Application of Electrodialysis to Production of High-Purity Perrhenic Acid

Laboratory tests were conducted for the production of high-purity perrhenic acid using a membrane technique—electrodialysis. Four solutions were used in the tests: diluate, concentrate, anolyte, and catholyte. The experiments were carried out in a two-stream system. The influence of basic process parameters, including the flow rate of process streams or current density, on the purity of the obtained perrhenic acid were examined. Electrodialysis was also carried out as part of this research, aiming to concentrate the perrhenic acid >100 g/dm3. The concentrate solution obtained in the concentration tests, with a concentration of 148.7 g/dm3 HReO4 and 530 mg/dm3 NH4+, was then sent to the purification process using the electrodialysis method. The purification process was carried out until the concentration of NH4+ ions was <100 mg/dm3 in the concentrate. Finally, perrhenic acid was obtained with the following composition: 169.7 g/dm3 HReO4 and 70 mg/dm3 NH4+. Based on this research, a technological scheme for producing high-purity HReO4 by electrodialysis was developed.