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Effect of Structural Fe Reduction on Water Sorption by Swelling and Non-Swelling Clay Minerals

Vasilopanagos, Christos and Carteret, Cedric and Hillier, Stephen and Neumann, Anke and Brooksbank, Harry J. L. and Greenwell, Hugh Christopher (2022). Effect of Structural Fe Reduction on Water Sorption by Swelling and Non-Swelling Clay Minerals. Minerals. 12 :4 , 453
[Research article]

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Abstract

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 N-2 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.

Authors/Creators:Vasilopanagos, Christos and Carteret, Cedric and Hillier, Stephen and Neumann, Anke and Brooksbank, Harry J. L. and Greenwell, Hugh Christopher
Title:Effect of Structural Fe Reduction on Water Sorption by Swelling and Non-Swelling Clay Minerals
Series Name/Journal:Minerals
Year of publishing :2022
Volume:12
Number:4
Article number:453
Number of Pages:16
Publisher:MDPI
ISSN:2075-163X
Language:English
Publication Type:Research article
Article category:Scientific peer reviewed
Version:Published version
Copyright:Creative Commons: Attribution 4.0
Full Text Status:Public
Subjects:(A) Swedish standard research categories 2011 > 4 Agricultural Sciences > 401 Agricultural, Forestry and Fisheries > Soil Science
Keywords:adsorption, water vapour, BET, nitrogen, SSA, iron reduction, clay surface, nontronite, illite, smectites
URN:NBN:urn:nbn:se:slu:epsilon-p-117023
Permanent URL:
http://urn.kb.se/resolve?urn=urn:nbn:se:slu:epsilon-p-117023
Additional ID:
Type of IDID
DOI10.3390/min12040453
Web of Science (WoS)000785034900001
ID Code:27912
Deposited By: SLUpub Connector
Deposited On:17 May 2022 07:25
Metadata Last Modified:17 May 2022 07:31

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