Elucidação da ação do silicato de sódio como depressor na flotação de calcita e quartzo

Abstract

This work aimed to elucidate the sodium silicate action mechanism as a depressor in the flotation of the minerals quartz and calcite. The experiments were done with high-purity mineral samples (quartz and calcite) in the particle size range below 147μm. The samples were characterized in size distribution (diffraction laser), chemical composition (X-ray fluorescence) and mineralogical composition (X-ray diffraction). The study of flotation in Hallimond tube showed that, in all systems tested, the efficiency of sodium silicate increased with the concentration. At concentrations above 1.500g/t, it was obtained almost total depression (96% for calcite and 97% for quartz). The most efficient depression pH range was observed between 5 and 8. Starting from 11 pH, the sodium silicate did not work as a depressor. The infrared spectra obtained at 7 pH, after contact of sodium silicate, showed the presence of the groups OH and Si-OH, both suggesting that the adsorption of the species Si(OH)4, as well as siloxane groups (Si-O-Si) attributed the adsorption of polymeric species.