Copper activation option for a pentlandite–pyrrhotite–chalcopyrite ore flotation with nickel interest

Abstract

Different sulphide ores respond differently in the prospect of copper activation to thiols for froth flotation. With the BCL Selebi-Phikwe ore body, pentlandite–pyrrhotite–chalcopyrite co-occur and there is the constraint of fine pentlandite dissemination in the pyrrhotite, so that liberation is limited. In the presence of pentlandite, pyrrhotite can even be galvanically depressed. In this scenario, response of the ore to copper activation may not be easily predicted. To explore the possibilities, flotation with various dosages of copper addition was investigated for this ore with specific interest in how the nickel recovery responds. The responses of copper, iron, cobalt and quartz were also monitored. Increase in nickel recovery and grade with copper sulphate dosage was obtained, compared with no addition, but the trend showed a maxima after which depression was obtained. The optimum dosage in this instance was between 15 and 30 g/ton for best grade recovery. The response is understandable from the fact that the predominant copper species in the aqueous system can be ion or hydroxide depending on the concentration, among other factors. As ions the copper thus imparts activation, while as hydroxide it will cause depression. Pyrrhotite and chalcopyrite recovery also increased marginally along with the pentlandite. To achieve activation of pentlandite in the ore to thiol collector using copper sulphate, the dosage must be about the optimum; higher dosages will bring about depression.