Electrochemical study on copper cementation from cyanide liquors using zinc

A rotating-disc electrode system was used to study the half-cell reactions involved in the cementation of copper from cyanide liquors onto zinc. Using scanning voltammetry, the reduction of copper cyanide onto glassy carbon and copper discs and the oxidation of zinc from a zinc disc were evaluated at different conditions of solution pH, temperature and free cyanide concentration. Evans diagrams were constructed yielding mechanistic information and rate of the cementation process. Thermodynamic modelling of the copper cyanide system also predicts the electrochemical active species responsible for the reduction of copper cyanide as Cu(CN);. The study allows optimised conditions to be chosen for the selective recovery of gold from copper-gold cyanide mixture using zinc powder cementation. (C) 1999 Elsevier Science Ltd. All rights reserved.