Environmental Engineering Reference
In-Depth Information
where b is the Langmuir constant and C
0
is the initial concentration of metal ions. The
value of R
L
indicated the types of Langmuir isotherm: irreversible (R
L
= 0), favorable (0
< R
L
< 1), linear (R
L
= 1), or unfavorable (R
L
> 1) (Kadirvelu et al., 2001). By
calculation, R
L
is always between 0 and 1 although very close to zero, regardless of the
initial concentration of metals. This result indicates that the uptakes of Cr(VI), Cu(II)
and Ni(II) by -Fe
2
O
3
are favorable.
Figure 9.22
Langmuir isotherms (Ce/qe vs. Ce) of Cr(VI), Cu(II) and Ni(II) adsorption
onto -Fe
2
O
3
nanoparticles.
Table 9.6
Langmuir constants for metal adsorption onto -Fe
2
O
3
nanoparticles (Hu et al.,
2006).
Langmuir Constants
R
2
R
L
*
Metal
pH
q
m
b
Cr(VI)
2.5
19.42
0.319
0.995
0.059
Cu(II)
6.5
26.95
0.446
0.999
0.043
Ni(II)
8.5
25.38
0.351
0.999
0.054
* R
L
is calculated at C
0
= 50 mg/L.
9.5.2.6 Desorption Studies
Since metal adsorption onto -Fe
2
O
3
is a physical process, it is possible for
regeneration or reactivation of the adsorbent. The adsorption of Cr(VI), Cu(II) and Ni(II)
on -Fe
2
O
3
is highly pH-dependent and hence desorption of metals is possible by
controlling the pH of the solution.
Search WWH ::
Custom Search