Recovery of light rare earth elements, cerium, lanthanum, and neodymium from alluvial gold mining waste from the Bagre-Nechi mining district in Colombia using acid leaching, oxalate precipitation and calcination

This paper investigates different leaching conditions with hydrochloric acid and sulfuric acid, which perform the maximum extraction of cerium, lanthanum, and neodymium from a dephosphorized monazite concentrate ob-tained from alluvial gold mining waste from the Bagre-Nechi mining district in Colombia, for the subsequent recovery of oxides of these metals. Sulfuric acid as the leaching medium at all evaluated concentration, time, and temperature conditions gave highest extractions. The addition of 10% (v/v) H2O2 increased rare earth dissolution up to 93% in H2SO4 medium. Thermodynamic analysis indicates that H2SO4 solutions show a higher capacity to solubilize REEs as opposed to HCl solutions, thus supporting the experimental results. Rare earths in sulfuric acid liquor can be recovered up to similar to 100% by precipitation with a 1.0 M oxalic acid solution at 25 degrees C for 120 min, followed by the calcination of the oxalate precipitate at 850 degrees C for 120 min. The final product was characterized by XRD, which indicated a composition of CeO2, La2O3, and Nd2O3. The results of the XRD analysis show the REE phase transformation throughout the process.