Investigations into the extraction of rare earth elements from Zandkopsdrift ore using the sulfation roasting process

Abstract

Sulfation roasting test work was conducted to investigate the selective extraction of rare earth elements (REEs) from the REE-bearing Zandkopsdrift (ZKD) ore from the Southern Africa region. Sulfation roasting efficiency and selectivity were studied through the determination of phase compositions and leaching efficiencies of REEs from roasted materials. The results showed that REE extraction efficiencies increased with temperature, time and oxygen (O2) content in the reaction gas. The highest LREE extractions, 88 % La, 87 % Pr, 86 % Nd, and 61 % Ce, were obtained for tests conducted at 700 °C for 8 h in an O2-enriched SO2-O2 gas atmosphere. Fe was the least extracted metal at all the roasting conditions investigated, therefore indicating successful selectivity of the LREEs using the sulfation roasting process. Mineralogical analysis of the roast products showed decomposition of the REE-bearing phosphate phases, i.e. monazite and florencite, while Fe was contained in the hematite phase and thus indicating minimal sulfation. Gas-based sulfation and leaching was found to be technically feasible for the selective extraction of Light REEs (LREEs) from the REE-bearing ZKD ore from Southern Africa.