Effects of oils and lubricants on the flotation of copper sulphide minerals

The effects of the addition of oils and lubricants commonly encountered in mining and processing copper sulphide ores on the subsequent flotation of copper minerals was investigated by laboratory scale testing. The project arose as a result of intermittent uncontrollable frothing and a drop in selectivity observed at an Australian copper-gold concentrator. The addition of distillate to the grinding stage actually increased selectivity in the subsequent copper mineral flotation but other oils and lubricants used at the plant had detrimental effects on selectivity and frothing behaviour. A degreaser used in maintenance operations dramatically lowered copper grade and generated a very stable and sticky froth even at low concentrations. Similar detrimental effects on gold metallurgy were also observed. Mineralogical examination of flotation products verified that the decrease in grade of the concentrates was due to the flotation of free gangue minerals and not due to any liberation problems. Possible mechanisms for these effects aer discussed. Anecdotal evidence for these effects abound in discussions held with plant metallurgists, but little published data on these effects have been located.