Recovery of metals

The process for recovering copper from a finely ground primary copper concentrate containing copper and iron in the form of sulfides, comprising slurrying said concentrate in an aqueous solution containing ammonium sulfate and free ammonia so proportioned as to maintain the pH of the slurry from about 9 to 11 and agitating the resulting slurry with a vigor input of at least 0.05 horsepower per cubic foot at a temperature in the range from 50.degree. C. to 80.degree. C. and at or near atmospheric pressure in the presence of free oxygen while recirculating said oxygen from above the surface of said slurry to a depth below such surface, the amount of ammonia utilized being correlated with the temperature so that the combined water vapor and ammonia partial pressures are at least a few psi below the total pressure of the system and the oxygen partial pressure makes up substantially the balance of the total pressure, terminating the leaching operation while an appreciable proportion up to about 50% of copper sulfide remains undissolved in the residual solids, withdrawing from the leaching operation slurry containing copper in dissolved form complexed with ammonia in the aqueous phase and mineral matter containing undissolved sulfides in the solid phase, separating the aqueous leach solution from the residual solids containing the remaining copper, subjecting said residual solids to a secondary flotation concentration operation to produce a secondary sulfide concentrate substantially smaller in amount than the primary concentrate containing copper which has passed through the leaching operation undissolved and to reject in the tailings of said secondary flotation operation iron sulfide of the primary concentrate which has been freed by the leaching operation from copper, and recovering from said secondary concentrate.

The process for recovering copper from a finely ground primary copper concentrate containing copper and iron in the form of sulfides, comprising slurrying said concentrate in an aqueous solution containing ammonium sulfate and free ammonia and agitating the resulting slurry with a vigor input of at least 0.5 horsepower per cubic foot at a temperature in the range from 50.degree. to 80.degree. C. and at a pressure up to 10 psig in the presence of free oxygen while recirculating said oxygen from above the surface of said slurry to a depth below such surface, the amount of ammonia utilized being correlated with the temperature so that the combined water vapor and ammonia partial pressures are at least a few psi below the total pressure of the system and the oxygen partial pressure is at least about 5 psi of oxygen in the atmosphere over the slurry, terminating the leaching operation while an appreciable proportion up to about 50% of copper sulfide remains undissolved in the residual solids, withdrawing from the leaching operation slurry containing copper in dissolved form complexed with ammonia in the aqueous phase and mineral matter containing undissolved sulfides in the solid phase, separating the aqueous leach solution from the residual solids, subjecting said residual solids containing the remaining copper to a secondary flotation concentration operation to produce a secondary sulfide concentrate substantially smaller in amount than the primary concentrate containing copper which has passed through the leaching operation undissolved and to reject in the tailings of said secondary flotation operation iron sulfide of the primary concentrate which has been freed by the leaching operation from copper, and leaching said secondary sulfide concentrate to recover copper therefrom.