Effect of solution chemistry on the flotation system of smithsonite and calcite

Both smithsonite and calcite are calcite-group minerals which are isomorphous with one another. They are similar in many physical and chemical properties, and may partially or fully replace one another, which make the separation of smithsonite from calcite inefficient and ineffective in flotation. The present study was undertaken to investigate the solubility properties of individual calcite and smithsonite minerals and their mixtures, and establish correlation between solution chemistry and flotation behavior. Solution chemical calculations show that the species distribution of smithsonite and calcite was strongly affected by solution pH value. With the increase of pH, the measured solubility of calcite is very close to the theoretical value, while that of smithsonite is less than the theoretical value, illustrating that surface precipitations of zinc hydroxide and hydrozincite are possible. In the mixed system, solution chemical calculations show that the conversion from smithsonite and calcite to hydrozincite and zinc hydroxide is spontaneous. The flotation behavior of smithsonite and calcite was studied with the supernatants, and XPS analysis was conducted to detect surface properties. Both simulation results and experimental data show that surface conversion from calcite to zinc species has a vital influence on the separation of smithsonite from calcite by flotation.

► Zinc hydroxide and hydrozincite produce on smithsonite surface.
► The dissolved species of calcite have little effect on smithsonite flotation.
► Surface conversion from calcite to zinc species can be spontaneous.
► Surface conversion plays a vital role on the separation of smithsonite from calcite.