The role of phosphate in inhibiting the activation of quartz flotation induced by Mg2+

As a common gangue in many mineral flotation processes, the activation of quart by inevitable cations will worsen the flotation separation of valuable minerals from quartz. In this work, phosphate was selected to inhibit the activation of quartz flotation by Mg 2+ , and the role of PO 4 3− during flotation was deeply studied by density functional theory (DFT) calculation and a series of research methods. Micro-flotation experiments demonstrated the strong activation effect of Mg 2+ on quartz at pH 10, and the activation effect was significantly inhibited upon adding PO 4 3− to the flotation solution. DFT calculation predicted that Mg hydroxyl compounds (MgOH + and Mg(OH) 2 ) were easily adsorbed onto quartz surface, while Mg 3 (PO 4 ) 2 generated from the reaction between PO 4 3− and Mg 2+ would not be adsorbed onto the quartz surface, which was supported by zeta potential measurement, X-ray photoelectron spectroscopy (XPS) detection, and, scanning electron microscopy coupled with energy dispersive spectroscopy (SEM-EDS) test. Fourier transform infrared spectroscopy (FTIR) tests indicated that the Mg hydroxyl compounds adsorbed onto quartz surface would induce the adsorption of NaOL, which was responsible for the activation of quartz flotation. The addition of PO 4 3− to flotation solution containing Mg 2+ could effectively inhibit the generation of Mg hydroxyl compounds and the subsequent adsorption of NaOL, thereby achieving the depression of quartz flotation. This work provided an effective way for the depression of quartz flotation in complicated flotation systems.