Selective flotation separation of apatite from calcite using hydrolytic polymaleic anhydride as an eco-friendly and efficient depressant

Abstract

Flotation separation of apatite from calcite has always been challenging because of the similar surface physicochemical properties of apatite and calcite. In this study, hydrolytic polymaleic anhydride (HPMA) was used as an eco-friendly and efficient inhibitor to enhance the flotation separation efficiency of apatite from calcite. The depression performance of HPMA on these minerals was explored using microflotation experiments and bench-scale flotation tests. The adsorption behavior and inhibiting mechanism of HPMA were investigated using zeta potential analysis, surface wettability analysis, adsorption amount measurements, and X-ray photoelectron spectroscopy. Microflotation experiments revealed that HPMA presented selectively inhibitory action on calcite flotation and negligible effect on apatite flotation. The bench-scale flotation experiments demonstrated that effective flotation separation of apatite from calcite can be achieved using HPMA as the depressant and sodium oleate (NaOl) as the collector. Under these experimental conditions, an apatite concentrate with P2O5 grade of 36.21 ± 0.71% and recovery of 81.18 ± 1.84% was obtained. Mechanism investigation indicated that HPMA was strongly adsorbed on the calcite surface via chemical reactions between the carboxyl groups of HPMA and activated Ca sites of calcite. This significantly hindered subsequent NaOl adsorption. By contrast, the amount of HPMA physisorbed on the apatite surface was significantly smaller, and its effect on the subsequent adsorption of NaOl on the apatite surface was limited. Accordingly, the selective depression of calcite flotation and efficient flotation separation of apatite from calcite were achieved. In summary, HPMA can be used as a potentially green and highly efficient inhibitor in the flotation separation of apatite from calcite.