The influence of small pores on the anion transport properties of natural argillaceous rocks – A pore size distribution investigation of Opalinus Clay and Helvetic Marl

Wigger, Cornelia; Gimmi, Thomas; Muller, Arnaud; Loon, Luc R. Van (2018). The influence of small pores on the anion transport properties of natural argillaceous rocks – A pore size distribution investigation of Opalinus Clay and Helvetic Marl. Applied Clay Science, 156, pp. 134-143. Elsevier 10.1016/j.clay.2018.01.032

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The pore size distribution of two natural argillaceous rock samples, Opalinus Clay (OPA) and Helvetic Marl (HM) was investigated with five different methods: NMR, NMR cryoporometry, mercury intrusion porosimetry and CO2 adsorption, as well as N2 adsorption. Due to different physical principles of these methods different ranges of pore width could be detected, from micropores (<2nm) to mesopores (2-50nm) and macropores (>50nm). The aim was to shed light on the role of small pores on the transport properties of natural argillaceous rocks, in particular to explain the differences of anion diffusion in the two argillaceous rock samples. Knowing that Helvetic Marl exhibits a stronger anion exclusion than Opalinus Clay it was hypothesized that HM (with its smaller phyllosilicate and smectite content compared to OPA) has more interlayer equivalent (ILE) pores than OPA. ILE pores are defined as pores so narrow (<0.5nm) that diffuse double layers, formed at negatively charged surfaces, are overlapping. Accordingly, ILE pores behave similarly as interlayer pores and may block the anion diffusion. This study could not confirm the hypothesis that HM has more ILE pores. Similar pores size distributions were determined for both materials, even with a tendency of a larger fraction of small pores in OPA as compared to HM. However, all methods have limitations in the range of very small (nm) pores.

Item Type:

Journal Article (Original Article)

Division/Institute:

08 Faculty of Science > Institute of Geological Sciences
08 Faculty of Science > Institute of Geological Sciences > Rock-Water Interaction

UniBE Contributor:

Gimmi, Thomas

Subjects:

500 Science > 550 Earth sciences & geology

ISSN:

0169-1317

Publisher:

Elsevier

Language:

English

Submitter:

Thomas Gimmi

Date Deposited:

14 May 2018 11:40

Last Modified:

14 May 2018 11:40

Publisher DOI:

10.1016/j.clay.2018.01.032

Uncontrolled Keywords:

NMR, NMR cryoporometry, Gas adsorption, Mercury intrusion porosimetry, Opalinus Clay, Helvetic Marl

BORIS DOI:

10.7892/boris.116277

URI:

https://boris.unibe.ch/id/eprint/116277

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