Alkylation and pre-organization of diglycolamide ligands on flexible platforms for nuclear waste treatment

Andrea Leoncini

Research output: ThesisPhD Thesis - Research UT, graduation UT

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Abstract

The research topic of this thesis concerns the synthesis and evaluation of new diglycolamide (DGA) ligands for the extraction and (potential) separation of actinide and lanthanide ions from bulk spent nuclear fuel. This work was aimed at the development of new pre-organised ligands with improved extraction and separation efficiency. This was done by focusing on the preparation of rather simple, easily accessible and completely incinerable ligands to be used in different processes in the nuclear waste industry.
Chapter 3 describes two new simple methods for the synthesis of DGAs, based on the Schotten-Baumann reaction and the Al(III)-catalysed direct amidation of esters. These reactions were also employed for the synthesis of some of the ligands studied in Chapter 4, which deals with small modifications of the backbone of TODGA (tetraoctyldiglycolamide) and its influence on the extraction and degradation behaviour of the ligands. Functionalisation of the TODGA backbone with alkyl chains exhibited increased selectivity and better stripping properties; comparison of the extraction properties of two diastereomeric ligands highlighted that even steric interactions between small methyl groups can have a significant impact on the performance of the ligands.
In Chapters 5 through 7, the synthesis of pre-organised DGA ligands and their extraction behaviour in molecular solvents and imidazolium-based ILs is reported. Tripodal ligands based on the flexible tris(N-alkylaminoethyl)amine platforms are described in Chapter 5, whereas generation-0 through generation-2 poly(propylene imine) dendritic platforms are used in Chapter 6, and DGA ligands based on the more rigid 1,3,5-trifunctionalised benzene platform are described in Chapter 7.
The results of the tripodal DGA ligands showed that the interplay between the platform and the solvent system is a fundamental contributor to the extraction properties and that, while pre-organisation provides a general increase in extraction efficiency, flexible platforms have the tendency to afford higher selectivity than rigid ones. RTIL systems proved their importance as a tool to modify the extraction behaviour, also via a change in extraction mechanism.
The results described in this thesis have the potential to lead to the development of more selective ligands for the separation of actinides and lanthanides and, ultimately, to more environmentally friendly reprocessing processes and long-term storage strategies.
Original languageEnglish
Awarding Institution
  • University of Twente
Supervisors/Advisors
  • Huskens, Jurriaan, Supervisor
  • Verboom, Willem, Co-Supervisor
Award date20 Dec 2017
Place of PublicationEnschede
Publisher
Print ISBNs978-90-365-4405-4
DOIs
Publication statusPublished - 20 Dec 2017

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