| abstract |
Copper, zinc and nickel are recovered from sulfide concentrates prepared from ores of one or more such metals by subjecting such concentrate to a leaching operation which comprises slurrying the concentrate in an aqueous solution containing ammonium sulfate and free ammonia and vigorously agitating the slurry at 50 to 80° C. and below 10 psig. in the presence of free oxygen while vigorously recirculating said oxygen from above the surface of the slurry to a substantial depth below such surface. The resulting pregnant leach solution contains copper, zinc, and/or nickel in dissolved form complexed with ammonia and such solution is treated to recover the dissolved metal. The undissolved sulfidic residue from the leaching operation is subjected to a secondary flotation operation to produce a sulfide concentrate containing the metal values not dissolved in the leaching operation, and such concentrate is treated to recover such values, as by smelting or by releaching. |