Feasibility studies on Talc beneficiation by flotation

Abstract

Talcs unique properties make it an important ingredient for making ceramics, paint, paper, roofing material, plastics, rubber, insecticides, cosmetics and many other products. A talc sample from Karnataka state, India consisting of quartz and calcite as gangue and analyzing 43.99% SiO2, 23.36% MgO and 15.50% CaO was attempted for its quality improvement by flotation. Effect of process parameters such as mesh-of-grind, different types of depressants, collectors, combination of collectors, frothers and pH on the separation of talc from calcite was studied. The MgO content in talc could be improved to 28.09% and CaO was decreased to 10.42% using sodium hexa meta phosphate (2.0 kg/t) as dispersant and MIBC (0.159 kg/t) as frother with 75.51% recovery of MgO. Introduction of oleic acid, tertiary amine, a combination of oleic acid and diesel and octyl hydroxamate as collectors for talc, starch as depressant for calcite did not result in further reduction of CaO in the talc concentrate during flotation. Dissolution of calcite in talc by dilute HCl (inorganic acid) and acetic acid (organic acid) proved to be very effective in improving the talc quality. Talc concentrate assaying 30.38% MgO and 60.27% SiO2 could be achieved by using dil. HCl. The brightness of talc was slightly affected due to the dissolution of iron present in talc. However, by using acetic acid, the brightness of talc was improved along with the chemical assay which could be attributed to the selective dissolution of calcite and buffering effect of acetate.