The effect of chemical composition and molecular weight of polysaccharide depressants on the notation of talc

Polysaccharide reagents are frequently used in the mineral processing indus try to improve the grade of the concentrate by depressing the naturally flo atable gangue. A microflotation study showed that at an ionic strength of 1 0(-3) M KNO3, the dosage, molecular weight, and chemical composition of pol ysaccharide depressants affect their depressing action on talc. Viscosity r eadings for four carboxymethylcellulose (CMC) reagents and three modified g uar gum reagents are reported, and estimates of the molecular weight of the CMCs are calculated. The natural floatability of talc was diminished when guar-based polymers were added to the system. Moreover, the depression of t alc was increased as the guar molecular weight was increased. Strong depres sion of talc was achieved at a relatively low guar dosage; higher dosages d id not further increase this depression. At 10(-3) M KNO3, the CMCs were in effective depressants of talc. No systematic change in talc depression for differing molecular weight CMCs was observed. A small increase in depressio n was observed when the concentration of CMC was increased. A mechanism is proposed for the polymer-talc interactions based on these preliminary studi es and information from similar studies in literature. (C) 2000 Published b y Elsevier Science B.V. All rights reserved.