An integrated strategy for the extraction and solidification of Th(IV) ions from aqueous HNO3 solution based on self-assembly triggered by [DODMA]+[DGA]- ionic liquids

Based on the dioctadecyldimethylammonium chloride surfactant, three novel ionic liquids (ILs) involving dioctadecyldimethylammonium ([DODMA](+) cations and N,N-dialkyl-diglycolamide acid (DGA) anions was firstly designed and synthesized for extraction of thorium ions in nitric acid solution. The integrated extraction and solidification of Th(IV) was developed by formation of self-assembly (SA) solid in two-phase interface. The SA solid was identified by spectroscopic methods including SEM with mapping EDS, XPS, FT-IR and ESI-HRMS. The excellent extraction efficiency was observed for extraction of thorium using [DODMA](+)[DGA](-) ionic liquids, more than 99% of Th(IV) were extracted and enriched as SA solid in one-step process. The outstanding selectivity of Th(IV) to Ln(III) and U(VI) was observed, and separation factors were up to 3470 for Th/Eu and more than of 1980 for Th/U, respectively. The proposed strategy not only provides an alternate method for the separation of thorium ions with uranyl ions and lanthanides(III) ions in the nuclear fuel cycle, but also pioneers to develop the self-assembly extraction based on [DODMA] thorn ionic liquids. In view of the similarity of Pu(IV) and Th(IV), the simple integrated strategy may be further expanded for extraction and enrichment of Pu(IV) in nuclear industry.

Automated summary

In this study, three novel ionic liquids were designed and synthesized for the extraction of thorium ions in a nitric acid solution. The thorium ions were extracted and solidified through the formation of self-assembly solid at the two-phase interface. One of the ionic liquids showed excellent extraction efficiency with over 99% thorium extraction in a one-step process, and exhibited outstanding selectivity.