CHARACTERIZATION AND ELECTROCHEMICAL ANALYSIS OF GOLD CEMENTATION FROM ALKALINE CYANIDE SOLUTION BY SUSPENDED ZINC PARTICLES

Recent research efforts on gold cementation from alkaline cyanide solutions have provided further information on the nature of cementation reactions. The experimental work reported herein includes the kinetics of gold cementation by suspended zinc particles and electrochemical measurements using rotating zinc disk electrodes. The reaction which was usually limited by film diffusion was studied as a function of such variables as gold concentration, temperature, sodium cyanide concentration and lead nitrate addition using suspended zinc particles. The critical effect of the cyanide concentration on reaction kinetics was observed. Of particular significance was a particle aggregation phenomenon which involved the rapid coalescence and growth of reacting zinc particles (45 μm) to aggregates exceeding several millimeters in size. Evidence of zinc passivation and anodic closure were found from electrochemical measurements and support the analysis of the suspended particle reaction kinetics. © 1990.