Reduction of Contaminants in Soil and Water By Direct Electric Current - Electrokinetics for Petroleum and Environmental Engineers - page 65

1.2

1

Cationic/NO 3

0.8

0.6

0.4

Cationic/Cl

0.2

Cationic/SO 4

0

0 50 100 150 200

Quantity of Electricity, Coulombs

Figure 2.23 Mass fraction of anions extracted into anode per Coulomb of electricity

electricity used. As expected, a linear trend prevails between
the extracted mass and the quantity of electricity required.
The anionic soil appears to display slightly higher efficiency
in energy requirement than the cationic soils for extraction
of anions. This is in line with the assumption that the anionic
soils will generate electroosmotic flow in the same direction
as the anion migration hence will be enhanced for the same
quantity of electricity when compared to that of the cationic
soil case.
G. Electrokinetic Extraction of Contaminants from Unsaturated
Soils :
The application of electrokinetics in the vadose zone has
been demonstrated by numerous studies in the past, most
notably by Mattson and co-workers (Mattson et al., 2002)
and by Banarjee and co-workers (Banerjee et al., 1987).
Unsaturated soils pose little difficulty when the electroki-
netic transport occurs by ion migration mostly. The mobile
ions residing in the liquid phase move to the respective
electrodes, provided that there is continuity of the liquid
phase over the diffuse layer interfaces. Since in most elec-
trokinetic treatment schemes, clean water is supplied at the
anode, the ionic constituents are eventually provided with
adequate solution water to migrate in during the course of
a treatment. The negative pore pressures that might gener-
ate in front or behind the water flux should have little effect
on the electromigration of these charged species. This phe-
nomenon is illustrated in the laboratory where kaolinite clay