Iodine speciation in deep eutectic solvents

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 iodi...

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Bibliographic Details
Published in:Physical chemistry chemical physics : PCCP 2022-10, Vol.24 (39), p.2415-24115
Main Authors: Hartley, Jennifer M, Scott, Sean, Dilruba, Zarfishan, Lucio, Anthony J, Bird, Philip J, Harris, Robert C, Jenkin, Gawen R. T, Abbott, Andrew P
Format: Article
Language:English
Subjects:
Electrocatalysts
Electrochemistry
Fine structure
Hydrogen bonds
Iodine
Lactic acid
Leaching
Levulinic acid
Oxalic acid
Oxidation
Solvents
Speciation
X ray absorption
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Summary: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 I 2 Cl − /I 3 − (glycol and lactic acid systems), mixed I 3 − /I 2 (oxalic acid and urea systems), and singular I 3 − (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. Iodine speciation in deep eutectic solvents is affected by chloride activity, which is controlled by the hydrogen bond donor.
ISSN:1463-9076
1463-9084
DOI:10.1039/d2cp03185j