A Highly Selective Reagent Scheme for Scheelite Flotation: Polyaspartic Acid and Pb-BHA Complexes

Previous studies have proved that the lead complexes of benzohydroxamic acid (Pb-BHA) are effective collectors of scheelite flotations; however, the separation of scheelite from calcite needs depressants with high selectivity. In this study, we reported a novel depressant for calcite minerals, and Pb-BHA served as the collector of scheelite. The flotation behavior of polyaspartic acid (PASP) in a scheelite and calcite flotation that uses Pb-BHA was determined via flotation experiments. Furthermore, the selective adsorption of PASP on the mineral surfaces and the effect of PASP on the adsorption of Pb-BHA on the mineral surfaces were investigated through zeta potential measurements, X-ray photoelectron spectroscopy (XPS), crystal chemistry calculations, and Fourier transform infrared spectroscopy (FTIR) measurements. Thus, PASP demonstrated high selectivity in both scheelite and calcite and contributed to the successful separation of scheelite from calcite. PASP exhibited a higher adsorption capacity and stronger chemisorption with the active sites of calcium atoms on the calcite surface. The crystal chemistry calculations indicated that the distance of the PASP functional groups matched with the calcium distance of a calcite mineral surface, which can be attributed to the selectivity of PASP. Furthermore, the adsorption of PASP impeded the adsorption of Pb-BHA on the calcite surfaces, whereas the opposite was the case for scheelite. The mutually reinforcing selectivity of PASP and Pb-BHA considerably contributes to the efficient flotation separation of scheelite from calcite.