Phase Crystallization in the CePO4–NaF System

Abstract

The phase crystallization in the CePO₄–NaF system was studied in order to develop an industrial process for rare earth metal recovery from a phosphate salt melt formed upon liquation of the rare earth ores from the weathering crust of the Tomtor deposit. The phosphate salt melt accumulated TR₂O₃, P₂O₅, Sc₂O₃, and Y₂O₃, and the silicate melt contained Fe₂O₃ and Nb₂O₅. Chemical reactions between CePO₄ and NaF in the phosphate salt melt induced crystallization of the double phosphate Na₃Ce[PO₄]₂ and the fluoride phosphate Na₂CePO₄F₂. The products of melt crystallization in the CePO₄–NaF system incongruently decomposed in dilute mineral acids (HNO₃) to give an insoluble precipitate containing CeO₂ and CeF₃.