Leaching of copper from ores with cyanide and recovery of copper from cyanide solutions

摘要

1,050,303. Recovery of copper; HCN. AMERICAN CYANAMID CO. Feb. 19, 1965 [Dec. 14, 1964], No. 7337/65. Heading C1A. Cu is recovered from a Cu-bearing material by leaching with an aqueous cyanide solution containing at least 3 moles CNSP1/SP to one mole Cu, for up to 4 hours at a pH of at least 9; treating the cuprocyanide Cu(CN) 3 SP11/SP solution thus formed with a stoichiometric deficiency of a water-soluble sulphide; and acidifying to a pH below 5, to ppt. CuS. Cu 2 Fe(CN) 6 and CuCNS which may result from the leaching are also pptd., the total amount of CNSSP1/SP, Fe(CN) 6 SP11/SP and SSP11/SP ions being stoichiometrically equivalent to the dissolved Cu. The HCN produced is stripped from the aqueous mixture, before or after solids separation, by heating, or by passing steam, air or N 2 through, and may be used directly, as a gas or aqueous acid, to leach an alkaline suspension of the raw material, or may be absorbed in Na, K or Li hydroxide, Ca oxide or hydroxide, or NH 3 , to give the corresponding cyanide, which is used for leaching. The use of organic -hydroxycyanides, e.g. lactonitrile is also referred to. The soluble sulphide may be H 2 S, Na 2 S, NaHS, NaSH, CaS or Ca(HS) 2 . The Cu solution may be separated from the gangue before sulphide treatment, or afterwards by flotation. Leaching, stripping and absorption of HCN are preferably carried out in countercurrent at ambient temperatures (5-40‹ C.) and pressures, absorption being effected with sprays, in stirred or baffled vessels, or in towers. The Cu bearing material may be an oxide or mixed oxide-sulphide ore or fines, slurries, tailings, concentrates, slags or sands from such ore.