Flotation separation of bastnaesite from fluorite with an eco-friendly depressant polyepoxysuccinic acid and its depression mechanism

In this work, an eco-friendly depressant polyepoxysuccinic acid (PESA) was introduced for the flotation separation of bastnaesite from fluorite using octyl hydroxamic acid (OHA) as the collector. The depression effect and mechanism of PESA on the fluorite and bastnaesite were investigated by micro-flotation tests, contact angle, adsorption experiments, Fourier transform infrared spectroscopy (FT-IR), and X-ray photoelectron spectroscopy (XPS). The flotation results showed that the recovery of fluorite decreased by 89.71% when 4 mg/L PESA was added to the flotation system, while the bastnaesite recovery only exhibited a slight reduction of 2.88% under these conditions. Wettability results suggested that the PESA in the presence of OHA could make the fluorite surface hydrophilic, whereas it had a negligible impact on the hydrophobicity of the bastnaesite surface. The addition of PESA could impede the OHA adsorption on fluorite surface, which was revealed by adsorption tests and FT-IR, and the XPS analysis confirmed that the chemisorption of PESA on the Ca sites of fluorite occurred. For bastnaesite, the adsorption of OHA still could be detected, making the bastnaesite well floatable. Therefore, the efficient separation of bastnaesite from fluorite could be achieved with the PESA as a selective depressant.