Dissolution behaviors of rare earth elements in phosphoric acid solutions
(1. National Engineering Research Center for Rare Earth Materials, GRINM Group Co., Ltd., Beijing 100088, China;
2. School of Metallurgical and Ecological Engineering, University of Science and Technology Beijing, Beijing 100083, China)
2. School of Metallurgical and Ecological Engineering, University of Science and Technology Beijing, Beijing 100083, China)
Abstract: In order to provide practical fundamental data for rare-earth elements (REEs) recovery from phosphoric acid and to better understand REEs behavior during the phosphoric acid evaporation process, the solubilities of REEs in phosphoric acid with various concentrations of phosphorus at different temperatures were measured. A simple linear model between REEs solubility and phosphoric acid concentration is built and the experimental data are found to fit it very well (R2>0.94). Hydrogen-ion concentration is found to be the predominant factor controlling the solubility of REEs in phosphoric acid. In addition, the solubility of REEs in phosphoric acid is found to sharply decrease with increasing temperature, which can be attributed to the increase of the Gibbs energy of the REEPO4 dissolution reaction or the restraint of the disassociation of phosphoric acid molecules owing to the elevated temperature.
Key words: rare earth elements; phosphoric acid; dissolution behavior; rare earth phosphates; temperature