Optimizing the recovery of rare earth elements from acid mine water: A sustainable approach using selective precipitation

This study focuses on the recovery of rare earth elements (REEs) from acid mine water (AMW) through a two-step selective process, which consists of a selective extraction with ion exchange followed by a precipitation stage using oxalic acid. Optimization of the effective REE recovery from sulphuric ion-exchange concentrates results in sustainable AMW management, providing a secondary resource for critical metals towards green transition. Experimental results indicate that (1) the use of oxalic acid facilitates the formation of REE-oxalate crystals, yielding recovery efficiencies in light rare earth elements (LREEs) much higher than for heavy rare earth elements (HREEs) at specific excess doses, and that (2) LREEs act as precursors for HREE precipitation. Moreover, REE-oxalate crystallization depends on the oxalic acid dose, pH, and precipitation time (PT). The longer the PT, the larger the crystals, which are economically advantageous. The study highlights that AMW is a potential secondary source for the REE recovery, which contributes to sustainable mining practices and provides confidence for further optimization of REE recovery processes. • Oxalic acid used for selective REE precipitation from AMW. • Study supports sustainable practices in REE recovery. • Experimental results indicate a potential industrial-scale REE recovery. • Optimal REE recovery: 300 rpm stirring, 0.15–0.275 M H 2 SO 4 for high rates and selectivity. • LREEs precipitated more efficiently than HREEs under specific conditions.