Leaching of rare earth elements from Malaysian monazite: effect of dephosphorization

Abstract Phosphates interfere the leaching process and raise environmental concerns when it comes to the extraction of rare earth elements (REEs) from monazite. This study investigates the dephosphorization behaviour of Malaysian monazite through a statistical design of experiments approach, focusing on the variables of baking reagents, roasting time, and temperature. The raw monazite sample was characterized using X-ray fluorescence (XRF) and X-ray diffraction (XRD) analyses, revealing the presence of phosphorus (P), rare earth elements (REEs) including cerium (Ce) and lanthanum (La), thorium (Th), and trace elements such as sodium (Na), iron (Fe), silicon (Si), and magnesium (Mg). The XRD analysis confirmed the dominance of CePO4 and LaPO4 phases in the monazite sample. The dephosphorization process was optimized, with the highest rare earth elements recovery achieved at 250°C for 4 hours using potassium hydroxide (KOH) as the baking reagent. In addition, the sample with the lowest concentration of phosphorus leached 84.1% of the rare earth elements. It indicates that a high level of phosphorus removal can lead to a significant recovery of rare earth elements (REEs) and provides significant information for environmentally friendly REE extraction practices.