The effect of changes in pH on the depression of talc by chitosan and the associated mechanisms

Abstract

The depression effect of chitosan on talc as well as the associated mechanisms were investigated at different pH values. The flotation results showed that chitosan is a useful depressant for talc flotation and that its depression effect is independent of pH. The adsorption mechanisms of chitosan were different at pH3 and 9. X-ray photoelectron spectroscopy analysis indicated that at pH3 and pH9, the chitosan adsorbed on talc surfaces through physical interactions. At pH3, the adsorption changed the zeta potential of the talc from negative to positive and the adsorption was achieved via hydrogen bonding interaction. At pH9, in addition to adsorption due to hydrogen bonding, the water-insoluble chitosan also deposited on the talc surfaces and shifted the slip surface of the electric double layer outward, thus making the surface potential of the talc gradually approach zero. The adsorbed chitosan could be washed away from the surface. This phenomenon occurred more easily at pH3, because the deposited chitosan dissolved and entered the aqueous phase again. Flotation separation tests on the mineral mixtures indicated that the chitosan could only be used as a selective depressant for chalcopyrite and talc separation at pH3.