ORIGINAL PAPER
Bentonite electrical conductivity: a model based on series–parallel
transport
Ana T. Lima
•
J. P. Gustav Loch
•
Pieter J. Kleingeld
Received: 10 September 2009 / Accepted: 21 December 2009 / Published online: 30 January 2010
Ó The Author(s) 2010. This article is published with open access at Springerlink.com
Abstract Bentonite has significant applications nowa-
days, among them as landfill liners, in concrete industry as
a repairing material, and as drilling mud in oil well con-
struction. The application of an electric field to such
perimeters is under wide discussion, and subject of many
studies. However, to understand the behaviour of such an
expansive and plastic material under the influence of an
electric field, the perception of its electrical properties is
essential. This work serves to compare existing data of
such electrical behaviour with new laboratorial results.
Electrical conductivity is a pertinent parameter since it
indicates how much a material is prone to conduct elec-
tricity. In the current study, total conductivity of a com-
pacted porous medium was established to be dependent
upon density of the bentonite plug. Therefore, surface
conductivity was addressed and a series–parallel transport
model used to quantify/predict the total conductivity of the
system.
Keywords Bentonite Á Series–parallel transport Á
Electrical conductivity Á Surface conductivity
1 Introduction
Bentonite is a type of clay consisting predominantly of
smectite minerals, usually montmorillonite and beidellite,
described by Coban and Ece [1] and Sposito [2] and was
first described by Knight [3] as a highly plastic and highly
weathering resistance material. This particular type is
highly swelling in the presence of moisture, and its large
double-layer (DL) is convenient for the retention of cat-
ions, toxins, etc. Because of this particular feature, ben-
tonite is widely used for different purposes. The uses are as
wide as clarification of wine and beer [4], as beauty
products, confinement of hazardous, nuclear and radioac-
tive wastes e.g. [5, 6], as geosynthetic clay liner, and some
bentonite cross applications with concrete for retention of
contaminants in waste solidification/stabilization tech-
niques were also proposed e.g. [7].
When debating the properties of a compacted bentonite
liner or plug, the differences are significant from the material
in suspension. Several studies have been carried out to
understand the behaviour of particular species in compacted
bentonite plug, where double-layers (DL) are overlapping
since they are so thick. Kozaki et al. [8] and Bourg et al.
[9, 10] are some examples of studies of diffusivity of ions in
compacted sodium bentonites. Electrical conductivity of
colloids and clay-rich porous materials is a pertinent
parameter when studying electrokinetic applications.
Electrokinetic (EK) barriers are an example where an
electric field is applied to clay liners in order to retain
contaminants in them [11, 12]. Also, EK has previously
been proposed for monitoring synthetic geoclay liners [13]
and in 2004 a patent has been created for the EK treatment
of landfill clay liners (US Patent 6736568—Electrokinetic
geosynthetic structure).
EK is a technique which has been widely used, from the
stabilization of quick clays [14] to the decontamination of
polluted soil e.g. [15]. EK has been tested for the reme-
diation of contaminated matrixes with organic, inorganic
and radionuclide’s species [15] and is particularly suited in
the treatment of fine-grained, highly organic or argillaceous
soils, with high water content [16]. The conduction of
A. T. Lima (&) Á J. P. G. Loch Á P. J. Kleingeld
Department of Earth Sciences, Geochemistry, Faculty
of Geosciences, Utrecht University, PO Box 80.021,
3508 TA Utrecht, The Netherlands
e-mail: lima.at@gmail.com; a.lima@geo.uu.nl
123
J Appl Electrochem (2010) 40:1061–1068
DOI 10.1007/s10800-009-0060-7