Electrocoagulation Process for Recovery of Precious Metals from Cyanide Leachates Using a Low Voltage

The cyanidation of gold ores with copper content is frequent in gold mines. Copper affects the performance and profits of mineral processing. The current technology for gold recovery from cyanide solutions usually involves the adsorption of the gold-cyanide complex ion on activated carbon; however, the copper affects this process. The process of electrocoagulation (EC) is a promising technique for gold and silver recovery with copper, where all of the metals can be recovered. This work used the electrocoagulation process (EC) to evaluate the metal recovery from a pregnant leach solution (PLS), where EC is a promising technique. This study aimed to determine the optimal parameter to recover the gold and silver and to see the effect of copper concentration in the PLS obtained by simultaneous pressure leaching/oxidation of a gold-bearing pyritic concentrate. EC tests were run to recover gold and silver over copper from PLS using aluminum electrodes and variables like distances between electrodes, pH, potential applied, and feeding flow for continuous EC. The chemical assay of cyanide leachates shows a concentration of 7.15 mg/L of gold, 305 mg/L of silver, and 351.5 mg/L of copper with 1810 mg/L of free cyanide. The results showed that the EC process recovered 99% of gold and copper and 92% of silver at a pH of 11, 8 mm of dE, and a potential applied 3 V in 10 min. However, under this condition in continuous EC with a flow rate of 40 mL/min, the recovery is 66.3% of gold, 85.8% of silver, and 45.3% of copper; compared with the batch process, the gold and silver decrease.