Handling and Discarding Cyanide

Given to its high toxicity, the cyanide demands a cerful handling every time that the personnel of the plant is exposed to its contact, both in the solutions as with the powder that is let out during the preparation of the same, a third form of exposition through the formation of prusic acid (HCN) gasseous is minimized mantaining a pH of protection between 10 and 11 in the sollutions; in the cyanidation in heap leaching, because we are talking about an operation conducted in open precincts with ventilation, this exposition is practically incapable of happening. The industrial experience has shown that, with instruction and plans of training, the cyanide can be handled routinely with little risk for the operator.

On the other hand, the protection of the environment also requires of means to avoid the contamination of superficial or underground currents in local areas. Consequently all the system of channelling of the solutions (floor, wells, reservoirs, channels, tubing, etc.) must be projected attending this aspect in a special form, including, considering the additional capacity of the storing in the case of rain. The losses by evaporation generally allow the recycling of the sollutions in total, but facing an exceptional situation of discarding, these have to be previously treated with a strong oxydant to decompose the cyanide. The most common oxydant is the chlorine, commercialized as gas or hypochlorite, needing approximately 1 Kg. of Ca (CIO)2 per Kg. of cyanide to destroy.