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Instruments / Technical Area	Publication Details	Published
B18-Core EXAFS	Tailoring lixiviant properties to optimise selectivity in E-waste recycling Jennifer M. Hartley , Sean Scott , Rodolfo Marin Rivera , Phil Hunt , Anthony J. Lucio , Philip Bird , Robert Harris , Gawen R. T. Jenkin , Andrew P. Abbott Rsc Sustainability 15 DOI: 10.1039/D2SU00038E Diamond Proposal Number(s): [26622] Open Access Show Abstract ▼ Abstract: The scale of E-waste production makes the selective recovery of technology metals an important research topic. It has previously been shown that deep eutectic solvents, DESs, can be used to rapidly digest gold and in the current study the effect of varying water and ethylene glycol content on the ability to selectively recover metals in DESs was investigated. It was found that increased water content resulted in an increase in metal etching rates for copper due to the decreasing viscosity of the solution, but etching rates of nickel, silver and gold were decreased due to the competition between chloride and oxide/hydroxide chemistry causing passivating films to form. Iodine was used as a catalyst and speciation was investigated in different solvent compositions. The ratio of the two trihalide species was mostly unaffected by solvent composition, but the presence of molecular iodine was detected with 20 wt% water due to decreased iodine solubility resulting from lower chloride concentration. It was determined that solvent physical properties were most important for metal etching rates at low water content, but at high water content the effect of oxide/hydroxide chemistry was more significant, resulting in the possibility of selective metal etching of copper from PCBs.	Nov 2022
B18-Core EXAFS	Iodine speciation in deep eutectic solvents Jennifer M. Hartley , Sean Scott , Zarfishan Dilruba , Anthony J. Lucio , Philip J. Bird , Robert C. Harris , Gawen R. T. Jenkin , Andrew P. Abbott Physical Chemistry Chemical Physics 114 DOI: 10.1039/D2CP03185J Diamond Proposal Number(s): [26622] Open Access Show Abstract ▼ Abstract: Iodine has been shown to act as a good electrocatalyst for metal digestion in deep eutectic solvents (DESs) but little is known about its speciation or reactivity in these high chloride containing media. Extended X-ray absorption fine structure (EXAFS) spectroscopy measurements were made at the iodine K-edge in a range of DESs with different glycolic or acidic hydrogen bond donors (HBDs), along with examining the effect of iodine concentration between 0.01 and 0.5 mol dm−3. Three groups of speciation were detected: mixed I2Cl−/I3− (glycol and lactic acid systems), mixed I3−/I2 (oxalic acid and urea systems), and singular I3− (levulinic acid system). UV-vis spectroscopy was used to confirm the speciation. Electrochemistry showed that iodine redox behaviour was unaffected by the changing speciation. Leaching data showed that metal oxidation was related not only to changing iodine speciation, but also the reactivity and coordination ability of the HBD.	Sep 2022
B18-Core EXAFS	EXAFS study into the speciation of metal salts dissolved in ionic liquids and deep eutectic solvents Jennifer Hartley , Chung-Man Ip , Gregory Forrest , Kuldip Singh , Steve Gurman , Karl S. Ryder , Andrew P. Abbott , Gero Frisch Inorganic Chemistry 53 (12) DOI: 10.1021/ic500824r Diamond Proposal Number(s): [6342, 6344, 7437] Show Abstract ▼ Abstract: The speciation of metals in solution controls their reactivity, and this is extremely pertinent in the area of metal salts dissolved in ionic liquids. In the current study, the speciation of 25 metal salts is investigated in four deep eutectic solvents (DESs) and five imidazolium-based ionic liquids using extended X-ray absorption fine structure. It is shown that in diol-based DESs MI ions form [MCl2]− and [MCl3]2 complexes, while all MII ions form [MCl4]2 complexes, with the exception of NiII, which exhibits a very unusual coordination by glycol molecules. This was also found in the X-ray crystal structure of the compound [Ni(phen)2(eg)]Cl2·2eg (eg = ethylene glycol). In a urea-based DES, either pure chloro or chlorooxo coordination is observed. In [C6mim][Cl] pure chloro complexation is also observed, but coordination numbers are smaller (typically 3), which can be explained by the long alkyl chain of the cation. In [C2mim][SCN] metal ions are entirely coordinated by thiocyanate, either through the N or the S atom, depending on the hardness of the metal ion according to the hard-soft acid-base principle. With weaker coordinating anions, mixed coordination between solvent and solute anions is observed. The effect of hydrate or added water on speciation is insignificant for the diol-based DESs and small in other liquids with intermediate or strong ligands. One of the main findings of this study is that, with respect to metal speciation, there is no fundamental difference between deep eutectic solvents and classic ionic liquids.	Jun 2014
B18-Core EXAFS	Ligand exchange in ionic systems and its effect on silver nucleation and growth Andrew P. Abbott , Muhammad Azam , Gero Frisch , Jennifer Hartley , Karl Scott Ryder , Saima Saleem Physical Chemistry Chemical Physics DOI: 10.1039/c3cp52674g Show Abstract ▼ Abstract: The electrodeposition of metals from ionic solutions is intrinsically linked to the reactivity of the solute ions. When metal salts dissolve, the exchange of the anion with the molecular and ionic components from solution affects the speciation and therefore the characteristics of metal reduction. This study investigates the nucleation mechanism, deposition kinetics, metal speciation and diffusion coefficients of silver salts dissolved in Deep Eutectic Solvents. The electrochemical reduction of AgCl, AgNO3 and Ag2O is studied in 1:2 choline chloride:ethylene glycol and 1:2 choline chloride:urea. Cyclic voltammetry is used to evaluate electrochemical kinetics. Detailed analysis of chronoamperometric data shows that silver deposits form via multiple 3D nucleation with mass transport controlled hemispherical growth. The nucleation mechanism was found to be potential dependent, varying from progressive to instantaneous as the reduction potential becomes more cathodic. Diffusion coefficients are determined using three different methods. Trends are rationalised in terms of solvent viscosity and silver speciation analysis with EXAFS. The morphology of electroreduced silver is investigated with scanning electron microscopy and shows that deposits from the urea based liquid form more dense morphologies than those from the ethylene glycol based liquid.	Aug 2013

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