Cryptand Cages for Anion Selective Encapsulation for Nuclear Waste
Lead Research Organisation:
University of Huddersfield
Department Name: Sch of Applied Sciences
Abstract
The reprocessing of spent fuels and the decommissioning of historical nuclear facilities generates a complex mixture of waste material that needs to rendered safe for long term storage and ultimate disposal. Some of the most difficult waste streams are those that contain oxyanions of toxic and radioactive elements, e.g. pertechnetate, selenite, selenate, chromate, molybdate, iodate, bromate.
We propose a cost-effective removal strategy based on a novel selective encapsulation process using self-assembled cryptand cages. A pilot study on common anions (with different charge and morphology) demonstrated a fast recovery, reducing anions concentration from 1000 to <0.1ppm. This research was published in the high-impact journal Angewandte Chemie in 2018, and patent protection is under way. The removal can be engineered to work in extreme environments, highly acidic solutions and high ionic strength, producing stable encapsulation of anions either in solution or as crystalline precipitates. This has an advantage for liquid high-level waste pending vitrification, as the anions will be stabilized within the highly radioactive liquor.
Our research vision is to attain controlled removal via immobilization using cryptand cages based on anion charge and morphology. Thus we need to determine the factors controlling the encapsulation and the precipitation: the nature of the cryptand (how changes in its design reflect in encapsulation), the metal center for the complex cage, the conditions of the liquid media (pH, ionic strength), and the kinetics of release.
To define this complex relationship, we will employ a multidisciplinary approach that brings together the power of computational screening, experimental synthesis and characterization. This will accelerate the development of sustainable and cost-effective encapsulation strategies, reduce environmental impact and enhance waste form performance.
We aim to support our hypothesis and to achieve the following objectives: (1) to synthetize ligands based on those previously reported but modulate the nature of the donor atoms and the size of the cavity, with a range of metal center to determine the factors controlling anion selectivity; (2) to identify the interactions between the cage and the anion to retard kinetic release; (3) to produce atomistic models of target structures using integrated experiments and modelling, and to characterize their stability, morphology, and composition.
We propose a cost-effective removal strategy based on a novel selective encapsulation process using self-assembled cryptand cages. A pilot study on common anions (with different charge and morphology) demonstrated a fast recovery, reducing anions concentration from 1000 to <0.1ppm. This research was published in the high-impact journal Angewandte Chemie in 2018, and patent protection is under way. The removal can be engineered to work in extreme environments, highly acidic solutions and high ionic strength, producing stable encapsulation of anions either in solution or as crystalline precipitates. This has an advantage for liquid high-level waste pending vitrification, as the anions will be stabilized within the highly radioactive liquor.
Our research vision is to attain controlled removal via immobilization using cryptand cages based on anion charge and morphology. Thus we need to determine the factors controlling the encapsulation and the precipitation: the nature of the cryptand (how changes in its design reflect in encapsulation), the metal center for the complex cage, the conditions of the liquid media (pH, ionic strength), and the kinetics of release.
To define this complex relationship, we will employ a multidisciplinary approach that brings together the power of computational screening, experimental synthesis and characterization. This will accelerate the development of sustainable and cost-effective encapsulation strategies, reduce environmental impact and enhance waste form performance.
We aim to support our hypothesis and to achieve the following objectives: (1) to synthetize ligands based on those previously reported but modulate the nature of the donor atoms and the size of the cavity, with a range of metal center to determine the factors controlling anion selectivity; (2) to identify the interactions between the cage and the anion to retard kinetic release; (3) to produce atomistic models of target structures using integrated experiments and modelling, and to characterize their stability, morphology, and composition.
Organisations
Studentship Projects
| Project Reference | Relationship | Related To | Start | End | Student Name |
|---|---|---|---|---|---|
| EP/R513234/1 | 01/10/2018 | 30/09/2023 | |||
| 2282151 | Studentship | EP/R513234/1 | 01/10/2019 | 30/09/2022 | Joseph Houghton |
| Description | The successful synthesis and characterization of a variety of organometallic complexes can be useful in a variety of application including environmental remediation and biomedical applications. Specific examples include tripodal ligands which can self-assemble into complexes to encapsulate anions, particularly phosphate, when in the presence of first row 2+ transition metals. Variations in the ligand structure result in certain complexes being more selective towards certain anions. In addition, (bipy)2RuL complexes were synthesized which, when subjected to visible wavelength light, undergo photocleavage with variation of the ligand changing the rate at which the complex undergoes photocleavage. Further, crown-based ligands have been shown to be double gated wherein the photocleavage can only proceed with irradiation by light and the presence of an anion/cation depending on the atoms making up the ring. |
| Exploitation Route | Further work could result in self-assembling complexes which can be tailored to specific applications. In environmental science, the selectivity to specific anions is helpful for the nuclear industry. In biomedical science, selectivity will greatly reduce the side effects of treatments and potentially being highly effective against even very aggressive diseases. Designing of complexes with specific photo-ejection will also have great applicability in medicine. Furthermore, self-assembling complexes capable of encapsulating anions could be added to water sources to remove excess anions such as phosphate and nitrate runoff from farming. |
| Sectors | Energy,Environment,Pharmaceuticals and Medical Biotechnology |