Cyanide-containing waste

Thiocyanate is a monovalent polyanion that has the formula SCN-. This anion is rarely found in wastewaters. However, cyanide-containing wastes or waters on contact with sulfides can form thiocyanates. On chlorination, thiocyanate could react with chlorine to form highly toxic cyanogen chloride, CNC1. Thiocyanate in water may be analyzed using 1. colorimetric method and 2. spot test. The latter method is a rapid spot test that can give semiquantitative results. Preserve samples at pH below 2 and refrigerate. 

Treatment of Cyanide-Containing Waste Water from Gold Mine Operation by Liquid Membrane Technology. News release in Kexue Bao (Newspaper of Science), China, October 16, 1987. 

Commercially, CICN has been produced, in the main, by the chlorination of aqueous HCN. An unintended synthesis of CICN may occur during the treatment of cyanide-containing waste water with chlorine or hypochlorite. Aspects of this issue have been considered by Bailey and Bishop (1973a). 

Metal/Cyanide-Containing Wastes Treatment Technologies... 

Blast furnace sludge resulting from production of pig iron. In this process, sodium and potassium cyanides are generated in the blast furnace and leave as dust in the top gas. This top gas is subjected to wet scrubbing, which results in a muddy cyanide containing waste (Mansfeldt Biemath 2001). 

The high toxicity of [CN] makes it essential for cyanide-containing waste produced by industry to be treated. Several methods are used. For dilute solutions of cyanide, destruction using hypochlorite solution is common ... 

Example 4.2-1 Cyanide dispersion A metal stamping company has inadvertently spilled cyanide-containing waste into a small creek. Behaving responsibly, they notified the local environmental authorities who arrived promptly to analyze the creek water. These authorities find that the concentration 2 km downstream has a maximum of 860 ppm and a concentration 50 m from the maximum of 410 ppm. The stream is flowing at 0.6 km/hr. (a) What dispersion coefficient is implied by these results How does it compare with the diffusion coefficient (b) What will the maximum concentration be 15 km downstream ... 

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