The roles of complexing agents in the sulfidisation and xanthate flotation of cobalt oxy hydroxides of copper-cobalt oxides ores from the Congolese Copperbelt

Complex mineralogy combined with a variable chemistry lead to various flotation responses of cobalt oxy-hydroxides present in oxidised and mixed copper-cobalt stratiform deposits of the Central African Copperbelt. Optimum metallurgical results require very high dosages of reagents and the management of such high chemicals concentrations in the pulp at the plant scale is delicate. The transition period between high reducing conditions during the sulfidisation step and a more oxidising environment prevailing during collector adsorption is particularly critical.
This paper demonstrates how the use of copper and cobalt complexing agents can significantly improve the process control and metallurgical performance. The different modes of action of these reagents are presented and mechanisms for the various reactions proposed. Plant results following the introduction of ammonium sulfate at the New Concentrator of Kipushi are discussed.