Experimental and theoretical insights into the influence of gamma irradiation degradation products of N,N,N′,N′-tetraoctyl diglycolamide on extraction efficiency toward trivalent f-elements

[Display omitted] •The main γ-irradiation degradation products of TODGA (P1–P10) were identified and synthesized.•Different degradation products were found to exhibit very distinct roles during Eu(III) extraction.•The degradation product P2 resemblant in structure to TODGA offers the highest extraction ability among others.•The mechanisms of these degradation products for effecting Eu(III) extraction were elucidated on the molecular scale. Understanding the effect of radiation rays on N,N,N′,N′-tetraoctyl diglycolamide (TODGA) based solvent extraction systems is an essential task for establishing and optimizing related extraction processes in nuclear industries. However, the influence of various radiolysis degradation products on extraction efficiency and the mechanism involved still remain elusive. In this work, the radiolysis degradation products of TODGA were analyzed with the aid of high-performance liquid chromatography tandem mass spectrometry (HPLC-MS/MS) technique and documented results, followed by the successful synthesis of ten radiolysis degradation products P1–P10. The extraction ability of each main degradation product towards Eu(III) and their effects on the extraction performance of TODGA system were systematically studied. These radiolysis degradation products with diverse chemical structures were found to reveal different roles in extraction such as serving as co-extractant and synergist, in which P2 resemblance in structure to TODGA offers the highest extraction ability among others, thus mitigating the decrease of extraction efficiency. Mechanism investigations including slope analysis and density functional theory (DFT) calculations reveal that P2 is involved as one of the extracted species in the complexation with Eu(III) in its first coordination sphere. These findings provide in-depth experimental and theoretical guidance on the molecular scale for designing TODGA-based metal separation processes.