Investigation on the recovery of thorium and rare earth from radioactive waste residue by functionalized ionic liquids.

A recyclable IL separation strategy is provided, which simplifies the separation process of Th and RE, reduces chemical consumption, and provides a new idea for the treatment of IATREO waste residue. [Display omitted] • Efficient and sustainable separation of thorium and rare earth achieved using a novel ionic liquid. • The separation factor of Th/REs is as high as 22114. • Functionalization of cations provides more coordination sites to form an ion pair. • Stripping and recycling process of [OB2DTA][CA12] is easier to implement. • REs loss was limited to less than 0.3%, with Th and Fe extraction efficiencies of 99.5% and 100%, respectively. Thorium (Th) containing radioactive waste generated by ion-adsorbed rare earth ore (IATREO) separation plants poses a threat to the environment. The waste residue contains a much higher content of rare earth (RE) than the original IATREO. This study describes novel ionic liquids (ILs) containing cationic functionalization and evaluates their effectiveness in recovering Th and RE from the waste residue leaching solution (WRLS). Di-functionalization of the cation in ILs is more advantageous than mono-functionalization and non-functionalization, providing more coordination sites and achieving higher extraction and separation performance. In the simulated solution at an initial pH of 3, [OB2DTA][CA12] is able to extract 99.0% of Th and only 0.4% of RE, the Th/RE separation factor reaches 22114. The extraction reaction is carried out by an ion association mechanism. After 5 cycles of extraction-stripping-regeneration, the extraction and separation abilities of ILs remain stable. For the HCl leaching solution of waste residue, 99.5% of Th is separated in two extraction stages, while the total loss of RE is only about 15 mg/L. The recyclable separation strategy based on ILs simplifies the separation process of Th and RE, reduces chemical consumption, and provides a new idea for the treatment of IATREO waste residue. [ABSTRACT FROM AUTHOR]