Acid leaching pretreatment on two-stage roasting pyrite cinder for gold extraction and co-precipitation of arsenic with iron

The leaching recovery of gold is low caused by the arsenic inclusion and gold encapsulation in the two-stage roasting pyrite cinder. It is necessary to pretreat the cinder to improve the recovery of gold. In this study, sulfuric acid was employed to remove arsenic and iron from the cinder, and then the arsenic was transferred to precipitates from the leaching solution by ferric ion precipitation for harmless disposal. The vast majority of the arsenic and iron were leached into the solution at 80 °C under atmospheric pressure. The recovery rate of gold in residue after non-cyanide extraction was greatly improved, and the gold content in residue decreased from 11.2 g/t to 3.8 g/t. The leached iron was partly precipitated by controlling the additive amount of hydrogen peroxide and pH value to precipitate the arsenic. The arsenic concentration in the solution was reduced to about 5 mg/L after 1 h of precipitation. The size of the precipitates was increased to >100 μm when the pH value was >5.69. In addition, the precipitates had a strong adsorption capacity to absorb many other impurity ions such as ammonium. This study indicates that the removal of arsenic and iron from cinder is beneficial to increase the recovery of gold, and it is effective to remove the arsenic from the leaching solution through co-precipitation with ferric ion.