A study of the relative adsorption of guar onto pure minerals

The aim of this study was to investigate the adsorption of guar gum onto talc, pyroxene, plagioclase, chromite and chalcopyrite and mixtures of talc with each of the other four minerals. These minerals commonly occur in the Merensky and UG2 ore bodies of the Bushveld Complex in South Africa, which is host to much of the world’s platinum group minerals (PGMs). Zeta potential measurements were conducted to establish differences in surface charge between a pH of 2 and 10. At pH 9, the pH of most PGM flotation operations, plagioclase had the most negative surface charge, followed by talc, chromite and pyroxene whose surface charges were very similar. Chalcopyrite had the least negative surface charge. On the basis of the observed surface charges and in terms of classical acid–base theory, guar was expected to have the strongest interaction with chalcopyrite and the weakest with plagioclase. Equilibrium adsorption studies confirmed that in a buffered solution, chalcopyrite had the highest affinity for guar, followed respectively by talc, chromite, pyroxene and plagioclase. Results of studies to evaluate the relative adsorption of each mineral in a mixture with talc showed that guar adsorbed preferentially onto chalcopyrite, pyroxene and chromite, in that order, rather than onto talc. Talc however, preferentially adsorbed guar when in a mixture with plagioclase. The ramifications of these findings for the operation of PGM flotation plants are discussed.