Abstract
Abstract Radiolytic stability of pillar[5]arene-based diglycolamides (P5DGAs) against gamma irradiation up to 1000 kGy adsorbed dose was studied. The results reveal the increase of radiation damage degree on P5DGAs with dose. The radiolysis products of P5DGAs including the gaseous and solid products were fully characterized by 1H NMR, HR-ESI-MS, GC, and HPLC techniques. It was found that the main radiolytic gas products of P5DGAs under argon are H2, N2, CO and gaseous hydrocarbons. The solid degradation products contain phenolic hydroxyl groups and secondary amine groups. In addition, solvent extraction toward Eu(III) was performed with P5DGAs, in which about 50% decrease on extraction efficiency was observed for irradiated P5DGAs with dose of 1000 kGy in comparison with the non-irradiated one. A radiolytic degradation pathway was also proposed based on the above results. This is the first time to investigate the radiolytic stability of neat P5DGAs and P5DGAs in molecular diluent in detail and provides useful information for further application of P5DGAs in practical applications for spent fuel reprocessing.
Highlights
Pillararenes, a new intriguing class of macrocycles discovered in 2008 by Ogoshi et al, have been the focus of considerable researches because of their facile synthesis, unique structural architectures, efficiency in metal ion Diglycolamides (DGAs) as multidentate extractants are considered to be one of the most efficient extractants for the separation of trivalent lanthanides and actinides from PUREX high active raffinates or dissolved spent nuclear fuel [11,12,13,14,15]
The radiolysis products of pillar[5]arene-based diglycolamides (P5DGAs) including the gaseous and solid products were fully characterized by 1H NMR, HR-Electrospray ionization mass spectrometry (ESI-MS), GC, and HPLC techniques
A series of diglycolamide-functionalized extractants such as DGA-functionalized task specific ionic liquids [16, 17], tripodal DGA (T-DGA) [18,19,20] and DGA-functionalized calix[4]arenes [21,22,23] have been extensively studied for Ln(III)/An(III) separation from acidic feeds
Summary
Pillararenes, a new intriguing class of macrocycles discovered in 2008 by Ogoshi et al, have been the focus of considerable researches because of their facile synthesis, unique structural architectures, efficiency in metal ion. Radiation on organic phase may result in radiolytic degradation of extractants, giving lower metals mass-transfer coefficients, reduced distribution ratios and separation factor due to the generation of unwanted complexing products, as well as deterioration of solvent performance. The radiolytic stability of P5DGAs in ionic liquids was reported by Arijit et al, they only investigated the effect of gamma irradiation on the Pu4+ extraction ability of P5DGAs/C8mimNTf2 systems. It was found that the P5DGAs/C8mimNTf2 systems are radiolytically stable for the extraction of Pu4+ and the extraction efficiency decreased by 51% at most after irradiation at a dose of 1000 kGy. To the best of our knowledge, no systematic study on radiolytic stability of neat P5DGAs or solutions of P5DGAs in molecular diluent 1-octanol has been reported, and the corresponding radiolysis mechanism still remains unknown [30]. This study represents the first attempt to study the radiolytic degradation of neat P5DGAs and P5DGAs in a molecular diluent
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