Diglycolamide with long C-chains combined with ether bonds for high loading of Am(III) and Eu(III): Extraction, aggregation, and third-phase formation studies

Abstract

Diglycolamide (DGA) extractants, especially TODGA (N,N,N′,N′‐tetraoctyl diglycolamide), show significant potential in high-level liquid waste treatment. However, their limited loading capacity for trivalent lanthanides (Lns) and actinides (Ans) often leads to detrimental emulsification or third phase formation, hindering their practical applicability. Herein, TOOEDGA (N,N,N’,N’-tetra(2-(octyloxy)ethyl)diglycolamide), a new DGA extractant with long C-chains combined with ether bonds, exhibits superior extraction performance towards Am³⁺ and Eu³⁺ in HNO₃ solution compared to TODGA. The factors influencing the formation of a third phase during the extraction process were investigated. It has been shown that TOOEDGA has a greater loading capacity for Lns³⁺ and can tolerate a wider concentration range of HNO₃. Additionally, the aggregation behavior of DGAs in n-dodecane was also studied using dynamic light scattering and small-angle X-ray scattering, revealing that the reverse micelles formed by TOOEDGA are more stable than those formed by TODGA. Moreover, under similar conditions, TOOEDGA molecules do not aggregate further to generate rod-like reverse micelle aggregates like those observed with TODGA, which is beneficial to inhibit the formation of the third phase. Consequently, our results suggest that TOOEDGA holds great promise as an alternative DGA extractant for practical industrial applications.