In-line extraction of REE from Dihydrate (DH) and HemiDihydrate (HDH) wet processes

Abstract

Phosphate rock (PR) contains traces of rare earth elements (REEs), ranging from 100 to 1000μg/g. However, REE may be regarded as s secondary source for REE since large tonnages of PR are mined annually and used in phosphoric acid production.In this work, batch leaching tests were conducted to simulate (DH) and (HDH) wet processes in order to determine REE distribution in the product acid and phosphogypsum (PG). Then REE was extracted in-line during PR acidulation using Tributyl Phosphate (TBP) diluted with kerosene and ion exchange resin DOWEX- 50WX8 (−300+150μm).It was found that in DH process, approximately 80% of the feed REE reported to PG; about 65% of them were LREE while HREE constitute 64% of REE reported to the product acid. On the other hand, REE reported to PG in HDH process was slightly higher than DH; approximately 84% of the REE was reported to PG; 62% of them were LREE while 70% of REE reported to product acid was HREE.It was also found that REE was efficiently extracted by ion exchange resin than TBP solvent: REE in PG was increased by 230%, from 335.3 to 1106.6μg/g, with ion exchange resin compared to 45% REE reduction (from 335.3 to 182.27μg/g) when TBP solvent was added. The main challenge is to efficiently separate the loaded resin beads from the fine grained PG and acid insoluble residuals.