Interactions of tert dodecyl mercaptan with sphalerite and effects on its flotation behavior

Abstract In the flotation of sphalerite, the concomitant flotation of sulfidic (pyrite) and nonsulfidic gangue (silica) minerals significantly reduces the grade of the float concentrate. Laboratory scale experiments have been conducted to investigate the effect of tert dodecyl mercaptan (TDM) as a collector on the flotation of sphalerite. The addition of only 160 g/t copper sulfate, which is ⿼30% of that which is being used currently in the xanthate reagent scheme, improves the grade and the recovery. The selectivity for sphalerite, with respect to pyrite, has been improved significantly when copper sulfate is added with lime as the depressant, and the results could be achieved at pH 9⿿10.5. Based on the results obtained, the interaction of tert dodecyl mercaptan with sphalerite has been investigated by adsorption measurement, fourier transform infrared (FTIR) and density functional theory (DFT). It is showed that, TDM adsorbed on sphalerite surface chemically with some characteristic peaks appeared and migrated on sphalerite surface in FTIR tests. Compared with butyl xanthate, a stronger interaction between TDM and sphalerite is determined by analyses of frontier orbital energy calculation. It is also indicated that, by adsorption energy calculation, a strong interaction between TDM and ZnS (110) surface occurs, with the energy ⿿394.78 kJ/mol. The S 3p orbital on TDM interacted strongly with Zn 3d orbital on ZnS (110) surface, and electrons transferred from the Zn atom to the O atom, which resulted in a positive coordinate bond formed.