The formation of iron sulphide on oxidised pyrite during sulphidisation and subsequent interactions with xanthate

Abstract

Pyrite can be partially or completely oxidised during the stockpiling of pyritic ores, leading to a poor flotation performance. Sulphidisation with potential control has been commonly practised to convert the oxidised pyrite surface into a sulphide form before flotation. However, the lack of agreement on the suitable potential for the formation of iron sulphide species on the oxidised pyrite surface makes this practice genuinely uncertain. Using electrochemical techniques, this work identified that it was only at a potential below −300 mV that the sulphidisation with Na2S could generate iron sulphide species on the oxidised pyrite surface. In order to have the newly sulphidised pyrite surface to react with xanthate, the potential had to be elevated to 100 mV, but the newly formed iron sulphide species started to oxidise at a potential of around −50 mV. These findings provide a fundamental understanding of the nature of sulphidisation of oxidised sulphide minerals and a guideline to improve their flotation.