sorption.
The standard free energy change, DG0
, DH0 and DS0 for
the interaction of Pb(II)-wheat bran was calculated from the
variations of the thermodynamic distribution coefficient, K0
with change in temperature. K0 for the adsorption reaction
was determined by plotting ln qe/Ce versus qe and
extrapolating to zero qe (Fig. 6). DG0 for the interaction
of wheat bran with Pb(II) was calculated as (6);
DG0 ZKRT ln K0 (6)
From the variations of DG0 with temperature, the
standard enthalpy, DH0 and entropy, DS0 were computed
using the following equation (Raji and Anirudhan, 1997)
(7):
DG0 Z DH0 KTDS0 (7)
The thermodynamic parameters are given in Table 6. The
positive values of DH0 suggest the endothermic nature of
the process. The values of DG0 which suggests that the
process is feasible and spontaneous with a high preference
of metal ions for wheat bran. The positive values of DS0
show the increased randomness at the solid/solution
interfaces during the adsorption of metal ions on wheat
bran and also reflects the affinity of the adsorbent material
for the metal ions under consideration. It is also suggested
that the positive values of entrophy indicate some structural
changes in the adsorbate and adsorbent (