Due to the shortage of freshwater, seawater has been widely considered for mineral flotation. However, the presence of Mg2+ in seawater plays an apparently negative role. In this work, two dispersants (i.e., sodium silicate (SS) and sodium hexametaphosphate (SH)) were applied to reduce the detrimental effects of Mg2+ on the flotation of molybdenite (MoS2). Various measurements including contact angle, zeta potential, FTIR and XPS were carried out to understand the impacts of these two dispersants on MoS2 flotation. Results indicate that both dispersants prevented the adsorption of colloidal Mg(OH)2 onto MoS2 surface under alkaline conditions, thereby improving MoS2 floatability. In addition, both dispersants are physically adsorbed on MoS2 surface, but chemically adsorbed on Mg(OH)2 surface. In addition, the extended Derjaguin-Landau-Verwey-Overbeek (DLVO) calculation suggests that both SS and SH reverse the total interaction energies between MoS2 and colloidal Mg(OH)2 from negative (attraction force) to positive (repulsive force), with the impact of SH being more significant.
This journal is © The Royal Society of Chemistry.