Pyrometallurgical Treatment of Apatite Concentrate with the Objective of Rare Earth Element Extraction: Part I

Abstract

Apatite, Ca5(PO4)3F, concentrate from LKAB in Kiruna, Sweden, has been characterized and pyrometallurgically treated using (i) silicon metal and fluxes to extract phosphorus and transition metals at 1600 °C (Part I publication), and (ii) carbon to extract phosphorus without fluxing at temperatures exceeding 1800 °C (Part II publication), with the ultimate objective to recover rare earth elements from the resulting slag/residue phases. A variety of methods (SEM/EDS, EPMA, DTA-TGA, Sessile drop, ICP-MS/OES, and XRD) have been used for the characterization and analysis of both the concentrate and reaction products. Elemental deportment, except for the rare earth metals, is broadly in line with the equilibrium thermodynamic predictions performed using HSC Chemistry®. Phase diagrams were predicted using FactSage® and a custom phosphate database to explain the observed melting/fluxing behaviors.