A novel one-step strategy for extraction and solidification of Th(IV) based on self-assembly driven by malonamide-based [DC18DMA]+ ionic liquids

Abstract

Three novel [DC18DMA]+ ionic liquids (ILs) with N,N-dialkyl-malonamic acid (MA) anions was synthesized, which was applied for extraction of thorium ions in nitric acid solution. The solid samples were obtained by simultaneous extraction and solidification of Th(IV) based on self-assembly process. The dioctadecyldimethylammonium ([DC18DMA]+) was pioneered as the preferred organic cation of the ionic liquids for the extraction process. The extraction behaviors were investigated in detail, and the self-assembly samples were identified via SEM with mapping EDS, XPS, FT-IR and ESI-HRMS methods. All three ionic liquids showed excellent extraction efficiency for thorium and more than 99% of Th(IV) were extracted and solidified at two phase interface in a facile one-step process. The self-assembly extraction of Th(IV) exhibited the extremely excellent selectivity to Eu(III) and U(VI), and separation factors were up to 12000 for Th/Eu and more than of 3800 for Th/U, respectively. The proposed strategy not only develops an alternate method for the separation and enrichment of thorium ions, but also may pioneer the self-assembly extraction based on [DC18DMA]+ ionic liquids in the nuclear fuel cycle. Considered with the similarity of Pu(IV) and Th(IV), the one-step strategy may be extended for extraction and solidification of the key isotope Pu(IV) in nuclear industry.