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The adsorption and action of various polymers on talc has been investigated. Two families of polymers (starch-based polysaccharides and synthetic polyacrylamides) with specific molecular weights and functional group chemistry were studied. Adsorption isotherms, acoustophoresis, and contact angle studies enabled polymer adsorption behaviour, adsorbed layer thickness, and the hydrophilicity of the polymer-treated talc surface to be determined. Flotation testing on the treated talc revealed a hierarchy of effectiveness within the group of polymers studied. The observed trends in flotation performance are discussed with reference to the measured polymer layer properties. A 3D correlation plot of adsorbed layer thickness and contact angle against flotation recovery indicates that it may be feasible to predict an order of effectiveness for polymeric depressants based solely on measurements of the adsorbed layer properties, without recourse to flotation testing. This approach would be desirable when screening large numbers of potential depressants.

Three polymers of varying chemistries and molecular weights have been used to depress talc in a model sulphide ore consisting of talc, pentlandite, and chalcopyrite. Flotation testing revealed a distinct hierarchy of effectiveness of the polymers in the depression of talc (HP Starch > Polymer-H > Dextrin-WY) but a different order of effectiveness for depression selectivity (Dextrin-WY > Polymer-H > HP Starch). Adsorption isotherm determinations for the gangue and valuable mineral phases indicate that the differences in selectivity are partially due to adsorbed amount variations, with Dextrin-WY adsorbing marginally less on the sulphides than Polymer-H. Contact angle measurements on packed particle beds have revealed that the polymers have differing abilities to reduce the contact angle of talc and the sulphide minerals. An explanation of the observed trends is given in terms of the binding mechanisms of the polymers on the talc and the sulphide mineral phases. Order of addition effects between collector and depressant were also investigated using adsorption isotherm determinations for the polymers (collector) in the presence of a pre-adsorbed layer of collector (polymer). Adsorption of the polymers was not affected by the presence of the collector and vice versa.

Advancing water contact angles were measured on freshly cleaved talc faces as well as on talc particles. The intrinsic hydrophobicity of talc was shown to be due to the dominance of the apolar components of the work of adhesion. Polyacrylamides and polysaccharides adsorb onto the surface of talc, displaying strikingly different morphologies. Adsorbed amount, apparent layer thickness, and polymer structure control talc wettability.

The adsorption of a polyacrylamide (MW 14600) and two polysaccharides (MW 9260 and 706 x 10(3)) onto model silica surfaces of different hydrophobicities was investigated. In all cases, adsorption adhered to the Freundlich isotherm, reflecting the heterogeneous character of the solid substrates. The latter strongly influenced the character of the adsorbed polymer, with morphologies from chainlike structures to thin films and patches being observed. Surface roughness, polymer type, and molecular weight also play roles in controlling adsorbed polymer morphology. Surface wettability is strongly influenced by the thickness of the adsorbed layer.