The separation of thorium and rare earth elements using [A336][NO3]: insight into a new extraction mechanism

In this study, extraction and separation of thorium(IV) and a few representative rare earths in HNO3 media was evaluated using trioctylmethylammonium nitrate ([A336][NO3]) ionic liquid. An unexpected novel extraction mechanism was identified based on the studies in the slope analysis and ESI–MS spectrum. The trimer of [A336][NO3] was confirmed to dominate the extraction reaction by ESI–MS spectrum before and after the extraction. The extraction efficiency of La(III), Eu(III) and Lu(III) by [A336][NO3] are much lower than Th(IV) in acid medium, which means that it is possible to separate thorium from rare earths or the rare earth ores by using [A336][NO3].