Dissolution of Gold with Bromine from Refractory Ores Preoxidized by Pressure Oxidation

Recovery of gold from refractory ores was studied by pressure oxidation as the method of ore pretreatment followed by bromination of oxidized residues. Three different ores were examined, Au-Ag, Au-Ag-Te, and Au-silver free ore. Pyrite was the major host mineral for gold in these ores. The effect of pressure oxidation parameters (temperature, pressure of oxygen, time, and pulp density) on subsequent bromination under standard conditions was examined. Bromination of residues produced under standard pressure oxidation conditions was examined as a function of: temperature, bromine and sodium bromide concentration, and time. Recovery of gold on activated carbon, from the pulp after bromination, was studied too. Recovery of gold from silver containing ores was lower (87-91%) than the recovery of gold from silver free gold ore (97%). In each studied case, the presence of activated carbon in the pulp further increased the recovery of gold.