## 3 Results and Discussion
### Resticide Adsorption Studies
#### 3.3.2 Isotherm Adsorption Studies
\begin{table}
\begin{tabular}{c c c c c c c c c c c} \hline \hline  & & & & & & & & & & & \\ \hline \multirow{2}{*}{**Sample**} & \multirow{2}{*}{**Pesticide**} & \multicolumn{3}{c}{**q\({}_{\text{exp}}\)**} & \multicolumn{3}{c}{**q\({}_{\text{tcer}}\)**} & \multicolumn{3}{c}{**q\({}_{\text{sat}}\times\mathbf{10^{-5}}\)**} & \multirow{2}{*}{**b**} & \multirow{2}{*}{**R\({}^{2}\)**} & \multirow{2}{*}{**q\({}_{\text{tcer}}\)**} & \multirow{2}{*}{**K\({}_{\text{F}}\)**} & \multirow{2}{*}{**n\({}_{\text{f}}\)**} & \multirow{2}{*}{**R\({}^{2}\)**} \\  & & **(mg/g)** & **(mg/g)** & **(mg/g)** & & & & & & & \\ \hline \multirow{2}{*}{**AC-ZnCl2**} & **ACT** & 128.9 & 112.9 & 8.86 & 3.1 & 0.955 & 115.3 & 1.98 & 0.9 & 0.959 \\  & **THM** & 126.8 & 149.5 & 8.99 & 4.2 & 0.875 & 126.3 & 59.16 & 4.9 & 0.978 \\  & **IMD** & 166.1 & 164.6 & 8.85 & 4.2 & 0.975 & 149.4 & 12.82 & 1.5 & 0.976 \\ \hline \multirow{2}{*}{**AC-FeCl3**} & **ACT** & 113.9 & 95.9 & 8.85 & 2.6 & 0.889 & 85.1 & 16.24 & 2.3 & 0.922 \\  & **THM** & 81.1 & 82.2 & 8.85 & 1.7 & 0.815 & 65.6 & 15.81 & 2.7 & 0.950 \\  & **IMD** & 104.1 & 103.6 & 8.85 & 2.6 & 0.960 & 92.3 & 11.71 & 1.9 & 0.969 \\ \hline \multirow{2}{*}{**AC-Fe(NO3)3**} & **ACT** & 60.6 & 34.2 & 8.87 & 0.8 & 0.768 & 37.6 & 0.04 & 0.6 & 0.793 \\  & **TIM** & 140.2 & 160.5 & 8.99 & 4.8 & 0.679 & 143.3 & 100.95 & 10.3 & 0.931 \\ \hline \multirow{2}{*}{**AC-Fe(NO3)3**} & **ACT** & 60.6 & 34.2 & 8.85 & 0.8 & 0.768 & 37.1 & 0.06 & 0.6 & 0.791 \\  & **TIM** & 140.2 & 160.5 & 8.99 & 4.8 & 0.678 & 143.3 & 100.95 & 10.3 & 0.931 \\ \cline{1-1}  & **IMD** & 55.8 & 38.7 & 8.85 & 0.9 & 0.899 & 42.4 & 0.08 & 0.6 & 0.925 \\ \hline \hline \end{tabular}
\end{table} 
Table 5: Isotherm model parameters for the adsorption of ACT, THM, and IMD onto the carbon materials: the Langmuir and Freundlich models. The best results in this work were obtained with the AC-ZnCl\({}_{2}\) activated carbon (S\({}_{\text{BET}}\) = 558 m\({}^{2}\)/g), with adsorption capacities of 128.9, 126.8, and 166.1 mg/g for ACT, IMD, and THM, respectively, at 24 h. When comparing the results obtained for AC-ZnCl\({}_{2}\) with those shown in Table 7, it can be seen that a higher adsorption capacity was obtained with the pesticide IMD when using sugarcane bagasse as a precursor, while for the pesticide ACT, lower adsorption capacity values were obtained; hence, it can be concluded that the adsorption capacity varies considerably depending on the origin of the activated carbon. On the other hand, if S\({}_{\text{BET}}\) values are considered, excluding that for the activated carbon from peach stones, the values were equal to or even higher than that found for the AC-ZnCl\({}_{2}\) activated carbon; however, the adsorption capacity and equilibrium time values were lower, except those for the activated carbon from sugarcane bagasse. Therefore, if the referenced studies did not allow enough contact time between the adsorbent and adsorbate, it is possible that saturation of the activated carbon did not occur, which would explain the very fast equilibrium times. For the activated carbon from sugarcane bagasse, the adsorption capacity was the highest (q\({}_{\text{e}}\) = 313 mg/g), and it took 720 min to reach the equilibrium. Furthermore, it should be noted that no literature results were found using the pesticide THM, which shows the innovativeness of this work. Furthermore, AC-ZnCl\({}_{2}\) outperformed all previously published adsorbents tested on ACT and outperformed three of four published adsorbents for IMD. In conclusion, more research is needed to determine the performance of this kind of adsorbent in pesticide removal.