Abstract
In this study, the separation of lanthanides from phosphate ore using oxalic acid (C2H2O4), tartaric acid (C4H6O6), lactic acid (C3H6O3), sulfuric acid (H2SO4) and hydrochloric acid (HCl) was investigated. The ore was characterized before and after leaching processes by X-ray fluorescence (XRF), Scanning electron microscope (SEM), X-ray powder diffraction (XRD), and Fourier transform infrared (FTIR). The different parameters affect the leaching rate such as leaching time, acid concentration, liquid/solid ratios, temperature, and leaching kinetics were studied. The optimal leaching conditions were determined as 0.4M C2H2O4, 2.5M C4H6O6, 1.8M C3H6O3, 2.0M H2SO4, and 3.0M HCl, with a liquid/solid (L/S) mass ratio of 6/1 C2H2O4, 8/1 for both C4H6O6 and C3H6O3, 5/1 for both H2SO4 and HCl at 30°C, agitation rate ≈ 350rpm and particle size ≈ 144.8μm. Under these optimum conditions, the recovery percentage (%R) was 42.8% (for C2H2O4), 93.2% (for C4H6O6), 89.1% (for C3H6O3), 89.3% (for H2SO4), and 74.6% (for HCl). SEM and FTIR characterizations for the residue were investigated. Experimental data reveal that the leaching processes are fitted by chemical reaction models for C2H2O4 and C3H6O3, and by diffusion-reaction model for C4H6O6, H2SO4, and HCl. The activation energies for these models were estimated to be 43.3, 30.33, 45.8, 31.3, and 38.6kJ/mol for C2H2O4, C4H6O6, C3H6O3, H2SO4, and HCl, respectively. All data were confirmed and explained by XRD, FTIR, and SEM studies.