EJMP&EP





The role of cyanide in the multi-component elution of cyanide complexes from activated carbon

J.S.J. van Deventer*, S.P. Liebenberg

Department of Chemical Engineering, The University of Melbourne, Victoria 3010, Australia


Received 6 December 2001; accepted 13 December 2002




ABSTRACT

At high temperature and with cyanide pretreatment the elution of metal cyanides from activated carbon in a column is independent of flow rate. Therefore, an equilibrium model based on the multi-component Freundlich isotherm could be used to simulate the competitive desorption of gold and copper cyanides from activated carbon. The elution profiles of free cyanide and the spectator cation had to be modelled as a precursor to the modelling of elution profiles for the metal cyanides. The dependence of the desorption equilibrium parameters on cyanide pre-treatment also had to be considered. In the model for the removal of free cyanide the rate of the cyanide destruction in the bulk solution was included by combining the hydrolysis and oxidation reactions that revealed first order kinetics. The rate of cyanide decomposition in the carbon pores was assumed to change with the amount of cyanide already decomposed at a specific temperature. It was also important to consider the dependence of equilibrium parameters on the concentration of spectator cations. The introduction of a competition coefficient adequately described the competitive effect of copper on gold elution profiles.


Keywords: Gold; Copper; Cyanide; Elution; Modelling



* Corresponding author
   E-mail : jannie@unimelb.edu.au