according to claim 1, wherein an organic compound is added in the presence of a metal or a metal compound, and the eluted or dissolved metal ions are complexed to obtain a metal complex. 3. The treatment method according to claim 2, wherein the organic compound is an organic compound which easily forms a complex with a metal such as a water-soluble monobasic acid, polybasic acid, oxycarboxylic acid or EDTA. 4. The metal or metal compound is Fe, Mn, C.
The treatment method according to claim 2, wherein the metal is a transition metal such as o, Ni, or Ti, or a metal such as Cu whose valence of a metal ion can be changed. 5. The processing method according to claim 2, wherein the shape of the metal or metal compound is a porous body, a powder, a plate, or a lump.