JP2003062556A - Method for removing arsenic compound in soil and removing chemical of the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for decomposing and removing an indecomposasble arsenic compound from soil and a removing chemical of the same. SOLUTION: Soil contaminated with arsenic is heated after adding a reducing agent thereto. It is preferred that the soil is heated under a low-oxygen concentration condition. A nitrogen atmosphere is preferred as the low-oxygen concentration condition. The reducing agent used is selected from the group consisting of heavy oil, coal, coke, salts of low oxyacids (NaH2 PO2 , Na2 S2 O3 and the like), hydrides (LiAlH4 and the like), hydrazines, diimides, aldehydes and saccharaides. It is preferred that, as the reducing agent, saccharaides such as starch are easily available at cheap prices.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method and agent for removing arsenic compounds in arsenic-contaminated soil.

[0002]

2. Description of the Related Art Most of the heavy metals are removed from the soil by heating, washing or the like in the case of purifying heavy metal contaminated soil, but advanced removal methods have not been established for arsenic.

[0003]

The arsenic-contaminated soil may contain decomposable arsenic compounds such as iron salts and silicates, and even if these are subjected to heat treatment or acid / alkali cleaning, It remains in the soil without decomposition.

An object of the present invention is to provide a method and a drug for decomposing and removing the above-mentioned hardly decomposable arsenic compound from soil.

[0005]

The method for removing arsenic compounds contained in soil according to the present invention is a method characterized by adding a reducing agent to arsenic-contaminated soil and then heating the same.

In the above method, it is preferable to heat the soil under low oxygen conditions. A nitrogen atmosphere is preferable as the low oxygen condition.

The reducing agent used in the method of the present invention includes heavy oil, coal, coke, and lower oxyacid salts (NaH ₂ PO ₂ , N ₂₎ .
a ₂ S ₂ O _3, etc.), hydride (LiAlH ₄
Etc.), hydrazine, diimides, aldehydes and sugars. As the reducing agent, sugars such as starch are preferable because they are easily available and inexpensive.

The present invention provides an agent for removing arsenic compounds in soil, which contains a reducing agent. The reducing agent is usually used after being dissolved or suspended in water.

In a preferred embodiment, the treated soil is sent to a stirrer, to which the arsenic compound-removing agent according to the present invention is added in an amount of 1 to 100% by weight with respect to the soil to uniformly mix the whole.
Heat treatment is performed under low oxygen conditions.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION Next, the present invention will be specifically described based on Examples.

Comparative Example 1 1) Soil having an arsenic content of 10% by weight (as As) was used in the air or in a nitrogen atmosphere in an amount of 600 to 600% without adding a chemical agent.
Heat treatment was performed in the temperature range of 1000 ° C. for 1 hour, and arsenic in soil before and after the treatment was quantified by fluorescent X-ray analysis. The results are shown in Table 1.

[0012]

[Table 1]

As can be seen from Table 1, arsenic volatilization from this soil was hardly seen.

Example 1 To a soil having an arsenic content of 10% by weight (as As), 5% by weight of starch was added to the soil, and after stirring and mixing, the temperature range was 600 to 1000 ° C. in air and nitrogen atmosphere. In 1
After heat treatment for a period of time, arsenic in soil before and after the treatment was quantified by fluorescent X-ray analysis. The results are shown in Table 2.

[0015]

[Table 2]

As can be seen from Table 2, the removal rate of arsenic in soil was 5 to 7% in the air atmosphere treatment, but the removal rate was increased in the nitrogen atmosphere treatment, and the arsenic removal rate was 59% in the treatment at 1000 ° C. was.

Example 2 Except that the amount of starch added was changed to 20% by weight with respect to the soil,
The same operation as in Example 1 was performed to quantify the arsenic in the soil before and after the treatment by fluorescent X-ray analysis. The results are shown in Table 3.

[0018]

[Table 3]

As can be seen from Table 3, the removal rate of arsenic in soil by the treatment in air was 15 to 23%, but the removal rate increased in the treatment in the nitrogen atmosphere, and the arsenic treatment in the treatment at 1000 ° C increased. The removal rate reached 99%.

[0020]

In the method of the present invention, since the reducing agent is added to the arsenic-contaminated soil and then the same is heated, the removal rate of arsenic in the soil is remarkably improved as compared with the case where the reducing agent is not added.
Further, when the heat treatment is performed under a low oxygen condition, the removal efficiency of arsenic in soil is improved as compared with the heat treatment in air.

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Rei Fukatsu             1-89 Minami Kohoku 1-89, Suminoe-ku, Osaka             Standing Shipbuilding Co., Ltd. F-term (reference) 4D004 AA41 AB03 CA22 CA34 CA37                       CC11 CC15 CC16 DA02 DA06                       DA10

Claims (5)

[Claims] 1. A method for removing an arsenic compound in soil, comprising adding a reducing agent to the arsenic-contaminated soil and then heating the soil. 2. The method for removing an arsenic compound in soil according to claim 1, wherein the soil is heated under a low oxygen condition. 3. The method for removing an arsenic compound in soil according to claim 1, wherein the reducing agent is selected from the group consisting of heavy oil, coal, coke, lower oxyacid salt, hydride, hydrazine, diimide, aldehyde and saccharide. . 4. The method for removing an arsenic compound in soil according to claim 3, wherein the saccharide is starch. 5. An agent for removing an arsenic compound in soil, which comprises a reducing agent.