APPLICATION OF A336P507/P204 ON HIGH SELECTIVE EXTRACTION AND SEPARATION OF RARE EARTHS(III) FROM MECHANISM TO TECHNIQUES

摘要

To address the concerns about the low utilization of rare earth resources and environmental pollutions, especially the tailings containing radioactive thorium in China, we invented a type of new ionic liquid extractants (ILE), such as [trialkylmethylammonium] [di-(2-ethylhexyl)orthophosphinate] ([A336][P507]) and [trialkylmethylammonium] [di-2-ethylhexylphosphinate] ([A336][P204]). A systematic investigation of ILEs on RE extraction was conducted. The effects of aqueous equilibrium pH, different acid medium (HNO_3, HCl, H_2SO_4 ), extractant concentration, salting-out agent concentration, and stripping property were investigated. According to separation factors (β), [A336][P507] and [A336][P204] were suitable for the separation of heavy REs(III) in nitrate medium and the separation of light REs(III) in chloride medium. In nitrate medium the β values were Tm/Er (3.36), Yb/Tm (7.92) and Lu/Yb (8.55), respectively, when [A336][P204] was used as extractant. In chloride medium the β were Nd/Pr (9.52) and Sm/Nd (4.70), respectively, when [A336][P507] was used as extractant. The extraction mechanism for the high selectivity of RE(III) was discussed. Further improvement and potential application of [A336][P507] in RE(III) separation was recommended. Based on the separation results of ILE on RE extraction, a two-step decomposition of Bayan Obo RE concentrate process was developed to reduce the radioactive thorium waste residue and improve the utilization of RE, thorium, F and P values. A new separation technique of heavy RE from ion-absorbed RE deposits was also developed to meet the demand for heavy RE in laser crystals.