| Abstract:
Feasibility of extraction of silver from tailing dam of Ahangaran mine was investigated by various leaching reagents including sulfuric acid, nitric acid, hydrochloric acid and sodium cyanide. The influence of mineral acids concentration indicats that the maximum silver recovery is obtained with 6 M hydrochloric acid, 4 M sulphuric acid and 5 M nitric acid and at leaching time of 80 min. The further increase in sulfuric and hydrochloric acid concentrations had no considerable effect on the increment of silver recovery. The role of H2O2 as oxidant agent was also evaluated on silver recovery. The results demonstrated that the most silver recoveries by sulphuric acid obtained at 2 M H2O2, and thereafter recovery reduced with increasing the H2O2 concentration. In addition, statistical design of experiments was used to evaluate the influential factors in the silver recovery using sodium cyanide. The findings indicated that among main factors, solid percentage and among interactions, interactive effect of solid percentage and pH had the most influence on silver extraction rate. The maximum silver recovery (58. 16 %) using sodium cyanide was achieved under following conditions: the pH ~11, solid percentage of 20, particles size of 75 μ m (200 mesh), 0. 1185 g/t NaCN, and leaching time of 4 h.
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