Modeling the cyanide heap leaching of cupriferous gold ores - Part 1: Introduction and interpretation of laboratory column leaching data

A kinetic and thermodynamic model of cyanide heap leaching of copper-bearing gold ores was developed in order to facilitate the evaluation and treatment of these complex ores [F. Coderre, Modeling the cyanide heap leaching of cupriferous gold ores. M.A.Sc. Thesis, U. British Columbia, 1998.]. In this first paper on the work, the behaviour of copper minerals in cyanide solutions is reviewed, and data from a series of laboratory column leaching tests performed under different influent cyanide concentrations are presented and interpreted in support of model development. The cyanide leaching is shown to occur in four distinct stages: (1) reductive dissolution of Cu(II) salts, during which copper and gold precipitate as cyanide salts, and no gold appears in the column effluent; (2) redissolution of the copper and gold cyanide precipitates; (3) leaching of copper sulphide minerals and elemental gold; and (4) free cyanide breakthrough in the effluent, which is accompanied by the appearance of dissolved iron from the redissolution of metal hexacyanoferrates, During the leaching step, it appears as if elemental gold dissolves in the absence of free cyanide, but that the copper sulphides do not. (C) 1999 Elsevier Science B.V. All rights reserved.