Treatment of copper sulfide concentrates

A hydrometallurgical method of recovering copper from particulate copper sulfide flotation concentrate containing at least about 20% copper by weight comprised of cuprous and cupric sulfide, with sulfur present as sulfide sulfur, a significant portion of the copper in the copper sulfide concentrate being in the cuprous state,

• providing said copper sulfide flotation concentrate in the particulate state,
• subjecting said concentrate to leaching with an alkaline solution of ammonia plus ammonium sulfate of concentration ranging from about 30 gpl to 200 gpl of ammonia and about 25 gpl to 200 gpl of ammonium sulfate at a temperature ranging from about 10.degree. to 95.degree. C.,
• the amount of sulfide concentrate in said solution ranging from about 25 gpl to 500 gpl proportioned at least stoichiometrically to the ammonia concentration of the leaching solution,
• leaching said sulfide concentrate under substantially ambient pressure while continuously aerating said solution for a time at least sufficient to dissolve said cuprous copper and oxidize said cuprous copper to the cupric state while substantially minimizing the oxidation of sulfide sulfur to sulfate and thereby obtaining a pregnant filtrate containing at least about 15% of the total amount of copper in said concentrate and provide a washed residue containing at least about 20% of copper by weight comprised substantially of cupric sulfide,
• and then subjecting said residue to flotation to provide a second flotation concentration containing at least about 30% copper by weight,
• the copper in the leaching solution following further processing being subsequently recovered by electrowinning.

A hydrometallurgical method comprising a leaching operation for recovering copper from particulate copper sulfide flotation concentrate containing at least about 20% copper by weight comprised of cuprous and cupric sulfide, with sulfur present as sulfide sulfur, a significant portion of the copper in the copper sulfide concentrate being in the cuprous state or monovalent state, and thereby provide a copper sulfide-containing residue as a valuable intermediate which comprises:

• providing said copper sulfide flotation concentrate in the particulate state,
• subjecting said concentrate to leaching as a slurry with an alkaline solution of ammonia plus ammonium sulfate of concentration ranging from about 30 gpl to 150 gpl of ammonia and about 25 gpl to 200 gpl of ammonium sulfate at a temperature ranging from about 10.degree. C. to 95.degree. C.,
• the amount of sulfide concentrate in said slurry ranging from about 25 gpl to 500 gpl proportioned at least stoichiometrically to the ammonia concentration of the leaching solution,
• leaching said sulfide concentrate under substantially ambient pressure while continuously aerating said solution for a time at least sufficient to dissolve said cuprous copper and oxidize said cuprous copper to the cupric state short of oxidizing the contained sulfide sulfur and thereby obtain a pregnant filtrate containing at least about 15% of the total amount of copper in said concentrate and provide a washed residue as a valuable intermediate containing at least about 20% copper by weight comprised substantially of cupric sulfide,
• contacting said pregnant filtrate with an organic solvent dissolved in water immiscible liquid organic medium to extract copper therefrom and provide a copper-loaded organic solvent and an aqueous ammonia/ammonium sulfate raffinate substantially impoverished in said copper for recycling in the leaching operation, and
• treating said copper-loaded organic medium with an aqueous sulfuric acid solution to recover the copper as an acid copper sulfate solution of sufficient concentration for the recovery thereof by electrowinning and thereby to regenerate said organic solvent for reuse in the solvent extraction operation.