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Instruments / Technical Area	Publication Details	Published
I18-Microfocus Spectroscopy	Uptake and coordination behaviour of uranyl on functionalised silica J. T. M. Amphlett , S. E. Pepper , L. M. Harwood , K. R. Whittle , T. S. Lee , E. M. Moon , R. Joannes-Boyau , R. I. Foster , M. D. Ogden Colloids And Surfaces A: Physicochemical And Engineering Aspects 104 DOI: 10.1016/j.colsurfa.2024.134639 Diamond Proposal Number(s): [15769] Show Abstract ▼ Abstract: The safe decommissioning of nuclear reactors is a complex process, requiring a range of technological options for it to be done effectively. It has become more important in recent years, with the substantial number of reactors entering the decommissioning phase. This paper details the use of functionalised silica for the recovery of uranium from aqueous hydrochloric acid solutions, a potential agent for the treatment of steel reactor components during nuclear reactor decommissioning. Silica functionalised with either phosphonic acid, bistriazine, or bistriazinylbipyridine ligands was shown to extract uranium, with the commercially available phosphonic acid functionality being the most effective. Extractions of 100% were observed at [H+] ≤ 0.24 M, further the phosphonic acid functionality also had the highest loading capacity. Increasing [H+] has a suppressive effect on uranyl recovery, which was more pronounced for the in-house synthesized silica, and was attributed to protonation of the extracting moiety. Extended x-ray absorption fine structure spectroscopy was also used to determine the uranium coordination environments on the functionalised silica, and gain insights into the extraction mechanism. The uranyl cation was bound by two phosphonic acid groups, two bis-triazine groups, and one bistriazinylbipyridine group, respectively on each respective extractant. Uranyl was found to be penta-coordinate in the equatorial plane for all systems, with oxygen and/or chloride always present in the first coordination sphere. Evaluation of the mechanism indicated that uranyl must be loading onto the phosphonic acid functionality via multiple mechanisms, to both the phosphonic acid and silica related surface groups, although preferential binding of uranyl to the phosphonic acid groups was observed.	Jun 2024
B18-Core EXAFS	Insights on uranium uptake mechanisms by ion exchange resins with chelating functionalities: chelation vs anion exchange James T. M. Amphlett , Sungyeol Choi , Stephen A. Parry , Ellen M. Moon , Clint A. Sharrad , Mark D. Ogden Chemical Engineering Journal DOI: 10.1016/j.cej.2019.123712 Diamond Proposal Number(s): [12643] Show Abstract ▼ Abstract: X-ray absorption fine structure analysis has been successfully used to determine the coordination environment and therefore uptake mechanism towards the uranyl cation for a selection of commercially available ion exchange resins in non-saline and saline conditions ([Cl−] = 22.7 g L−1, 0.64 M) similar to those found in sea water. The resins tested were Purolite S985, S910 and S957, Dowex M4195, Ps-EDA, Ps-DETA and Ps-PEHA, which contain polyamine, amidoxime, mixed sulfonic/phosphonic acid, bispicolylamine, ethylenediamine, diethylenetriamine and pentaethylenehexamine functional groups, respectively. Purolite S910 and S957 were both found to extract the uranyl cation through a chelation mechanism. The uranium coordination environment on uranyl loaded Purolite S910 was found to be either tetra- or hexa-coordinate in the equatorial plane, with a 2:1 ratio of amidoxime:uranium in the fit suggesting either monodentate or η2 coordination by two amidoxime groups. The uranium environment for uranyl loaded Purolite S957 was found to be tetra-coordinate in the equatorial plane, with both sulfonic and phosphonic acid groups being involved in sorption. The presence of chloride in the loading solution had no effect on the uranyl coordination environment observed on any of the resins. In contrast, Dowex M4195, Purolite S985, Ps-EDA, Ps-DETA and Ps-PEHA exhibited an anion exchange mechanism for uranyl uptake as the corresponding extended X-ray absorption fine structure (EXAFS) data best fit a [UO2(SO4)3]4− structure.	Dec 2019
B18-Core EXAFS	Extraction of uranium from non-saline and hypersaline conditions using iminodiacetic acid chelating resin Purolite S930+ J. T. M. Amphlett , C. A. Sharrad , M. D. Ogden Chemical Engineering Journal 342, 133 - 141 DOI: 10.1016/j.cej.2018.01.090 Diamond Proposal Number(s): [12643] Show Abstract ▼ Abstract: Uptake behaviour of uranium from aqueous, acidic sulfate and chloride media on iminodiacetic acid chelating resin Purolite S930+ has been studied. Experiments have followed UO22+, Cu2+ and Fe3+ uptake behaviour with respect to acidic and ionic media type and concentration. Uptake suppression of all metals was observed at [H+] > 0.1 M sourced from H2SO4 and HCl. In contrast, significant uptake of Fe3+ was observed from solutions with [HCl] > 2 M. Suppression of UO22+ uptake (up to 15%) was observed upon increasing [SO42−] to 4 M, whilst negligible UO22+ uptake suppression was observed with [Cl−] up to 6 M. The impact of Fe3+ concentration on UO22+ extraction under hypersaline conditions ([Cl−] = 22.6 g L−1, 0.64 M) has been studied and behaviour fit to Langmuir and Dubinin-Radushkevich isotherms. Extended X-ray absorption fine structure (EXAFS) studies have been performed to assess the effect of salinity on the uranium coordination environment on the resin and therefore the mechanism of uptake. No change in surface species was observed, with the fit species being uranyl bound by the iminodiacetic acid functional group in a tridentate motif, with an associated bidentate sulfate group. An isotherm model based on this surface species has also been derived. It has been shown that at pH 2 there is little impact of increasing chloride and sulfate concentrations on the extraction behaviour of metals onto Purolite S930+ under the conditions tested. Rather, uranium uptake is more affected by the presence of Fe3+ in solution. As [Fe3+]/[UO22+] is increased from 0 to 2, UO22+ uptake is reduced by up to 66% at aqueous equilibrium.	Jun 2018
B18-Core EXAFS	Polyamine functionalised ion exchange resins: Synthesis, characterisation and uranyl uptake J. T. M. Amphlett , M. D. Ogden , R. I. Foster , N. Syna , K. Soldenhoff , C. A. Sharrad Chemical Engineering Journal DOI: 10.1016/j.cej.2017.11.040 Diamond Proposal Number(s): [12643] Show Abstract ▼ Abstract: A series of linear polyamine functionalised weak base anion exchange resins have been synthesised using the Merrifield resin and characterised using infra-red spectroscopy, thermogravimetry, elemental analysis and solid state 13C nuclear magnetic resonance spectroscopy. Uptake behaviour towards uranium (as uranyl) from sulfuric acid media has been assessed as a function of pH and sulfate concentration, with comparison to a commercially available weak base anion exchange resin, Purolite S985. Synthetic polyamine resins were seen to outperform the commercial resin at industrially relevant uranyl concentrations, with a trend of increased uptake being seen with increasing polyamine chain length. Uranium loading isotherm studies have been performed and fit with the Langmuir and Dubinin-Radushkevich isotherm models, with a maximum loading capacity observed being 269.50 mg g-1 for the longest polyamine chain studied. Extended X-ray absorption fine structure experiments have been used to determine uranium coordination environment on the resin surface, showing a [UO2(SO4)3]4- species. This coordination knowledge was employed to develop an extraction mechanism and derive an isotherm model based on the law of mass action.	Nov 2017

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