An Investigation of Copper Recovery from a Sulphide-Oxide Ore with a Mixed Collector System
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Current copper deposits contain significant amounts of secondary non-sulphide minerals and newly discovered deposits are increasingly complex. As a result, research into the improvement of sulphide-oxide copper ores processing through the use of mixed collector systems has surged. The flotation of a natural porphyry copper ore with bornite and malachite was investigated via fundamental work with pure minerals and a bench-scale testing regime. The processing of the test ore was problematic due to a mineral assemblage that caused prevalent slime generation. Fundamental adsorption, micro-flotation and Eh-pH tests were conducted on pure minerals to investigate mineral-collector behaviours. PAX and hydroxamate form multiple collector layers on malachite and bornite, with malachite and hydroxamate exhibiting the highest adsorption density. The effective pH range of the collectors was pH 8-10 where the collector species, according to equilibrium species distribution diagrams, were Cu(HXM)2 (aq) and CuEX (s) for hydroxamate and xanthate respectively. A Box-Behnken response surface design was used to determine collector dosages that provide an optimum flotation response for the natural ore. The collectors were: potassium amyl xanthate (PAX), Cytec Promoter 6494 hydroxamate and DETA. The copper recovery, malachite recovery, minor copper recovery and copper grade responses were optimized using JMP statistical software. Indicators of model inadequacies were noted but since the models predicted sensible solutions, inaccurate test ratios and un-modeled effects were hypothesized to be the source of the inadequacies. The model predicted 98 % copper recovery using 202.7g/t PAX, 674.99 g/t hydroxamate and 61.9 g/t DETA. The copper grade model predicted an the overall copper grade of 19% using with 0 g/t PAX, 167 g/t hydroxamate and 101 g/t DETA.