OPTIMIZING THE OPERATING CONDI TIONS OF GOLD ELUTION AND ELECTROWINNING FOR TAU LEKOA STREAM AT KOPANANG GOLD PLANT

The final gold product of Tau Lekoa mine has a low fineness, primarily due to the high concentration of base metals in the reefs. These metals, when leached with cyanide, can contaminate the gold during the electrowinning process if not adequately controlled. This study aimed to optimize the operating conditions for gold elution and electrowinning. Four parameters were evaluated: temperature, flow rate, free caustic soda concentration, and cyanide strength. Experimental runs on a plant scale demonstrated that the first three parameters significantly impact the retention of base metals in carbon during elution, thereby improving the final product's fineness from 80% to 84%. Furthermore, a thermodynamic model was developed to examine the competition between gold and nickel deposition during electrowinning, revealing that their deposition is dependent on concentrations and temperature. The improvements in the single pass efficiencies and deposition rates resulted in a further increase of product fineness to 85%. Improved fineness translates to higher gold content in the bullion and reduced impurities, which effectively lowers refining costs.