Environmental Engineering Reference
In-Depth Information
adsorption consists of capillary and condensation phenomena. In a transient regime,
various phenomena can be combined. At the beginning of a retention phenomenon
by sorption, the pollutant concentration in (on) the storing phase (the solid in the
figure) is a function of concentration in the feeding phase (generally the mobile
water phase) and increases with it. An increase of concentration in the water then no
longer allows an increase of the mass of pollutant fixed to the solid.
log C
solid
log C
Figure 13.2.
Pollutant retention at the surface of solid grains
Freundlich's relationship represents the phenomenon for moderate concentrations:
C
solid
= bC
m
[13.12]
Simplifying this to a linear relationship gives:
C
solid
= bC
[13.13]
where
b
and
m
are constant parameters.
The precise formulation of this type of relationship, as well as its degree of
reversibility, is dependent on geochemistry. The phenomena of precipitation, putting
in solution, biodegradation and lifetime (radioactive pollutants) make these
phenomena particularly complex. We will limit calculations to very simple relations
in this chapter.
The decrease in radioactivity and any form of pollutant degradation can be
expressed as:
&
S
=−
λ
[13.14]
p
