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1.0
C
o
= 1 mg L
-1
0.8
20
100
200
500
0.6
0.4
0.2
0
01234
5678
9 0
V/V
o
FIGURE 6.4
Effluent concentration distributions for different initial concentrations (
C
o
) using the second-
order model. (From H. M. Selim and M. C. Amacher. 1997.
Reactivity and Transport of Heavy
Metals in Soils
. Boca Raton, FL: CRC Press. With permission.)
isotherms in the low concentration range. Such a retention behavior has been
observed by several scientists for a number of reactive solutes. The simu-
lations also illustrate clearly the influence of the sorption maxima on the
overall shape of the isotherms. The influence of other parameters such as
F
,
k
3
, and
k
4
on retention kinetics can be easily deduced and is thus not shown.
Figures 6.4, 6.5, and 6.6 are selected simulations that illustrate the trans-
port of a reactive solute with the second-order model as the governing reten-
tion mechanism. The parameters selected for the sensitivity analysis were
ρ = 1.25 g cm
-3
, Θ = 0.4 cm
3
cm
-3
,
L
= 10 cm,
C
i
= 0,
C
o
= 10 mg L
-1
,
F
= 0.50,
and
S
max
= 200 mg kg
-1
. Here we assumed a solute pulse was applied to a
S
max
= 50 mg kg
-1
1.0
0.8
100
0.6
200
0.4
500
0.2
0
01234
5678
9 0
V/V
o
FIGURE 6.5
Effluent concentration distributions for different
S
max
values using the second-order model.
(From H. M. Selim and M. C. Amacher. 1997.
Reactivity and Transport of Heavy Metals in Soils
.
Boca Raton, FL: CRC Press. With permission.)
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