Water quality impact on flotation Response: A focus on specific ions and temperature

Abstract

Plant water recycling causes an accumulation of ions in the process water which may affect plant processes since processing routes are water intensive. Seasonal temperature differences affect the water quality through variation of the available recycled water within the plant between the summer and winter seasons. The objective of this study was therefore to investigate the effect of specific ions and temperature, relevant to onsite process water recycling and temperature variations brought about by seasonal changes, on the separation of gangue from valuable minerals in batch flotation of a low-grade Cu-Ni-PGE ore. Water and solids recoveries were impacted by Ca2+ and SO42-. At high SO42- concentrations, an increase in Ca2+ increased the mass of water and solids recovered. An increase in SO42- alone caused an increase in copper recovery whilst decreasing the copper grade. S2O32- alone affected the nickel recovery. An increase in S2O32- caused an increase in nickel recovery whilst the nickel grade was affected by the interaction of S2O32- and temperature. Furthermore, copper showed similar trends as those observed for nickel in the responses for the mineral grade. At high S2O32- concentration there was no observable change in the nickel and copper grades when temperature increased. At low S2O32- concentrations, an increase in temperature decreased the nickel and copper grades. In addition to the interactive effect of temperature and S2O32-, nickel was more temperature sensitive in comparison to copper. The study demonstrated that there are specific ion concentration ranges beyond which flotation performance was adversely affected and other ranges beyond which no observable effect on flotation was visible. Based on this understanding, it may be possible to predict the ideal operating conditions for the number of water recycles in a plant. The higher ionic concentrations and their corresponding ionic strengths resulted in a more stable froth in comparison to lower ionic concentrations and consequently an improvement in the recoveries.