1-Hydroxydodecylidene-1,1-diphosphonic acid flotation of bastnäsite: Performance and mechanism

To separate and enrich rare-earth elements (REE) minerals from their ores through flotation process has become an attracting topic for REE’s strategic position. In the present investigation, the floatability of bastnasite [(Ce,La)CO3F] was explored by using 1-hydroxydodecylidene-1,1-diphosphonic acid (HDDPA) as a collector. The micro-flotation results showed that bastnasite displayed an eminent floatability under pH 7.0–10.0, and HDDPA realized an efficient separation of bastnasite from calcite at pH around 8.0. Zeta potential and solution chemistry inferred that at pH 7.5–9.3, HDDPA3− anions were glad to replace the CO32- ions of Ce(Ⅲ) carbonates in/on bastnasite interface, resulting in a high flotation recovery of bastnasite. With increasing OH- concentration, the competition ability of OH- against HDDPA anion intensified, gradually the surface Ce(III) hydroxide species increased, and the floatability of bastnasite reduced. Fourier transform infrared (FTIR) and X-ray photoelectron spectroscopy (XPS) recommended that the surface Ce(III) of bastnasite interacted with the O atoms of HDDPA’s O P(O)O group to generate a four membered ring configuration, which hydrophobized bastnasite particles.