The thermodynamic parameters, including enthalpy change
DH, entropy change DS and Gibbs free energy change DG, could be
calculated according to the following equations [60].where DH is enthalpy change (J/mol), DS is entropy change (J/
mol K), DG is Gibbs free energy change (J/mol).
The data of lnKL versus 1/T were plotted and shown in Fig. 14.
There is a good linear relationship with the values of slope and
intercept determined to be 327.76 and 3.3851, respectively, and
the correlation coefficient R2 is 0.9999. The observed thermodynamic
values of DH, DS and DG were calculated and given in
Table 6. It can be seen from Table 6 that the negative values of DG
increase slowly with the decreasing of the temperature, revealing
that the adsorption process is spontaneous. The positive DS
indicate that the adsorption process is entropy driven rather than
enthalpy driven [61]. Furthermore, the positive value of DH also
confirms the endothermic nature of the adsorption on LSAC and
increasing temperature favors the adsorption process.