Effect of serpentine and sodium hexametaphosphate on ascharite flotation

Sodium hexametaphosphate (SHMP) was used to minimize the adverse effect of serpentine for improving ascharite recovery. The effects of particle size and content of SHMP, and serpentine on ascharite flotation process were investigated through flotation, zeta potential tests, FT-IR analysis, XPS analysis and DLVO theory. Particles interaction and mechanism of SHMP were also discussed. It was found that aggregation between serpentine and ascharite particles easily happened, and the particle size of serpentine had a profound impact on the ascharite recovery. In particular, the fine serpentine with size less than 38 μm had the greatest contribution to the deterioration of ascharite flotation performance. After SHMP treatment, the adverse effect of serpentine was significantly reduced. The mechanism of SHMP showed that it could alter the surface charges of serpentine and ascharite to prevent severe interparticle aggregation, which resulted in a well-dispersed pulp and benefited ascharite flotation process. The adsorption of SHMP on serpentine was due to hydrogen bonding and chemical adsorption, resulting in the formation of complex on serpentine surface to decrease its floatability.