New insights into the beneficial roles of dispersants in reducing negative influence of Mg(2+) on molybdenite flotation

Due to the shortage of freshwater, seawater has been widely considered for mineral flotation. However, the presence of Mg(2+) 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 Mg(2+) on the flotation of molybdenite (MoS(2)). Various measurements including contact angle, zeta potential, FTIR and XPS were carried out to understand the impacts of these two dispersants on MoS(2) flotation. Results indicate that both dispersants prevented the adsorption of colloidal Mg(OH)(2) onto MoS(2) surface under alkaline conditions, thereby improving MoS(2) floatability. In addition, both dispersants are physically adsorbed on MoS(2) 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 MoS(2) and colloidal Mg(OH)(2) from negative (attraction force) to positive (repulsive force), with the impact of SH being more significant.