Journal article
Coupled Multimodal Dynamics of Hydrogen-Containing Ion Networks in Water-Deficient, Sodium Hydroxide-Aluminate Solutions
The journal of physical chemistry. B, Vol.122(50), pp.12097-12106
12/20/2018
Handle:
https://hdl.handle.net/2376/102549
PMID: 30404445
Abstract
The (meta)stability of low water activity sodium hydroxide/aluminate (Na+OH–/Al(OH)4 –) electrolytes dictates kinetics in the Bayer process for aluminum refining and high-level nuclear waste processing. We utilized quasi-elastic neutron scattering (QENS) and proton nuclear magnetic resonance spectroscopy (1H NMR) in extremely concentrated sodium aluminate solutions to investigate the picosecond (ps) to microsecond (ms) timescale motions of H-bearing species (Al(OH)4 – monomers/clusters, OH– and H2O). In the QENS data, in contrast to typical liquids, no short-time translational diffusion was observed at 293 K, but two types of localized motions were found: (i) local backbone tumbling or a formation of large hydrated ion clusters on the order of 40–60 ps; and (ii) much slower, complex, and collective dynamics of the ensemble of H-bearing species on the order of 350–750 ps. Variable temperature, pulsed field gradient, diffusion-ordered 1H NMR was used to determine the ensemble translational motion along with relaxometry to calculate rotational correlation coefficients. The ensemble rotational correlation times were on the order of 184–300 ps from 1H NMR, which is consistent with the timescale of the QENS components. Complementary molecular dynamics simulation of NaOH solutions exhibit extensive ion networks potentially responsible for the observed dynamical coupling of water with the motion of large hydrated ion clusters. Understanding these collective motions will aid in predicting the behavior of complex solutions during aluminum production and during nuclear waste processing.
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Details
- Title
- Coupled Multimodal Dynamics of Hydrogen-Containing Ion Networks in Water-Deficient, Sodium Hydroxide-Aluminate Solutions
- Creators
- Trent R GrahamDavid Semrouni - Department of Chemistry and the Materials Science and Engineering ProgramEugene MamontovAnibal J Ramirez-CuestaKatharine PageAurora Clark - Department of Chemistry and the Materials Science and Engineering ProgramGregory K SchenterCarolyn I PearceAndrew G StackHsiu-Wen Wang
- Publication Details
- The journal of physical chemistry. B, Vol.122(50), pp.12097-12106
- Academic Unit
- Chemistry, Department of
- Publisher
- American Chemical Society
- Identifiers
- 99900546526201842
- Language
- English
- Resource Type
- Journal article