Copper(II) activation and cyanide deactivation of zinc sulphide under mildly alkaline conditions

The adsorption of copper(II) ions onto zinc sulphide particles at pH 9 was determined by inductively coupled plasma atomic emission spectrophotometry and the resulting surfaces were characterised by X-ray photoelectron spectroscopy. The form of the copper(II) activated zinc sulphide surface is controlled by the copper(II) ion concentration and the activation time. Copper(II) activation, at an equivalent surface coverage of one monolayer, results in a copper-substituted zinc sulphide surface, whereas at surface coverages of ten or more equivalent copper(II) monolayers a copper(II) hydroxide surface phase covers the underlying copper-substituted zinc sulphide phases. Mechanisms are proposed which describe copper(II) activation in terms of precipitation, ion-exchange, redox and diffusion processes. Cyanide treatment removes copper hydroxide and copper-substituted species from the surfaces of copper(II) activated zinc sulphide. Ligand exchange mechanisms for cyanide deactivation of copper(II) activated zinc sulphide are proposed.