وحید آقایی لشگری

Rare earth elements (REEs) have found many applications in various industries and technologies. Therefore, their separation from secondary resources, in addition to primary ones, has become significant. Apatite mineral is a necessary ingredient for the wet process, a chemical reaction between apatite and sulfuric acid that culminates production of phosphoric acid. In addition, a by-product called phosphogypsum (PG) is obtained, which is an important secondary source for REEs. In this research with the focus on cerium, lanthanum, neodymium and yttrium, the wet process and the factors affecting it such as temperature and solid to liquid ratio (S/L) were investigated. It was found that temperature has no significant effect on the recovery of REEs and increasing S/L ratio increases REE deposition in PG. Then, the optimum conditions for depositing maximum amount of REEs in PG were determined. After that, a large amount of PG was generated under optimum conditions and its properties were investigated. Then, the PG leaching process was performed by nitric acid solution. The effects of temperature, S/L ratio and acid concentration were evaluated. It was found that the leaching efficiency increases with increasing temperature, decreasing S/L ratio and increasing nitric acid concentration. Finally, the optimum conditions of the aforementioned step were determined for the maximum separation of REEs.