Stepwise recovery of cerium and fluorine from bastnaesite: Utilizing complex properties of B-F to obtain high purity CeO2 and KBF4

•A process for recovery of Ce and B F from bastnaesite leaching liquor has been developed.•Ce-B-F was co-extracted by Cyanex923 and stepwise separated, avoiding the precipitation of rare earth fluoride.•The complex properties under different conditions of Ce-B-F system were characterized.•The yields of B and F were 96.83 and 96.23 %.•F and Ce were recovered as KBF4 and CeO2, with a high purity of 96.92 % and 99.95 %. This research investigates a new approach for recovering fluorine and cerium from a boric-acid-added bastnaesite sulfuric leaching liquor by Cyannex923. Systematic research of the effects of H3BO3 on bastnaesite leaching, extraction and stripping process was studied. The process mechanism and conditions in each step, including concentrations, proper pH, K/B and B/F ratio and temperature, were also determined. The result describes that that the formation of B-F complex improves the extraction of Ce and F. The formation of B-F complex also provides a new method to realize the separation and stepwise recovery of Ce and F. After Ce, B and F were co-extracted, Ce/B-F loaded organic phase are stepwise stripped by H2SO4 + H2O2 and NH3·H2O, allowing recovery of KBF4 with 97.12 % purity and CeO2 with 99.95 % purity from stripping solutions. The size distribution and SEM images of KBF4 product were given as well, which showed KBF4 was mainly 1 μm particles and dispersed well. Furthermore, the whole process based on the mechanism was designed and confirmed by cascade extraction test.