Decomposition of monazite in Bayan Obo rare earth ore by roasting of Na2CO3 pellets

Abstract

To resolve the issue of rotary kiln agglomeration during the sodium carbonate roasting of dolomite rare earth ore, this study introduces an oxidation-sodization pellet roasting method for decomposing mixed rare earth concentrates. The focus of this paper lies in understanding the bonding and roasting mechanism of sodium polyacrylate as a binder to dolomite ore and examining the process index of Na2CO3 pellets roasting-acid leaching using X-ray diffraction (XRD), scanning electron microscopy with energy dispersive spectroscopy (SEM-EDS), and zeta potential analysis. The results indicate that sodium polyacrylate facilitates the bonding of sodium carbonate to monazite via adsorption of positive and negative charges, and upon roasting at 750 °C for 1.5 h to obtain rare earth oxides. Under conditions of a hydrochloric acid (HCl) concentration of 9 mol/L, a reaction for 60 min, a solid-to-liquid ratio (g:mL) of 1:5, and reaction temperature of 90 °C, the leaching rates of rare earth elements and thorium (Th) reached maxima of 85.14% and 95.53%, respectively. The process results in a yield of 47.61% for fluorine (F) and 89.25% for phosphorus (P). This research forms a foundation for the sodium carbonate roasting decomposition of mixed rare earth concentrates.