A kinetic study of the cementation of gold from cyanide solutions onto copper

The kinetics of cementation of gold onto copper was evaluated using a copper rotating disc and suspended particles systems. It was found that the cementation of gold onto copper is controlled by a kinetic step. For both rotating disc and suspended particles systems, the effects of temperature, cyanide and gold concentration on the rate of cementation are more significant than those of rotation speed and solution pH. The kinetic rate constant of cementation of gold onto copper is comparatively smaller than those found for the gold-zinc-cyanide or silver-copper-chloride systems. The activation energy was found to be 53.4 and 54.1 kJ/mol for copper rotating disc and suspended particles, respectively, which values are close to the measured value of 56.9 kJ/mol found in the electrochemical study. The morphology of the deposits, determined by Field Emission Scanning Electron Microscope, confirmed observations from experimental measurements, showing the passivation or acceleration of cementation due to the different types of deposit formed.