Environmental Engineering Reference
In-Depth Information
Cations
Anions
Distance
Figure 7.8.
Distribution of ions adjacent to a clay surface according to the concept of the diffuse dou-
ble layer (Mitchell, 1976).
Figure 7.9.
Variation in electrical potential with distance from the clay surface (Adapted from Mitchell,
1976).
The resulting electrical potential varies with distance from the clay surface as shown in
Figure 7.9. The potential is negative, reflecting the large negative charge on the clay surface.
7.3.4
Mechanism of dispersion
When two clay particles come near each other, the potential fields overlap, leading to
repulsion if the particles are close enough. These repulsive forces are counteracted by Van
der Waal's attractive forces as shown in
Figure 7.10
. If the repulsive forces are greater
