First, chlorination
Chlorine is a very effective oxidant for cyanide. Commonly used chlorine reagents are chlorine gas, sodium hypochlorite and calcium hypochlorite. Alkaline liquid chlorination is the most common method of destroying cyanide in solution. The liquid discharged from the heap can be chlorinated and returned to the heap for residual cyanide in the destructive loop. Other leachates can be treated similarly. The reaction of free cyanide and chlorine is fast and efficient. Only iron complexed cyanide is resistant to chlorination.
At the end of the leaching, the leaching residue is treated with a 0.5 g/L industrial grade calcium hypochlorite solution, which consumes 272.4 g of calcium hypochlorite per t residue. This method is fast and effective.
Second, air - sulfur dioxide
Recently, INCO used air-S0 2 or air-sulfite to destroy cyanide to a relatively low level. Under the condition of pH control and a small amount of copper as a catalyst, the cyanide can be rapidly decomposed by mixing with wastewater and SO 2 air. Selectively oxidizing the cyanide and cyanide complexes of metals, but also to remove iron cyanide complexes by alkaline chlorination can not be removed. This treatment can be carried out at room temperature using only lime water, SO 2 and air, and the residual total cyanide content is between 0.05 and 1 mg/L (between pH 9 and 10). It is currently considered to be the most economical and effective method.
Third, hydrogen peroxide
Cyanide can also be destroyed by H 2 O 2 , but the cost is too high.
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