Low acidity, low solids pressure oxidative leaching of sulphidic feeds

摘要

Process for recovering one or both of copper and silver from a sulphidic feed containing iron, arsenic, copper and silver by pressure oxidizing an aqueous feed slurry of the sulphidic feed in a pressure vessel to form a liquid phase containing free sulphuric acid and aqueous copper sulphate, and to precipitate arsenic as solid iron arsenic compounds. The process includes operating the pressure vessel at a sufficiently low solids content to maintain a free acid level below 30 g/L in the liquid phase, and providing sufficient heat to maintain a temperature in the pressure vessel above 200° C. Copper metal is recovered from the liquid phase and/or silver may be recovered from the solids by cyanide leaching without the need for a jarosite destruction step.