Determination of diffusive transport in HDPy-montmorillonite by H ₂O-D₂O exchange using in situ ATR-FTIR spectroscopy

authored by

B. Schampera, S. Dultz

Abstract

The anion adsorption capability of clays can be improved significantly by modification with certain organic cations. However, surface properties and the microstructure of the clay might change and limit the use of organo-clays in barrier systems. In this study an experimental setup is introduced which allows the rapid determination of effective diffusion coefficients (D_eff) for H₂O in clay samples. H₂O→D₂O exchange experiments on hexadecylpyridinium (HDPy)-montmorillonite samples were performed in a diffusion cell attached to the ATR unit of a Fourier-transform infrared spectrometer. The mean D_eff for H₂O in a D ₂O-saturated original montmorillonite is 2.44×10^-11 m²/s in the bulk density range of 1.1-1.8 g/cm³. Hydrophobic surfaces increase the diffusivity only at high bulk densities in the saturated state. The mean D_eff is lower when HDPy is applied in amounts ≥80% of the cation exchange capacity in comparison with the original sample. At a saturation degree of the pores of 40%, D_eff for all samples is one order of magnitude less than in the saturated state. Results on D_eff obtained by ATR-FTIR spectroscopy are in good agreement with through-diffusion studies.

Organisation(s)

Institute of Soil Science
Section Soil Chemistry

Type

Article

Journal

Clay minerals

Volume

44

Pages

249-266

No. of pages

18

ISSN

0009-8558

Publication date

01.06.2009

Publication status

Published

Peer reviewed

Yes

ASJC Scopus subject areas

Geochemistry and Petrology

Electronic version(s)

https://doi.org/10.1180/claymin.2009.044.2.249 (Access: Unknown)