RECOVERY OF GOLD FROM AURIFEROUS REFRACTORY IRON- CONTAINING SULPHIDIC ORE

摘要

A process for recovering gold from refractory auriferous iron-containing sulphidic ore which comprises feeding ground ore as an aqueous slurry to an acidic pretreatment step. The ground ore in the acidic pretreatment step is treated with aqueous sulphuric acid solution to decompose carbonate and acid consuming gangue compounds which might otherwise inhibit a subsequent pressure oxidation step, and subjecting the treated slurry to a first liquid-solids separation step to produce a sulphate solution and separated solids. Water is added to the separated solids in a first repulping step to form a slurry having a pulp density in the range of from about 25 to about 60% by weight solids. The first repulped slurry is oxidized in a pressure oxidation step at a temperature in the range of from about 135 to about 250.degree.C under a pressurized oxidizing atmosphere while maintaining a free acid concentration of from about 5 to about 40 g/L sulphuric acid to cause dissolution of iron, formation of sulphuric acid and oxidation of substantially all oxidizable sulphide compounds to sulphate form with less than about 20% of oxidized sulphur being present as elemental sulphur during the oxidation step. Water is added to the oxidized slurry in a second repulping step to produce a repulped oxidized slurry with a pulp density in the range of from about 5 to about 15% by weight, and subjecting the repulped oxidized slurry to a second liquid-solids separation step to produce an acid and iron containing solution and oxidized separated solids. The acid and iron containing solution is recycled to at least one of the first and second repulping steps. The oxidized separated solids are washed with an aqueous wash solution in a washing step and the washed solids are separated from used washed solution containing acid and dissolved iron and non-ferrous metal sulphates in a third liquid-solids separation step. Used washed solution containing acid, dissolved iron and dissolved non-ferrous metal sulphates is recycled to the acidic pretreatment step, and gold is recovered from the washed solids.