Metal sulphide extraction

A process for recovering non-ferrous metal values from a metal-containing sulphide material containing at least one non-ferrous metal selected from zinc, copper, lead, cobalt, nickel, silver and gold, as well as iron comprising leaching the complex sulphide material under an oxygen partial pressure in the range of from about 50 psig to about 250 psig (about 345 kPag to about 1725 kPag) and at a temperature in the range of from about 50.degree. C. to about 250.degree. C. in a leach stage with an acidic aqueous chloride lixiviant solution containing magnesium chloride and having a chloride ion concentration of at least 2 gram ions per liter, thereby to solubilise non-ferrous metal values in the material and to leave a residue comprising iron in oxide or hydrated oxide form and also sulphur, controlling the pH of the leach liquor from the oxidative leach step at a value of between about 0.5 and about 2.5, passing resulting non-ferrous metal-containing leach liquor to a metal recovery section including one or more cementation stages and a solvent extraction stage in which non-ferrous metal values are recovered by liquid-liquid extraction from a zinc chloride-containing liquor at a pH in the range of from about 1.5 to about 4.0 using a hydrophobic organic extractant phase containing a magnesium salt of a cationic transport agent for zinc, recovering from the solvent extraction stage an aqueous magnesium chloride-containing raffinate and a zinc-loaded organic phase, subjecting a portion of the aqueous magnesium chloride-containing raffinate from the solvent extraction stage to high temperature hydrolysis, thereby liberating hydrogen chloride and magnesium oxide, recycling another portion of the aqueous magnesium chloride-containing raffinate to the leach stage, recycling liberated hydrogen chloride to the leach stage, passing magnesium oxide formed in the high temperature hydrolysis to the solvent extraction stage for use as neutralising agent for the cationic transport agent, subjecting zinc-loaded organic phase from the solvent extraction stage to stripping with an aqueous sulphuric acid strip liquor, electrolysing resulting zinc-loaded strip liquor, recovering resulting metallic zinc, and passing a part of the recovered metallic zinc to the cementation stage or stages.