JPS587357B2 - cyanobunkaihouhou - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a significantly improved method for decomposing cyanide or cyanide coexisting with metals.

Specifically, cyanide or cyanide solutions coexisting with metals, which are being discharged from chemical product or intermediate manufacturing plants, metal surface treatment plants, city gas production plants, ammonia synthesis plants, etc., or silver halide photographic materials; Hypochlorites such as sodium hypochlorite, potassium hypochlorite, calcium hypochlorite, etc. are added to cyanide or cyanide solutions that coexist with metals, such as processing solutions for blueprints, analytical reagent solutions, etc., and water. It is characterized by adding an alkali such as sodium oxide, potassium hydroxide, and soda carbonate, and a compound that provides bromide ions in the reaction system of the present invention, such as bromine, sodium bromide, potassium bromide, and calcium bromide. This invention relates to a method for decomposing cyanide or cyanide coexisting with metal, which is carried out by heating if necessary.

Conventionally, in order to decompose these cyanides or cyanide that coexists with metals, for example, "Pollution Prevention Technology, Laws and Water Quality Edition" (February 24, 1970, 1st edition, published, supervised by Pollution Safety Bureau, Ministry of International Trade and Industry) , published by Industrial Pollution Control Association) 191
[Although the alkali chlorine method is generally practiced as seen in JP-A No. 48-168941, etc., the conventional method involves decomposing cyanide in the solution using hypochlorite and an alkali to detoxify it. requires a large amount of hypochlorite, and cyanide, especially when it coexists with metals, often exists in the form of difficult-to-decompose cyano complex salts. This method has drawbacks such as the need to use an extremely large amount of hypochlorite and to process under extremely harsh conditions, making it a very disadvantageous method on an industrial scale.

The present inventors have made extensive studies, and when cyanide or cyanide that coexists with metals is decomposed by adding hypochlorite and alkali, bromine or a compound that provides bromine ions in the reaction system of the present invention is added, and a small amount of cyanide is added. The present invention has been completed, which is industrially useful and effectively decomposes cyanide with a high decomposition rate under mild conditions using hypochlorite.

In particular, when cyanide forms a complex due to its coexistence with a metal, it is extremely difficult to decompose and detoxify it, but it is quite surprising that this can be accomplished extremely easily by adding a small amount of bromide ion. It is the right thing to do.

Examples of the hypochlorite used in the present invention include sodium hypochlorite, potassium hypochlorite, calcium hypochlorite, and the like. Although it depends on various conditions such as whether cyanide coexists with the metal, decomposition temperature, decomposition time, etc., it is usually sufficient to use less than three times the theoretical amount of cyanide.

The alkali used in the present invention includes sodium hydroxide, potassium hydroxide, soda carbonate, calcium hydroxide, barium hydroxide, etc., and the amount of the alkali is such that the reaction in the method of the present invention can always be carried out in an alkaline state. It is enough if there is.

The bromide ions used in the present invention are compounds that provide bromide ions in the reaction system of the present invention, and include bromine, sodium bromide, potassium bromide, calcium bromide, barium bromide, aluminum bromide, etc. Can be mentioned.

The amount of the compound that provides these bromine ions used is usually 5% or less based on the total amount of the solution.

Cyanide that can be decomposed includes cyanide when no metal coexists, and cyanide when metals such as iron, nickel, copper, zinc, silver, and cadmium coexist.
The decomposition reaction proceeds satisfactorily even at room temperature, but if rapid treatment is desired, it is preferably carried out at 50°C to 80°C.

The advantages of the present invention include that cyanide can be decomposed under mild conditions, and that cyanide that coexists with metals that are normally extremely difficult to decompose can be easily decomposed.
Furthermore, since only a small amount of hypochlorite is required for industrial use, the processing efficiency is good and raw material costs are low, making industrial implementation very effective and efficient. It is in.

Examples are given below to further explain the present invention.

In the examples, parts expressing quantities are parts by weight.

Example 1 To 1000 parts of an aqueous solution containing 1000 ppm of cyanide as a cyanide root (CN-), 82 parts of a 13% sodium subzinc chlorate aqueous solution (theoretical amount x 1.5), 10 parts of a 50% sodium hydroxide aqueous solution, and bromide were added. Add 2.5 parts of sodium,
Incubate at 5°C for 30 minutes.

Nitrogen gas, carbon dioxide gas, hydrochloric acid gas generated during the decomposition process,
Gases such as hydrogen bromide gas are recovered or treated by known methods.

The solution after the completion of the decomposition reaction was clear and colorless, and the amount of cyanide contained was 0.1 ppm (decomposition rate was considered to be 100%).

Example 2 13% sodium hypochlorite aqueous solution, 50% sodium hydroxide aqueous solution and sodium bromide were added as shown in the table below to 1000 parts of waste liquid containing 1000 ppm of red blood salt as cyanide (CN-) and reacted. let

After the completion of the decomposition reaction, the precipitate is separated and recovered from the waste liquid, and the supernatant water is discharged as waste water.

This supernatant water is clear and colorless, and contains 0.1 cyanide.
ppm or less (decomposition rate 100%).

Example 3 165 parts of 13% NaClO (Th
x3) Add 20 parts of 50% sodium hydroxide and 2.5 parts of potassium bromide, and then heat at 50°C for 30 minutes.

Thereafter, the same treatment as in Example 1 was carried out, and the decomposition rate was 100%.

Example 4 110 parts of 13% NaClO (T
h×2), 20 parts of 50% potassium hydroxide, and 2.0 parts of bromine.
Add 5 parts and then warm at 25° C. for 2 hours.

Thereafter, the same treatment as in Example 1 was carried out, and the decomposition rate was 100%.

Example 5 Zn. (C.N) 1000p with 42-F as cyan root
Add 13 parts of calcium hypochlorite to 1000 parts of waste liquid containing PM.
．． 8 parts (Th×2), 20 parts of calcium hydroxide, and 2.5 parts of sodium bromide are added, and then heated at 50° C. for 30 minutes.

Thereafter, the same treatment as in Example 1 was carried out, and the decomposition rate was 100%.

Claims (1)

[Claims] 1. A system containing cyanide, a hypochlorite, an alkali,
A cyanide decomposition method characterized by the addition of bromine ions. 2. A cyanide decomposition method characterized by adding hypochlorite, an alkali, and bromide ions to a system containing cyanide and metal.