Phosphate rock has been considered as one of the most significant secondary rare-earth resource, and the utilization of rare earth elements (REEs) in phosphate rock has attracted increasing attention. In this study, the leaching kinetics of REEs from a phosphate ore from China was studied with the variation of temperature and phosphoric acid concentration under the conditions: ratio of liquid to solid of 12 mL/g, stirring speed of 120 r/min, and phosphate particle size of −0.074 mm amounts 61.1%. The results suggest that there were two distinct stages in leaching process and kinetics of both stages followed shrinking core model. At fast reaction stage, the semi-empirical equation describing the kinetics was 1 − 3(1 − α)2/3 + 2(1 − α) = 1.885CH3PO40.89exp(−11220/8.31T)t. The semi-empirical equation for slow reaction stage was 1 − 3(1 − α)2/3 + 2(1 − α) = 0.299CH3PO42.50exp(−18720/8.31T)t. Using shrinking core model and time-to-a-given-fraction method, we found that leaching rate of fast reaction stage was controlled by solid product layer diffusion, and both solid product layer diffusion and chemical reaction determined slow reaction stage.

No abstract

Although phosphate rock has been considered as a potential new rare earth elements (REEs) resource, the recovery of REEs from phosphate rock is impeded by technical challenges and cost issues. This study investigated the effects of operation conditions on the leaching efficiencies of REEs and phosphorus from Zhijin phosphate ore, a large phosphate deposit in China. The leaching process overtime was also studied by chemical analysis, scanning electron microscope with energy dispersive spectroscopy (SEM-EDS), and X-ray diffraction (XRD). The results indicated that the REEs from Zhijin phosphate ore were mainly present in fluorapatite and dolomite, and REEs had similar trends of leaching efficiency to those of phosphorus and magnesium. Under the conditions of 25 wt% phosphoric acid concentration in the initial pulp, a weight ratio of liquid to solid of 12 mL/g, a temperature of 60°C, an agitation speed of 220 rpm, and leaching time of 120 min, REEs and phosphorus leaching efficiencies of 97.8% and 99.7% were obtained. Most parts of dissoluble substances were decomposed within 30 min. Chemical analysis, SEM-EDS, and XRD results indicated that leaching efficiencies of minerals in Zhijin phosphate ore increased following the order: quartz, aluminosilicate, pyrite, fluorapatite, dolomite, and calcite.

No abstract

No abstract