Reduction of Contaminants in Soil and Water By Direct Electric Current - Electrokinetics for Petroleum and Environmental Engineers - page 66

1

0.8

0.6

0.4

0.2

0

0 2

Pore volume of electroosmotic flow

1 3 4 5

Na, S = 81% Na, S = 53% Sr, S = 95%

Figure 2.24 Production of Na and Sr at cathode with pore voume of EO flow in
unsaturated clays (S: degree of saturation) (Pamukcu and Wittle, 1993)

contaminated with strontium and sodium show similar rates
of transport per pore volume of liquid despite the different
degrees of initial water saturation of the clay, as shown in
Figure 2.24 (also see Fig. 2.13 and 2.14). In all three cases,
majority of the contaminant is extracted into the cathode
before the water advances one full pore distance between
the anode and the cathode. However, the same may not
hold true for situations where electroosmotic advection is
the dominant mechanism of transport, as for non-aqueous
phase liquids. In those circumstances, continuous supply
of water at the influent electrode (anode-for cationic soils,
or soils with pH above PZC point; and cathode for anionic
soils, or soils with pH below PZC point) is expected to pro-
gressively provide sufficient water concentration in the pores
for the NAPLs to partition away from the solid surface.
H. Electrokinetic Extraction of Contaminants from Saturated
Soils:
Table 2.1 summarizes average metal concentration reduc-
tion (in percentage) in three replicate specimens of fully
saturated synthetic soils after 24 to 48 hours of EK treatment
of four selected heavy metals (Pamukcu and Wittle, 1993).
The measurements provided in the Table were taken at the
location of lowest concentration measurement along the
specimens, as observed in the spatial distribution of stron-
tium in Figure 2.25. Also shown in Table 1 is the average