International Journal of Marine Science 2015, Vol.5, No.29, 1-7
4
It is 89.25 %, 97.43 % for 10 mg/l, 50 mg/l of Cu(II)
and Pb(II), respectively. At low initial concentrations
of metal ions nearly all the metal ions adsorbed due to
availability of active adsorption sites. As the metal
concentration increases active sites become occupied
and hence the less adsorption (Meena
et al., 2005).
Figure 4 Effect of initial concentration on adsorption of Cu(II),
Pb(II)
2.5
Adsorption isotherm
The adsorption of Cu(II), Pb(II) from aqueous solution
on porcelanite has been studied at different
temperatures (10, 25, 37.5 and 50
°
C). The general
shapes of Cu(II), Pb(II) adsorption isotherm are shown
in Figure 5 where the quantities adsorbed on porcelanite
(Qe) are plotted as a function of equilibrium
concentration (Ce) at (10, 25, 37.5 and 50
°
C).
Figure 5 Adsorption isotherm of Cu(II), Pb(II) on porcellanite
surface at different temperatures
The shape of the adsorption isotherm of Cu(II), Pb(II)
on porcellanite is consistent with H-type on the Giles
classification. H-type adsorption isotherm indicated
high affinity between Cu(II), Pb(II) and porcellanite
surface in very diluted solution (Giles et al., 1960). The
experimental adsorption data were applied to both the
theoretical Langmuir isotherm equation and empirical
Freundlich equation. The results of applying
Freundlich (eq.2) and Langmuir (eq. 3) (Veena and
Robert, 2002), isotherm on the adsorption data are
listed in Table 1.
Table 1 Results of the application of Freundlich and Langmuir isotherms on the system studied
Ion
Temp. (
C)
n
Kf
R2
Qm (mg/g)
b(L/g)
R2
Cu(II)
10.0
4.43
1.99
0.848
3.31
3.39
0.999
25.0
4.50
2.25
0.814
3.49
5.55
0.999
37.5
3.94
2.81
0.747
4.06
6.42
0.999
50.0
4.44
3.11
0.665
4.05
12.22
0.999
Pb(II)
10.0
2.79
3.89
0.956
23.18
0.08
0.998
25.0
3.00
4.86
0.971
24.38
0.11
0.998
37.5
3.13
5.76
0.943
24.97
0.18
0.999
50.0
3.31
7.17
0.917
26.68
0.27
0.999
log Qe = log Kf + 1/n log Ce……… (2)
Where Kf is a fanction of the adsorption capacity and n
is the intensity of adsorption.
Ce/Qe = 1/Qmb + Ce/Qm ………(3)
Where Qm is the maximum adsorption capacities
(mg/g) and b is related to the adsorption energy.
The Freundlich and Langmuir isotherms are applied
on the experimental data of the adsorption of Cu(II)
and Pb(II) ions on porcellanite by plotting log Q
e
versus log C
e
and
C
e
/Q
e
versus C
e
, respectively
(Figure 6 and 7). The results of Table 1 show that the
Langmuir isotherms is better fitted on this system than
the Freundlich as shown by the linear relationship of
(
C
e
/Q
e
) versus (C
e
) (Figure 7).
2.6
Thermodynamic studies
The effect of temperature on the adsorption of Cu(II)
and Pb(II) was studied in the range of 10-50
°
C using
different initial concentrations .The feasibitility of the
adsorption process can be estimated by the
Thermodynamic parameters of Gibbs energy change
(
G), enthalpy change (
H) and entropy change (
S)
by the following equations.
