Improvement of Egyptian talc quality for industrial uses by flotation process and leaching

Abstract

Talc is an industrial mineral that is widely used. It is always associated with other minerals, which determine the quality of talc samples for industrial purposes. Various operating variables control the natural floatability of talc. For enhancement of talc flotation, sodium hexametphosphate is used as a depressant for associated gangue minerals. In addition, oleic acid (in an equal mixture with kerosene) is used as an anionic collector. The results presented in this paper provided useful and important information on how to improve the quality of Egyptian talc, obtained from different sites, for industrial uses. The optimum conditions were obtained at pH=11, depressant dosage=1.0 kg/t, collector dosage=1.2 kg/t and pulp density=200 g/L. At these conditions, SiO2 assay increased from 54.10% to 54.94%, MgO assay increased from 29.90% to 31.76%, CaO decreased from 0.80% to 0.42%, Al2O3 decreased from 5.50% to 3.11%, Fe2O3 decreased from 8.20% to 7.24%, the whiteness increased from 75.4% to 83.7%, and the loss on ignition decreased from 6.64% to 5.21%. The mass recovery of final concentrate was 92.4%. The component recoveries of SiO2 and MgO (the major constituents of talc) in the final concentrate were 93.8% and 98.2%, respectively. More improvement of talc quality was obtained by leaching the final concentrate of flotation with a 10% diluted hydrochloric acid. The mass recovery of final product was about 85% of initial feed. In this final product, Fe2O3 decreased to 3.12%, CaO decreased to 0.38%, and Al2O3 decreased to 3.01%. The assay of SiO2 increased to 58.96%, MgO percent was nearly the same as in the final concentrate of flotation, the whiteness increased to 88.5%, and the loss on ignition decreased to 4.03%. The final product may be suitable for many industrial uses such as low-loss electronics (a type of ceramics), paints, rubber, plastics, roofing, textiles, refractories, insecticides and coating of welding rods.