## 3 Results and Discussion
### Adsorption of Emergent Contaminants  
#### 3.2.1 Effect of Contact Time and Adsorption Kinetic  
We studied the adsorption efficiency of the two emerging contaminants while modifying the contact time 15, 30, 60, 90, 120 and 150 min. Samples for analysis were taken at regular time intervals to determine the percent removal of contaminants. The results obtained are shown in Figure 6.  
Figure 4: FTIR spectra of activated carbon from argon nutshells.  
Figure 5: (**a**) Nitrogen adsorption/desorption isotherms; (**b**) pore size distribution with insert in the region of pore diameter between 0 and 100 nm for AC based on argon nutshells.  
\begin{table}
\begin{tabular}{p{56.9 pt} p{56.9 pt} p{56.9 pt} p{56.9 pt} p{56.9 pt} p{56.9 pt}} \hline \hline \multirow{2}{*}{**Absorbent**} & **BET Surface Area (m\({}^{2}\)/g)** & **Dubinin-Radushkevich Surface Area (m\({}^{2}\)/g)** & **Dubinin-Sarkakov Surface Area (m\({}^{2}\)/g)** & **Total Pore Volume (m\({}^{2}\)/g)** & **Average Pore Diameter (nm)** \\ \hline AC obtained from argon & 1007.76 & 1063.70 & 1042.50 & 0.85 & 3.38 \\ \hline \hline \end{tabular}
\end{table}
Table 3: Textural properties of the activated carbons obtained from argon.  
adsorption kinetics of Caf and Dic showed that they were adsorbed rapidly at the investigated conditions, with equilibration already achieved at 90 min of contact for Dic and 60 min for Caf (Figure 6).  
The absorbance quantity of Dic and Caf at the equilibrium was 82% and 92%, with experimental uptake capacities of 82.60 mg/g and 93.09 mg/g, respectively.  
This information indicates that all adsorption data obtained after these times can be considered as obtained under equilibrium conditions. It is necessary to identify the step that governs the overall removal rate in the above adsorption process. The pseudo-first-order and pseudo-second-order kinetic models were tested to fit the experimental data obtained for Dic and Caf uptake by AC. The kinetic study results are given in Table 4.  
The kinetic data of Dic and Caf adsorption on AC based on organ nutshells was investigated at temperatures of 30 \({}^{\circ}\)C. The best fitting model was defined by the higher determination coefficient (R\({}^{2}\)). The pseudo-second-order model was the most suitable for the Dic and Caf adsorption on AC based on organ nutshells data because this model has a R\({}^{2}\) value close to 1 compared to pseudo-first-order model. The experimental adsorption capacity for Dic (91.16 mg/g) and for Caf (95.99 mg/g) was also close to the calculated adsorption capacity for Dic (82.60 mg/g) and for Caf (93.09 mg/g) (Figures 7 and 8). This suggests that the adsorption kinetics of emergent contaminants can be well described by the pseudo-second-order kinetic model. This means that the adsorption process is one of chemisorption with various interactions, such as electrostatic attractions, stacking (pi-stacking interactions (attractive, noncovalent interactions between aromatic rings)), hydrogen-bond formation, and Van der Waals forces between the adsorbent and adsorbate [88].  
\begin{table}
\begin{tabular}{c c c c c c c} \hline  & \multicolumn{3}{c}{**Pseudo First Order**} & \multicolumn{3}{c}{**Pseudo Second Order**} \\ \cline{2-7}  & **Qe (mg/g)** & \(\mathbf{K_{1}}\) & \(\mathbf{R^{2}}\) & **Qe (mg/g)** & \(\mathbf{K_{2}}\) & \(\mathbf{R^{2}}\) \\ \hline Dic & 41.01 & \(-\)0.00016 & 0.991 & 91.16 & 77576.79 & 0.999 \\ \hline Caf & 9.28 & \(-\)0.00016 & 0.872 & 95.99 & 463867.18 & 0.999 \\ \hline \end{tabular}
\end{table}
Table 4: Pseudo-first-order and pseudo-second-order parameters for adsorption of Dic and Caf onto AC based on organ nutshells.  
Figure 6: Adsorption of Dic and Caf onto AC based on organ nutshells at different temperatures (C\({}_{o}\) = 100 mg/L; m = 1 g; T = 30 \({}^{\circ}\)C; agitation speed = 200 rpm).