Time dependent wettability of mineral and metal surfaces in the presence of thiol surfactants

The decrease in wettability of mineral and metal surfaces due to the adsorption of surfactants is crucial for flotation recovery and upgrading of these materials in mineral processing. Because of limited residence time in flotation processing, the kinetics of the wettability changes of the mineral surface becomes an important issue. The time dependent wettabilities of silver and galena (PbS) surfaces in aqueous solutions of di-isobutyl dithiophosphinate, a commercial flotation reagent, were determined from in situ measurements of advancing and receding bubble contact angles. Kinetic parameters were calculated from these data. By comparing the in situ measurements with ex situ measurements of water contact angles and external reflection FTIR of the adsorbed organic films on silver, a physical interpretation of the wettability data is given in terms of the evolution of these thin organic films on the mineral surfaces.