Research Information System
IMCET 2019, Antalya, Turkey, 16 - 19 April 2019, pp.826-833
ABSTRACT
In this study, the effects of ultra-fine grinding (from 27 μm (d80, as-received) to 7.5 μm), cyanide concentration (2-5 g/L NaCN) and pulp density (30-50% w/w) on the rate and extent of extraction of gold and silver were studied. The tailings (d80=27 μm) used in the leaching tests contained 17.8 g/t Au, 99.5 g/t Ag, 6.4% Zn, 9.1% Fe and 560 g/t Cu. Dissolution of zinc, iron and copper was also monitored during the leaching tests. The findings demonstrated that, the tailings sample is highly refractory with low gold recoveries (i.e. 40.2% Au over 24 h.) in cyanide leaching (2 g/L NaCN). Reducing the particle size from 27 to 7.5 μm (d80) by ultra-fine grinding adversely affected the leaching performance in that the extraction of Au and Ag markedly decreased from 40.2% to 10.4% and from 67.3% to 54.4%, respectively, over 24 h. This could be attributed to the fact that fine grinding can increase pulp viscosity, surface area of sulphides and their possible activation. Copper dissolution was observed to be high (i.e. ≤62.2%). This could have also contributed to low gold/silver extractions due to the excessive consumption of cyanide through complexation with copper. The extraction of gold was shown to improve up to 73.0% by increasing the cyanide concentration or decreasing the pulp density.
Keywords: Gold/silver, tailings, cyanide leaching, refractoriness, ultra-fine grinding.