Purification and enrichment of rare earth in ion-adsorbed rare earth ores using fatty acid based separation processes

Among many impurity elements in ion-adsorption rare earth (RE) ores, aluminum (Al) with similar structure to rare earth elements (REEs) is difficult to be removed. In this paper, four fatty acid based ionic liquids (ILs) were designed and synthesized for the purpose of removing Al impurity. Due to the better extraction and separation capacity, [methyltrioctylammonium][neodecanoate] ([N1888][NDA]) was screened and further studied. The extraction and separation conditions of Al with [N1888][NDA] were optimized, and the separation factor of Al/REEs reached 304.43. At the same time, the stripping and recycling experiment of [N1888][NDA] were carried out. [N1888][NDA] had high separation efficiency for Al and RE, which was of guiding significance for the removal of impurity. Based on the above investigations, a process combining fractional extraction and extraction-precipitation was developed to remove most of the impurity ions in the MgSO4 leaching solution. The process converted the low concentration RE sulfate solution ([RE3+] = 0.18 g·L−1) into high concentration RE chloride product ([RE3+] = 158.3 g·L−1, REO = 193.7 g·L−1). Moreover, the process effectively removed the Al, Mg and Ca in the leaching solution and the purity of RE product reached 99.2 wt%.