LEACHING KINETICS AND MECHANISMS OF SURFACE REACTIONS DURING CYANIDATION OF GOLD IN THE PRESENCE OF PYRITE OR STIBNITE

摘要

This paper quantifies the detrimental effects of pyrite and stibnite ongold leaching kinetics. Means to reduce the effect of these minerals byaddition of lead nitrate and oxygen are presented. A significant retardingeffect was observed when the pyrite concentration was 20%. A pretreatmentwith lead nitrate reduced the extent of gold surface coating by Ag,Fe and S. Stibnite, at a concentration as low as 20 ppm, significantlyaffected the gold leaching kinetics through forming a passivating filmof Sb(V) oxide possibly Sb_2O_5. The most practical way to alleviate theeffect of stibnite is to leach the materials at a moderate pH with additionof lead nitrate. A low temperature reduced the efficiency of lead nitrate tocounteract the effect of stibnite. The increase of dissolved oxygen is notfavourable to alleviate the coating of stibnite on gold.