Adsorption, electrokinetic and differential flotation studies on sphalerite and galena using dextrin

Abstract

Adsorption, electrokinetic and flotation studies have been carried out to investigate the interaction of dextrin with sphalerite and galena. The adsorption density of dextrin onto sphalerite increases with increase of pH up to pH 7.5, and thereafter decreases, while that onto galena shows a maximum around pH 11.5. It is observed that the adsorption density of dextrin onto galena is quite high compared to that on sphalerite. Both the adsorption isotherms exhibit Langmuirian behaviour. Electrokinetic measurements reveal that the isoelectric points of sphalerite and galena are located around pH 3. The electrophoretic mobilities of both the minerals become less negative following polymer adsorption without any apparent shift in the isoelectric points. Dissolution experiments indicate release of metal ions from sphalerite and galena, while, co-precipitation tests confirm polymer–metal ion interaction in the bulk solution. Flotation tests show that dextrin effectively depresses galena in the pH range of 10 to 12 but not sphalerite, complementing the adsorption results. Differential flotation results indicate that sphalerite can be separated from its synthetic mixture with galena using dextrin as a depressant for galena at pH 12.1. Possible mechanisms of interaction between the two sulphide minerals tested and dextrin are discussed.