Dissolution Rates of Au from Au–Zn Compounds Measured by Channel Flow Double Electrode Method

Abstract

Anodic dissolution rates of Au and Zn from Au–Zn compounds ( and ) in hydrochloric acid were measured by channel flow double electrode method. Simultaneous dissolutions of Au and Zn were observed at potentials above from . The dissolution rate of Au from the compound at was about 10 times higher than that of pure Au. On the other hand, Zn dissolved preferentially from at all tested potentials between 0.1 and , and Au started to dissolve at around . Chronoamperometry at showed that dissolution of Au from was slower than that of pure Au at the earlier stage, but it accelerated gradually and eventually became faster than the dissolution of pure Au. An Au-enriched layer consisting of and Au was generated with cracks at the compound surface during dissolution, and this morphological change explained the time variation of the dissolution rate. A more effective enhancement of Au dissolution was observed in than in . The result demonstrated the effectiveness of a Zn vapor pretreatment for leaching of Au.