Environmental Engineering Reference
In-Depth Information
(a)
(b)
3.0 × 10
-7
2.0 × 10
-7
1.0 × 10
-7
6.0 × 10
-8
5.0 × 10
-8
4.0 × 10
-8
3.0 × 10
-8
2.0 × 10
-8
1.0 × 10
-8
0.0
7.0 × 10
-8
S-NZVI
IONP
GNP
AgNP
6.0 × 10
-8
5.0 × 10
-8
4.0 × 10
-8
3.0 × 10
-8
2.0 × 10
-8
1.0 × 10
-8
0.0
1 h
4 h
12 h
24 h
72 h
1 h
4 h
12 h
24 h
72 h
Time (h)
Time (h)
FIGURE 37.9
Batch experiment results for the synthetic leachate metals: (a) Zn
2+
and (b) Pb
2+
removal behaviors while react-
ing leachate with S-NZVI, IONP, GNP, and AgNP solutions (1 g/l).
leachate by the production of OH
−
groups. An increase in OH
−
concentration is more favor-
able for metal hydroxide precipitation. In the case of GNP, the main mechanism may have
been adsorption.
37.3.7 Adsorption Isotherm Studies
Metal adsorptions were modeled with the Langmuir isotherm model given by Equation 37.7:
k
[]
[]
M
Γ
max
Γ
=
(
)
ads
(3 7. 7 )
1
+
k
M
where Γ
ads
is the removal capacity (mg/g); [M], the initial solution concentration (mg/l);
Γ
max
, the maximum adsorption capacity (mg/g); and
k
, the equilibrium constant for the
overall adsorption process. The Langmuir model assumes that all adsorption sites have
equal afinity for the adsorbate and therefore only monolayer adsorption occurs.
The Langmuir isotherm modeling data are tabulated in Table 37.3. According to the
adsorbed concentrations, the maximum Pb(II) adsorption density was recorded for IONP
TABLE 37.3
Langmuir Isotherm Model Data for Pb(II) and Zn(II) with S-NZVI, IONP, GNP, and AgNP at
pH 6.0
Langmuir Isotherm
Experiment
K
Γ
max
(mg/g)
R
2
S-NZVI
Zn(II)
18.4546
24.974
0.986
Pb(II)
6.7561
25.847
0.973
IONP
Zn(II)
2.9629
18.106
0.952
Pb(II)
1.8207
122.119
0.991
GNP
Pb(II)
0.2495
3.649
0.990
AgNP
Pb(II)
0.8651
5.436
0.994
