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

摘要

Copper is recovered as its sulphide by treating a copper-bearing material, e.g. a raw ore or a concentrate, with an aqueous solution of a cyanide e.g. NaCN, KCN, Ca(CN)2, or mixtures of these, or an organic a -hydroxynitrile e.g. lactonitrile, for a period of less than 4 hours at a molar ratio of at least 3 cyanide to 1 Cu preferably 3-4: 1, and by treating the Cu-containing solution thus formed with less than a stoichiometric amount, in general 10-65% of the theoretically required amount, of a soluble sulphide e.g. H2S, Na2S, NaHS, Ca2S, CaHS sodium or calcium sulph-hydrate or an ammonium sulphide, acidifying to sT pH 5 with e.g. H2SO4 or HCl, and collecting on the one hand, HCN, which may be neutralized with CaO and on the other, copper sulphide precipitate, which may be purified or smelted directly. In an alternative method the soluble sulphide and acid are added simultaneously.