# Study of the Ciprofloxacinacin Adsorption of Activated Carbon Prepared from Mangosteen Peel
## 3 Results and Discussion
### CIP Adsorption Thermodynamics of the ACMP  
The isometric potential variation (\(\Delta\text{G}^{0}\)), enthalpy (\(\Delta\text{H}^{0}\)), and entropy (\(\Delta\text{S}^{0}\)) of the adsorption process were calculated using the following equations:  
\[\text{K}_{\text{D}}=\frac{\text{q}_{\text{e}}}{\text{C}_{\text{cb}}} \tag{16}\]  
\[\Delta\text{G}^{0}=-\text{RTInK}_{\text{D}} \tag{17}\]  
\[\text{lnK}_{\text{D}}=-\frac{\Delta\text{G}^{0}}{\text{RT}}=-\frac{\Delta \text{H}^{0}}{\text{RT}}+\frac{\Delta\text{S}^{0}}{\text{R}} \tag{18}\]  
where K\({}_{\text{D}}\) is the equilibrium constant.  
The results of thermodynamic calculation on the CIP adsorption process of the ACMP are presented in Table 10.  
It can be seen in Table 10 that the free energy variation value (\(\Delta\text{G}^{0}\)) was determined as \(-\)0.845 to \(-\)5.329 kJ/mol and the entropy variation (\(\Delta\text{S}^{0}\)) was 0.223 kJ/mol, proving that the CIP adsorption of the ACMP was a spontaneous process. The enthalpy variation (\(\Delta\text{H}^{0}\)) was measured as 66.957 kJ/mol, verifying that the adsorption process was endothermic.  
During adsorption process, \(\Delta\text{H}^{0}\) < 25 kJ-mol\({}^{-1}\), and the van der Waals forces are majorly responsible for physical adsorption. If \(\Delta\text{H}^{0}\) = 40-200 kJ-mol\({}^{-1}\), the chemical bonding mainly leads to chemisorption [40]. The results of studying the CIP adsorption process of the ACMP follow the apparent second-order kinetics equation and the adsorption isotherm models of [PERSON], [PERSON], and [PERSON], indicating that the adsorption of the CIP on the ACMP can be dominated by chemisorption, which is in agreement with the calculation results of \(\Delta\text{H}^{0}\) = 66.957 of the CIP adsorption on the ACMP. The results of the thermodynamic calculation from the CIP adsorption process by the ACMP are similar to those reported by [PERSON] et al. [35], wherein the adsorption process of methylene blue in  
\begin{table}
\begin{tabular}{c c c c} \hline \hline
**T(K)** & \(\Delta\text{G}^{0}\) **(k)/mol** & \(\Delta\text{H}^{0}\) **(k)/mol** & \(\Delta\text{S}^{0}\)**(k)/mol\(\cdot\)K** \\ \hline
303 & \(-\)0.845 & & \\
313 & \(-\)2.696 & 66.957 & 0.223 \\
323 & \(-\)5.329 & & \\ \hline \hline \end{tabular}
\end{table}
Table 10: Thermodynamic parameters for the CIP adsorption.  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Concentration** & **Second-Order Kinetics** & **Constant k\({}_{2}\)** & **h** & **E (kJ/mol\(\cdot\)L)** \\
**CIP (mg/L)** & **Equation** & **(g/mg min)** & & \\ \hline
46.91 & t/q = 0.0627\(\cdot\)t + 0.2166 & 0.0182 & 4.62 & 13.72 \\
64.03 & t/q = 0.049\(\cdot\)t + 0.232 & 0.0103 & 4.31 & 14.96 \\
110.25 & t/q = 0.0356\(\cdot\)t + 0.1979 & 0.0064 & 5.05 & 16.53 \\ \hline \hline \end{tabular}
\end{table}
Table 9: Activation energy parameters.  
the environment on activated carbon materials made from mangosteen peel also exhibited an endothermic, spontaneous process which is governed by chemisorption. However, this is a different result from the results achieved by the authors when studying the CIP adsorption on biological activated carbon materials where they found that the adsorption process was a physical adsorption [7].