Effects of stripping parameters on cyanide recovery in silver leaching operations

High cyanide concentrations are used for leaching ground silver ore at the Eti Gumus plant located at Kutahya, Turkey. In this study, stripping parameters for cyanide recovery by a process of Acidification, Volatilization and Re-neutralization (AVR) were investigated for the tailings from the plant, and optimal values of parameters were determined to assess the technical feasibility of the AVR process. A pilot plant was designed, constructed and run continuously for 14 days. Batch experiments were conducted to determine the effects of variables such as pH, aeration velocity, gas/liquid (G/L) ratio, ambient temperature and aeration (strip) time on NaCN recovery. Experimental pilot plant data indicated that a cyanide recovery of over 97% could be achieved using optimized conditions and the corresponding effluent concentration could be reduced to significantly less than the required maximum level of 50 mg/L NaCN.