Civil Engineering Reference
In-Depth Information
Stern Layer
Diffuse Layer
(Gouy Layer)
Plane of Shear
(a) Distribution of charges in the
vicinity of a colloidal particle
Stern Layer
0
Position of
Stern Ions
Plane of Shear
Z
p
Distance from
Particle Surface
(b) Distribution of potential in the
electrical double-layer
Fig. 10-3.
Stern's model for the electrical double layer
where:
Zp
zeta potential, millivolts
electrophoretic velocity, cm / s
viscosity, poise
constant
3.14159
D
dielectric constant of the liquid
The magnitude of the zeta potential is an approximate measure of colloidal particle
stability. Low zeta potentials indicate relatively unstable systems (particles tend to
coagulate), while a high zeta potential represents strong forces of separation (via elec-
trostatic repulsion) and a stable system (particles tend to suspend).
