## 3 Results and Discussion
### Adsorption of Emergent Contaminants
#### 3.2.3 Effect of Temperature and Thermodynamic Study  
The effect of temperature on the adsorption phenomenon was studied by varying this parameter from 10 \({}^{\circ}\)C to 30 \({}^{\circ}\)C using a thermostat bath to maintain the temperature at the \begin{table}
\begin{tabular}{c c c c c} \hline \hline \multirow{2}{*}{**adsorbent**} & \multirow{2}{*}{**Contaminants**} & **BET Surface Area** & \multicolumn{2}{c}{**Adsorption Capacity**} \\  & & **(m\({}^{2}\)/g)** & **(mg/g)/Removal** & **References** \\ \hline \multirow{2}{*}{AC based on Organ nutshells} & Dic & & 126 & \\ \cline{2-5}  & Caf & & 210 & Present work \\ \hline AC-HP & BPA & 1372 & 1250 & [92] \\ \hline \multirow{2}{*}{ACH} & DCF & & 149 & \\ \cline{2-5}  & PARX & & 168 & [93] \\ \hline ANS & BPA & 42 & 1162 & [94] \\ \hline ANS & CV & - & 98.21\% & [95] \\ \hline \hline \end{tabular}
\end{table} 
Table 6: Adsorption capacities and surface area of different contaminants using AC based on organ fruits shells compared to the literature data. desired value. The tests were carried out by stirring 1 g of activated carbon based on organ shells with 100 mg of each contaminant (diclofenac and caffeine) in 1 L of the solution. Initially, thermodynamic parameters such as Gibbs free energy (\(\Delta\)G\({}^{\circ}\)), enthalpy (\(\Delta\)H\({}^{\circ}\)), and entropy (\(\Delta\)S\({}^{\circ}\)) for diclofenac and caffeine adsorptions were determined by the slope and intercept in Ln(K) versus 1/T plot (Figure 11) that allowed for calculating the values of \(\Delta\)H\({}^{\circ}\) and \(\Delta\)S\({}^{\circ}\) in both matrices. The results are shown in Table 7.  
The negative values of the three parameters \(\Delta\)H\({}^{\circ}\), \(\Delta\)G\({}^{\circ}\), and \(\Delta\)S\({}^{\circ}\) of diclofenac indicate that the reaction is spontaneous and exothermic and that the order of distribution of the contaminant molecules on the adsorbent is large compared to that in solution. Furthermore, an examination of the standard enthalpy values of the adsorption (<40 kJ/mol) shows that it is physisorption. In the case of diclofenac, the negative \(\Delta\)S\({}^{\circ}\) value shows that adsorption occurs with increasing order at the solid-solution interface. The negative values of \(\Delta\)G\({}^{\circ}\) increase with temperature and indicate an increase in disorder during adsorption, and the randomness increases at the solid-solution interface during this binding process. This can be explained by the redistribution of energy between the absorbent and the absorbate. The positive value of \(\Delta\)H\({}^{\circ}\) confirms the endothermic nature of the adsorption process of caffeine (values lower than 40 Kj/mol). Therefore, the adsorption regarding the matrices occurs by physisorption. Indeed, \(\Delta\)S\({}^{\circ}\) presented positive values, which agrees with a dissociative mechanism. Moreover, the positive value of \(\Delta\)S\({}^{\circ}\) shows the increased randomness at the solid-solution interface during the adsorption. It might display an increment of the degrees of freedom for the caffeine molecules in the solution. Additionally, Table 7 shows more negative \(\Delta\)G\({}^{\circ}\) values as the temperature increased; these indicate that the adsorption process is spontaneous, and spontaneity increases with an increase in temperature. \begin{table}
\begin{tabular}{c c c c c c} \hline \hline \multirow{2}{*}{**Contaminants**} & \multirow{2}{*}{**T** (\({}^{\circ}\)**C**)} & \(\Delta\)G\({}^{\circ}\) & \(\Delta\)H\({}^{\circ}\) & \(\Delta\)S\({}^{\circ}\) & \multirow{2}{*}{**R\({}^{2}\)**} \\  & & **(Kj/mol)** & **(Kj/mol)** & **(Kj/mol/k)** & **(Kj/mol/k)** \\ \hline \multirow{3}{*}{Dic} & 10 & \(-\)3.28 & & & \\ \cline{2-6}  & 20 & \(-\)3.07 & \(-\)20.11 & \(-\)59.32 & 0.82 \\ \cline{2-6}  & 30 & \(-\)1.85 & & & \\ \hline \multirow{3}{*}{Caf} & 10 & \(-\)3.29 & & & \\ \cline{2-6}  & 20 & \(-\)3.51 & 1.77 & 17.95 & 0.92 \\ \cline{2-6}  & 30 & \(-\)3.64 & & & \\ \hline \hline \end{tabular}
\end{table}