In situ separation and characterization of britholite crystals in RE‐bearing slag via supergravity.

Bayan Obo ore has abundant rare earth (RE) reserves, and RE elements (REEs) are mainly transferred into the RE‐bearing slag. However, the utilization of RE‐bearing slag is greatly limited due to the serious lack and ambiguity of RE crystals. In this study, in situ separation of RE crystals from RE‐bearing slag via supergravity was developed, and the high‐purity crystals of britholite with various REEs contents were selectively separated from the CaO–SiO2–CaF2–P2O5–Ce2O3 system with a high REEs recovery ratio of 95.58%–98.65%. On this basis, the chemical formula, the crystal structure, and the formation mechanism of britholite were characterized from the high‐purity crystals through a combination of the Rietveld refinement and DFT calculation. It was found that the britholite was verified to be evolved from Ca5(PO4)3F, there would be an SiO44− instead of a PO43− when a Ce3+ replaced a Ca2+, the chemical formula changed from Ca5(PO4)3F to Ca4.377Ce0.623Si0.6P2.4O12F, Ca3.956Ce1.044Si1.01P1.99O12F, and Ca3.176Ce1.824Si1.93P1.07O12F with the increase of REEs content, and the substitution range of REEs was between 0 and 2. This study supplements some necessary basic data of RE crystals, which provides the theoretical reference for efficient recovery of RE resources and sustainable utilization of RE‐bearing slag. [ABSTRACT FROM AUTHOR]