Residual Dewatering Aids in Process Water on the Depressant Adsorption and Zeta Potential of Plagioclase

The separation of sulfide minerals from non-sulfide gangue minerals using froth flotation necessitates the utilisation of thickeners and filters to dewater concentrates and tailings. To facilitate the dewatering of flotation products, namely, concentrates and tailings, chemical reagents such as flocculants and coagulants are utilised in thickeners to increaseefficacy. However, residual amounts of these chemical reagents can be found in the clear supernatant and filtrate resulting from the dewatering process. Considering that the water recovered from dewatering unit operations is recycled back into milling and flotation, it is crucial to understand how the chemistry of these dewatering chemical agents may impact the behaviour of the pulp phase. Possible interactions may occur at the mineral surface between the flotation reagents, residual flocculants/coagulants, and inorganic electrolytes present in the recovered and recycled process water. Surprisingly, there is a lack of information in the existing literature regarding the influence of flocculants and coagulants on the adsorption of depressants such as carboxy methyl cellulose onto non-sulfide gangue minerals. Therefore, the primary objective of this study was to investigate the impact of flocculants and coagulants on the adsorption of depressants onto non-sulfide gangue minerals using plagioclase as a proxy for the non-sulfide gangue typically present in sulfide mineral flotation. The results from the adsorption and zeta potential studies showed that the presence of a residual coagulant concentration in recycled water was favourable and increased the adsorption of CMC onto plagioclase. However, the presence of a flocculant in recycled water may be detrimental as CMC adsorption onto plagioclase significantly decreased. This implies that sulfide mineral flotation plants which recycle and reuse water from dewatering processes may need to carefully monitor and control residual dewatering aids in recycled water as these species may have a significant bearing on flotation performance.