Gold electrowinning from diluted cyanide liquors: performance evaluation of different reaction systems

This work deals with the performance of porous electrodes by using electrolytic cells with similar characteristics to the Zadraʹs one and with mechanical devices to increase the mass transport to the cathode. The flow-by configuration was the experimental arrangements used. Gold electrowinning was carried out with distinct cyanide solutions, namely: pure synthetic solution and synthetic solution with metallic impurities. This study aimed at investigating the effect of some parameters on the direct electrowinning of gold from cyanide solutions and a comparative study of two kinds of three-dimensional electrodes (stainless steel mesh and mild still wool). The current efficiency and the energy consumption were also analysed considering three competing cathodic reactions: gold deposition, oxygen reduction and hydrogen evolution. A mathematical model was also evaluated aiming at determining, experimentally, the mass transport coefficients considering the reaction systems under study.