Process for leaching zinc from partially desulfurized zinc concentrates by sulfuric acid

A process for the treatment of an iron-containing zinc sulfide material in the form of an ore or concentrate, which comprises:

• contacting said iron-containing zinc sulfide material with an oxidizing gas at a temperature below the sintering temperature of said material to remove up to about 60 percent of sulfur-sulfide in said material and thereby to form a partially-desulfurized zinc-bearing sulfide material containing zinc oxide, ferrous iron oxide and unconverted zinc sulfide,
• selectively leaching said material with a sulfuric acid-containing solution at a temperature of about 80.degree. C. up to the boiling point of the solution to dissolve thereby preferentially said zinc oxide over said ferrous iron oxide and said unconverted zinc sulfide to provide a first leach solution and a first leach residue containing said ferrous iron oxide and said unconverted zinc sulfide,
• selectively leaching said first leach residue with sulfuric acid at a temperature of at least about 70.degree. to dissolve thereby preferentially said ferrous iron oxide over said unconverted zinc sulfide to provide a second leach solution and a second leach residue containing said unconverted zinc sulfide, and
• recycling said unconverted zinc sulfide to said contacting step.