Fundamental kinetic models for gold ore cyanide leaching

Abstract

Existing studies of gold ore cyanidation kinetics demonstrate significant diversity in estimated kinetic parameters. By taking into account the size distribution of gold grains in the ore it was made possible to explain this diversity and the apparent "homogeneous" behaviour of the heterogeneous particles. A variable order kinetic equation successfully fitted data on different types of gold ores previously published by other investigators. Furthermore, two previously established fundamental kinetic equations, both based on the electrochemistry of pure gold cyanidation, were adopted for gold ores and incorporated into the variable order kinetic equation. The first equation was derived from the theory of mixed potentials, while the second was based on Habashi's cyanidation model. Both kinetic equations demonstrated good accuracy in predicting the dependence of the gold extraction rate on the concentrations of free cyanide and dissolved oxygen. The Habashi equation employs fewer parameters than the other and, therefore, is more suitable when there is a lack of experimental data. Parameters for both kinetic equations have been estimated by fitting them to experimental data collected previously.