Multistage leaching of rare earth elements from primary source: a sustainable approach to avoid fluorine contamination by roasting with aluminum hydroxide: Lixiviation en plusieurs étapes des éléments de terres rares à partir d’une source primaire: une approche durable pour éviter la contamination par le fluor par grillage avec de l’hydroxyde d’aluminium

Bastnaesite ore (primary source), with a formula of REE (CO₃) F, contains light rare earth type of cerium (Ce) and lanthanum (La) rich content along with 8–10% fluorine. A conventional method such as direct acid leaching causes environmental apprehensions such as the evolution of HF gas which causes adverse effects on the environment. Therefore, a novel and sustainable beneficiationmetallurgy process comprised of roasting the ore with the aluminum hydroxide (Al (OH)₃) to deactivate fluorine followed by hydrochloric acid leaching and multistage water leaching was proposed. Leaching from roasted ore was achieved with hydrochloric acid and several parameters affecting REE were optimized. The best results were achieved at a pulp density of 10% w/v, the temperature of 45 °C, 4 mol/L of HCl dosage, 6% of hydrogen peroxide, time of 240 min, and agitation of 280 rpm. Consequently, percentage extraction of Ce and La reached 97.80 and 95.07 % respectively with a high purity of REE oxide product at optimum conditions. Multistage leaching was established at optimum conditions and the percentage recovery of REE was found to be ≥ 99.24%. XRD and SEM-EDX analyses confirmed the formation of metal fluoride complexes (MFx) and recovery of REE.