Effect of modified dextrins on the depression of talc and their selectivity in sulphide mineral flotation: Adsorption isotherms, AFM imaging and flotation studies

Three novel dextrin polymers of varying functional group chemistry but similar molecular weight have been used to depress talc in single and mixed mineral studies. The mixed mineral system was a model sulphide ore consisting of talc, pentlandite and chalcopyrite. Adsorption isotherms for the three polymers on both valuable and gangue mineral phases were determined to give initial clues as to the ability of the polymers to depress talc. Flotation testing revealed a distinct hierarchy of effectiveness of the polymers in the depression of talc in the single mineral system (MP Dextrin > CM Dextrin > Dextrin TYM) reflecting the observed adsorption affinity and adsorbed amount of the polymers on talc. Atomic force microscopy (AFM) imaging of the polymers on the basal plane of talc gave further insight to the observed single mineral flotation trends with differences observed amongst the polymers in terms of adsorbed layer thickness and coverage. A different order of effectiveness was observed for talc depression in the mixed mineral system (CM Dextrin >= MP Dextrin > Dextrin TYM). Competition between the valuable and gangue mineral phases for the uptake of MP Dextrin is responsible for its observed decrease in efficiency in mixed mineral flotation. All three polymers were found to be reasonably selective in their action although at high dosages the polymers began to affect the flotation of the valuable minerals.