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Lookup NU author(s): Christos Vasilopanagos, Dr Anke Neumann, Dr Harry Brooksbank
This work is licensed under a Creative Commons Attribution 4.0 International License (CC BY 4.0).
© 2022 by the authors. Licensee MDPI, Basel, Switzerland. Ferruginous clay minerals in saturated soils and within hydrocarbon deposits often exist in a reduced state. Upon introduction of dissolved oxygen, or other oxidants, the clay minerals oxidise and changes in mineral surface charge and sorption capacity occur, resulting in changes in hydration as well as flux of intercalated species. Here we examine the sorption of water to the Fe-containing clay minerals nontronite NAu-2 (23 wt% Fe) and illite IMt-2 (7 wt% Fe) as a function of Fe oxidation state and exchangeable cations by means of water vapour volumetry and N2 surface area analysis. The clay minerals were chemically reduced using sodium dithionite. Sorption isotherms of water vapour and nitrogen, controlled relative humidity diffractograms, and chemical analyses were recorded. The results show that, after reduction using sodium dithionite, increased amounts of water vapour and nitrogen were adsorbed to the high Fe content nontronite, despite decreased interlayer separation. Little change was observed for the non-swelling and low Fe content illite. Sodium from the reducing agent was found to exchange with calcium present in the starting clay minerals, and sodium balanced the additional mineral charge generated during reduction. The findings presented in this study deliver improved understanding of sorption at the surface of the reduced clay minerals, which aid constrain the role of clay mineral interfaces in subsurface environments.
Author(s): Vasilopanagos C, Carteret C, Hillier S, Neumann A, Brooksbank HJL, Greenwell HC
Publication type: Article
Publication status: Published
Journal: Minerals
Year: 2022
Volume: 12
Issue: 4
Online publication date: 07/04/2022
Acceptance date: 28/03/2022
Date deposited: 21/04/2022
ISSN (electronic): 2075-163X
Publisher: MDPI
URL: https://doi.org/10.3390/min12040453
DOI: 10.3390/min12040453
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