Investigating the role of pulp chemistry on the floatability of a Cu–Ni sulfide ore

This study investigated the effect of the pulp chemistry conditions during milling on the flotation performance of an Nkomati ore. The results have shown that there was approximately 10% increase in Ni recovery, when the ore was ground at dissolved oxygen (DO) concentration of 0 ppm in comparison to a condition where oxygen was allowed to access the slurry during the grinding stage. However, when the pH was changed from 9 to 11, the presence of oxygen resulted in a 20% decrease in the Ni recovery as compared to only 5% decrease in the Ni recovery at DO = 0 ppm. A noteworthy observation is that controlling a combination of DO and pH during grinding can have a significant effect on selectivity in the flotation of such ores. It was shown that grinding at lower DO levels/redox potentials (Eh) in the presence of xanthate significantly improved the recoveries of pentlandite and pyrrhotite.

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► The recovery of Cp was independent of both DO and pH.
► The recovery of Pn and Po were lowest when the ore was ground at DO=6.5 ppm.
► The recovery of Pn and Po decreased with increasing pH.
► Po recovery decreased significantly at DO=1 ppm, however Pn recovery only marginally decreased at the same DO concentration.
► There was no correlation between Eh measurements and the recoveries of the sulphide minerals.