Skip to main content
Research article - Peer-reviewed, 2022

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

Vasilopanagos, Christos; Carteret, Cedric; Hillier, Stephen; Neumann, Anke; Brooksbank, Harry J. L.; Greenwell, Hugh Christopher;

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.

Keywords

adsorption; water vapour; BET; nitrogen; SSA; iron reduction; clay surface; nontronite; illite; smectites

Published in

Minerals

2022, volume: 12, number: 4, article number: 453
Publisher: MDPI

Authors' information

Vasilopanagos, Christos
Durham University
Carteret, Cedric
Universite de Lorraine
James Hutton Institute
Swedish University of Agricultural Sciences, Department of Soil and Environment
Neumann, Anke
Newcastle University - UK
Brooksbank, Harry J. L.
Newcastle University - UK
Greenwell, Hugh Christopher
Durham University

UKÄ Subject classification

Soil Science

Publication Identifiers

DOI: https://doi.org/10.3390/min12040453

URI (permanent link to this page)

https://res.slu.se/id/publ/117023