Calcium and sulfate Ions on flotation performance of a Cu-Ni-PGM ore in the presence of anionic polyacrylamide and carboxymethyl cellulose

The concentration of PGM ores through froth flotation is a water-intensive process, and with increasing global concerns about water scarcity, recycling process water in mineral processing plants has become essential. However, recycled water often contains deleterious ions and residual reagents that may alter mineral surfaces, pulp chemistry, and reagent action, impacting flotation performance and tailings dewatering. This study investigates the effects of calcium (Ca²⁺) and sulfate (SO₄²⁻) ions on flotation performance and tailings dewatering in the presence of CMC and PAM, using a Cu-Ni-PGM ore from the Merensky reef. Batch flotation tests showed that solids and water recoveries increased and then decreased with higher Ca²⁺ concentrations in the presence of CMC. PAM, however, resulted in steady water recoveries and slightly decreased solids recoveries with Ca²⁺ spiking, suggesting PAM’s action overrides ionic effects. SO₄²⁻ spiking slightly increased water and solids recoveries with CMC, while with PAM, it showed minimal influence on water recovery but a slight decrease in solids recovery. Tailings settling rates decreased with higher Ca²⁺ concentrations for PAM but increased initially for CMC before decreasing. SO₄²⁻ spiking improved settling rates for both polymers, this is attributed to induced coagulation of naturally floatable gangue. Overall, tailings settled faster with PAM than with CMC.