A comparative investigation into floatability of bastnaesite with three di/trialkyl phosphate surfactants

Abstract

Flotation separation and recovery of rare earth minerals (REM) have returned to an important position due to the growing strategy demand for rare earth elements (REE). In this paper, a comparative investigation into the floatability of bastnaesite ((Ce,La)FCO3) was conducted by using three di/trialkyl phosphate collectors, di(2-ethylhexyl) phosphate (DEHPA), dibutyl phosphate (DBP) and tributyl phosphate (TBP). The density functional theory (DFT) computation recommends that the chemical activity of the three phosphate collectors is in order of DEHPA ≥ DBP >> TBP, and their hydrophobization as-suggested by the lgP (oil-water partition coefficient) value is in the order of DEHPA > TBP > DBP. The micro-flotation indicates that the preferable pH values for flotation of bastnaesite with the three phosphate collectors are 7.0–8.0, and DEHPA achieves much higher flotation recovery of bastnaesite, followed by DBP, and then TBP, which coincides with their reactivity and hydrophobicity, the two prerequisites for froth flotation. The contact angle, zeta potential, Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) deduce that DEHPA likely reacts with the Ce(Ⅲ) atoms of bastnaesite interface through its O atom(s) of the P(=O)–O– group to generate the Ce–O–P bonds, and its two 2-ethylhexyl groups orient outside for attaching bubbles, resulting in flotation enrichment of bastnaesite. Furthermore, this investigation offers a novel strategy for developing collectors in selective beneficiation of REM.