Simultaneous leaching of rare earth elements and phosphorus from a Chinese phosphate ore using H3PO4

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.

Keywords

• rare earth elements
• phosphate ore
• acid leaching
• phosphoric acid