An Efficient Selective Depressant for the Flotation Separation of Scheelite from Calcite Based on Experimental and Calculational Studies

Scheelite and calcite minerals contain similar calcium-active sites, leading to a mutual transformation upon dissolution of surface components. At the same time, the traditional oxide ore collector lacks selectivity, and it is difficult to separate the two minerals by flotation. This study investigated the selective adsorption mechanism of tetrasodium iminodisuccinate (TI) during the flotation separation of scheelite and calcite. The flotation behavior of both minerals was analyzed through single-mineral and artificially mixed-mineral experiments. The results revealed that with the addition of a TI concentration of 5 × 10^–4 mol/L as a depressant, scheelite and calcite exhibited recoveries of 88.69% and 13.81%, respectively. This indicates that TI selectively depressed calcite and achieved an effective flotation separation. TI undergoes dissolution in the slurry solution, generating anions and sodium ions. The anion groups are adsorbed on the mineral surface, negatively changing the zeta potential of the mineral surface. This was likely due to a coordination reaction between the carboxylate ions of TI and the Ca sites on the calcite surface, forming the COO–Ca species. Moreover, TI adsorption increased the signal intensity of the characteristic ion COOH^– on the calcite surface, forming a dense adsorption layer with clustered peaks. TI molecules adsorbed onto the calcite (104) surface, creating a hydrophilic film that significantly reduced the surface hydrophobicity. This study effectively realizes the flotation separation of scheelite and calcium-containing minerals, and the research and development of an environmentally friendly organic depressant is the focus of future research.