Residual Dewatering Aids in Process Water on Flotation Performance of a Selected Cu-Ni-PGM Ore from a Siliceous Reef

Abstract

The increasing scarcity of water has led to mine operations recycling water from tailing dams, thickener overflow, dewatering and filter products. However, water quality is found to influence the process of ore flotation, with adverse effects on flotation selectivity. The adsorption of the collector onto valuable minerals may also be affected by the unintended change on water chemistry. This study simulates the impact of dewatering reagents present in recycled water from tailings dewatering unit operations into the flotation process using a Silicate reef ore from the South African Bushveld Igneous Complex (BIC) supplied by Pilanesburg Platinum Mines. Unique plant water (UPW), consisting of inorganic electrolytes and dewatering chemical reagents, was synthetically prepared using water quality analyses received from a South African concentrator processing a Cu-Ni-PGM bearing Merensky ore. The study has a specific focus on the impact of flocculants and coagulants as dewatering reagents present in recycled process water on solids recovery, water recovery, copper and nickel mineral recovery, copper and nickel mineral grade, residual concentrations of the collector post flotation are also determined as well as particle settling of the tails after flotation. The results show that the presence of dewatering reagents in recycled process water into the flotation system may result increased mineral particle recoveries, both the valuable minerals and gangue. However, the increase in gangue recoveries may be to the detriment of the concentrate grades with respective to the valuable minerals of interest. The ability to pull more solids to the concentrate could further have considerable implications on the dewatering of tailings post flotation as each condition resulted in distinct tailings settling tendency. It was also shown that there was little to no influence on the adsorption of the freshly dosed collector as its residual concentrations in the tails remained fairly the same across the tested process water conditions containing residual concentrations of the coagulant, depressant and flocculant.