Geoscience Reference
In-Depth Information
Figure 7.5
Schmid theory of electroosmosis (
after
Das, 2008).
Table 7.1 k
e
of various clay soils (
after
Mitchell and Soga, 2005).
Soil type
k
e
(cm
2
s
−
1
V
−
1
)
London clay
5.8
×
10
−
5
Boston blue clay
5.1
×
10
−
5
5.7
×
10
−
5
Kaolin
Clay silt
5.0
×
10
−
5
Na-montmorillonite
2.0
×
10
−
5
to 12
×
10
−
5
where:
A
=
gross cross-sectional area perpendicular to water flow
i
e
=
applied electrical gradient
k
e
=
coefficient of electro-osmotic permeability
q
=
flow rate
Table 7.1 shows some typical values of
k
e
for several soils (Alshawabkeh
et al
.,
2004; Mitchell and Soga, 2005; Das, 2008).
Application of direct current through electrodes causes electrolysis reactions at the
electrodes (Acar
et al
., 1990; Cherepy and Wildenschild, 2003). Oxidation of water at
the anode generates an acid front and reduction at the cathode generates a base front.
Electrolysis reactions are described by Equations (7.4) and (7.5).
4e
−
→
4H
+
2H
2
O
−
O
2
↑+
(anode)
(7.4)
4e
−
→
4OH
−
4H
2
O
−
2H
2
↑+
(cathode)
(7.5)
