International Journal of Marine Science 2015, Vol.5, No.29, 1-7
5
Figure 6 Linear form of Freundlich isotherms of Cu(II), Pb(II)
on porcellanite at different temperatures
Figure 7 Linear form of Langmuir isotherms of Cu(II), Pb(II)
on porcellanite at different temperatures
ΔG = -RT lnk………………..…(4)
K = C
solid
/ C
liquid
……….……..(5)
lnK = ΔS / R – ΔH / RT……(6)
Where
G is the Gibbs energy change (KJ.mol
-1
), K is
the equilibrium constant, C
solid
is the solid phase
concentration at equilibrium (mg/l), C
liquid
is the liquid
phase concentration at equilibrium (mg/l), T is the
temperature in Kelvin and R is the gas constant (0.0083
KJ.mol
-1
K
-1
).
ΔH (KJ.mol
-1
) and ΔS (KJ.mol
-1
.k
-1
) can be calculated
from the slope and intercept of Eq.(6), respectively.
The Thermodynamic parameters at the studied
temperature ranges are listed in Table 2.
The plots of
lnK
versus. 1/T were found to be linear
with a correlation coefficient (R
2
= 0.871-0.977) and
(0.948-0.990) for adsorption of Cu(II) and Pb(II),
respectively (Figure 8).
Figure 8 Plot of van, t Hoff relationship between LnK versus
1/T
Table 2 indicate, ΔG at all temperatures were negative
and increrased with an increase in temperature,
indicating the spontaneity of the adsorption of Cu(II)
and Pb(II) onto porcellanite powder (Hefne
et al.,
2008). The positive value of ΔH indicates endothermic
nature of the adsorption process, while the positive
value of ΔS revealed the increase in randomness at the
solid/solution interface during the adsorption process
(Al-Saadie and Jassim, 2010).
3 Conclusion
The present study emphasize that porcellanite powder
was employed as an adsorbent for the removal of Cu(II)
and Pb(II) from aqueous solutions. The material
showed enhanced Cu(II) and Pb(II) adsorption
capacities compared with most materials reported in
literature. the equilibrium data followed Langmuir
