Effect of Rare Earth Dissolution on Rare Earth Elements by Solvent Extraction from Malaysian Rare Earth Oxalate

¹ Mineral Processing Technology Division, Mineral Research Centre, Department of Mineral and Geoscience Malaysia, Jalan Sultan Azlan Shah, 31400 Ipoh, Perak, Malaysia.
² MINPRO Sdn. Bhd. No. 318, Jalan Jelutong, Kg. Dato Ahmad Said Tambahan 3, 30020 Ipoh, Perak, Malaysia.
³ Faculty of Applied Sciences, Universiti Teknologi MARA, 02600 Arau, Perlis, Malaysia.

^* Corresponding author: tinesha@jmg.gov.my

Abstract

Light rare earth elements (LREEs), including Lanthanum (La), Cerium (Ce), Praseodymium (Pr), Neodymium (Nd), and Samarium (Sm), are crucial for modern technologies. Notably, Nd and Pr are core components in permanent magnets for high-efficiency electric motors and generators, essential for low-carbon technologies, and their demand is projected to rise significantly. This study successfully characterized a rare earth oxalate (REOx) sample from undisclosed location in Malaysia, and optimized key conditions for its REE extraction. Initial characterization using X-ray fluorescence (XRF) showed the REOx contained 90.02 wt.% total rare earth elements (TREE), with 9.98 wt.% impurities. Inductively Coupled Plasma Mass Spectrometry (ICP-MS) further quantified the TREE in the REOx at 9656.50 mg/L. The study began by optimizing the dissolution process of REOx using hydrochloric acid (HCl). Parameters investigated included the liquid-to-solid ratio (L/S) (2:1 to 10:1, with 1.0 M HCl for 10 minutes) and HCl concentration (0.2 M to 1.8 M). The optimal dissolution was achieved at an L/S of 10:1, yielding 92.02% TREE extraction, and an optimal HCl concentration of 0.2 M, resulting in 86.98% TREE separation. These optimized conditions facilitated efficient REE extraction while minimizing acid usage. Following dissolution optimization, a 10-stage scrubbing process was conducted using 1.0 M HCl at each stage. The initial impurity concentration (Fe, K, Mg, Mn, Na) after dissolution was 131.98 mg/L, of which 94.50% were successfully removed after the 10^th stage. During scrubbing, LREE recovery into the organic phase progressively increased across the stages, achieving over 97% overall recovery. Specifically, La and Ce recoveries reached 100% (from initial 99.84% and 99.83% respectively) by the 5^th stage, while Pr and Nd achieved near-complete recovery at the 6^th stage (99.97% and 99.99% respectively). These findings confirm the high effectiveness of multi-stage scrubbing for purifying LREEs from REOx.