JPS6043192B2 - Method for preventing arsenic leaching in arsenic-containing waste - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a treatment method for preventing arsenic from being leached from solid, semi-liquid or liquid waste containing arsenic (hereinafter simply referred to as arsenic-containing waste). .

Industrial waste is usually disposed of by land-filling or ocean dumping, but attention has been drawn to the fact that arsenic is leached from these disposed industrial wastes and pollutes the environment. In order to prevent this, an arsenic elution test was required by Official Gazette Extra No. 13 dated February 17, 1939, and if the arsenic elution was less than the standard value, the above-mentioned punishment would be carried out. It turned out that it wasn't going to happen. Therefore, as an industry that discharges sludge or waste liquid containing arsenic,
There is an urgent need to establish a processing method that can comply with such regulations.

So far, arsenic has reached the standard value in elution tests.
．． For the treatment of sludge and liquid waste that elute in excess of 5m9ll (ppm), a method of covering and solidifying these wastes with concrete is widely adopted.

However, this solidification method simply covers the arsenic-containing waste with concrete and solidifies the outer periphery to prevent the arsenic-containing waste from leaking out, and does not require the use of solidification equipment or cement. In addition to the economic problems associated with this, there are also concerns about arsenic leaking due to concrete damage.

The present invention aims to provide a processing method that can solve these problems.

According to the present invention, by directly adding any one of salts such as ferrous salts or ferric salts, and waste acids containing ferrous ions or ferric ions to arsenic-containing waste, Elution of arsenic from the arsenic-containing waste can be prevented. Examples of arsenic-containing waste to which the present invention is directed include waste acid sludge discharged from special glass factories, ceramic factories, agricultural chemical manufacturing factories, and the like.

To treat arsenic-containing waste, use ferrous or ferric salts such as ferrous sulfate, ferric sulfate, ferrous chloride, ferric chloride, and ferrous ions or ferric ions. One type from the group consisting of waste acids is used alone.

These iron salts, or waste liquids containing ferrous or ferric ions can be obtained free of charge or at very low cost, and in some cases may be obtained with a waste disposal fee paid. .

These processing agents are mixed with the arsenic-containing waste to be treated (if they are in the same shape, they are dissolved in water, or if they are in liquid form, they are left as is). In the treatment method of the present invention, by adding salts of ferrous salt ions or ferric salts or waste liquid containing ferrous ions or ferric ions as a treatment agent, the amount of arsenic eluted is determined by an elution test. It is thought that the following mechanism is responsible for the decrease or undetectability.

When an elution test is performed on waste containing ferrous ions or ferric ions by adding the treatment agent, if the pH value after elution is adjusted to weak acidity or alkalinity, Iron ions form ferrous hydroxide, and ferric ions form ferric hydroxide, which precipitate as flocs.

At this time, arsenic in liquid or solid waste co-precipitates with iron hydroxide flocs to form a stable iron hydroxide-arsenic complex and is removed from the liquid, so that arsenic is not detected in the eluate. This is considered to be the case. As shown in the examples below, the amount of iron salt added is sufficient to be 2-1@ of the amount of arsenic contained.
Adding a slight excess ensures that the purpose of arsenic removal is achieved. The present invention will be explained below with reference to Examples. Example 1 As a laboratory method, arsenic acid (HAsO2) was dissolved in water, and sulfuric acid,
Two test solutions were prepared with the amount of iron added at 20 ppm and 50 ppm.

After adjusting the pH value of this test solution to 8.0, it was shaken for 6 minutes, and then tested using No. 1 paper. At 5? The amount of arsenic in the liquid was measured according to the factory wastewater test method JISKOIO2, 48-2.

It was found that the elution of arsenic could be prevented by adding 20 ppm of ferric sulfate, which is twice as much.

Example 2 An amount of sludge containing 10 ppm of arsenic was prepared, and the amount of sulfuric acid waste solution containing 8.4% of ferric ions added to the sludge was tested in five stages as shown below.

The above results show that the use of waste liquid containing ferric ions prevents the elution of arsenic from arsenic-containing sludge.

The amount of waste acid containing ferric ions added is 100 pp.
It was recognized that the arsenic content should be 10f8 or more. Example 3 A test was conducted for the purpose of examining the influence of the pH value upon pH adjustment on arsenic removal in a solution prepared by adding a processing agent to arsenic-containing waste.

Ferric chloride 5 was added to the sludge containing the equivalent of 10 ppm arsenic.
0 ppm was added, the pH value was adjusted as shown below, and an elution test was conducted in accordance with Environment Agency Notification No. 13.
It was measured by From this result, it can be seen that the higher the pH value of the eluate, that is, the stronger the alkalinity, the greater the effect of preventing arsenic elution.

Example 5 A waste solution containing 10 ppm of arsenic was adjusted by adding water so that the solid content was 3%, and a waste acid containing ferric sulfate (Fe
(8.4%) was added in the following three types.

The pH value of this mixture was adjusted to 8.0, and the amount of arsenic in the p liquid was measured in the same manner as in the above example.

From the above results, the elution of arsenic can also be prevented by adding a ferric salt.

Claims (1)

[Claims] 1 For solid, semi-liquid or fluid waste containing arsenic,
A salt or waste acid mainly composed of one selected from the group consisting of a ferrous salt or a ferric salt and a waste acid containing more than 50% of ferrous ions at a pH of 5 to 12. Adjust the amount of arsenic within the range and use it as a treatment agent, and add an amount that exceeds the preset amount depending on the amount of arsenic in the waste and the type of treatment agent, thereby reducing the amount of arsenic eluted below the regulatory value. A method for preventing elution of arsenic in arsenic-containing waste, characterized by reducing the elution of arsenic in arsenic-containing waste.