## 3 Results and Discussion
### Adsorption of Emergent Contaminants
#### 3.2.2 Adsorption Isotherm  
The adsorption isotherm study was done to describe the interactions between Dic and Caf on AC prepared from organ nutshells. It is important for the interpretation of the surface properties, the adsorption capacities of AC, and to complete the adsorption isotherm study that the equilibrium data were fitted to the Langmuir model and the Freundlich model [89; 90]. The Langmuir and Freundlich parameters of Dic and Caf adsorption on AC were calculated using Equations (S5) and (S6) in the Supplementary information. The isotherm parameters are listed in Table 5, Based on the comparison of the correlation coefficient (R2) values of Dic and Caf adsorbed on AC (Figures 9 and 10). Figure 8: Pseudo-second-order kinetic model applied to the adsorption of Caf (**a**) and Dic (**b**) on activated carbon from organ nutshells. \begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline  & \multicolumn{4}{c}{**Langmuir Isotherm**} & \multicolumn{4}{c}{**Freundlich Isotherm**} \\ \cline{2-7}  & **Q\({}_{\text{m}}\)(mg/g)** & **KJ (L/mg)** & **R2** & **R1** & **1/n** & **K\(\boldsymbol{\text{f}}\) (L/g)** & **R2** \\ \hline Dic & 126.16 & 0.24 & 0.99 & 0.17 & 1.50 & 38.19 & 0.85 \\ \hline Caf & 210.65 & 0.05 & 0.99 & 0.27 & 1.08 & 61.43 & 0.97 \\ \hline \hline \end{tabular}
\end{table} 
Table 5: Parameters of Langmuir and Freundlich models of Dic and Caf onto AC based on organ shells. Figure 7: Pseudo-first-order kinetic model applied to the adsorption of Caf (**a**) and Dic (**b**) on activated carbon from organ nutshells. Figure 9 describes the linear equations 1/Qe versus 1/Ce of Dic and Caf on AC based on organ nutshells. The Qm and Kl values are presented in Table 5, which show contaminants adsorption on the heat-resistant activated Langmuir angle and the calculated values of the parameters. Based on Table 5, the correlation coefficient of the linear regression equation (R\({}^{2}\)) of the Langmuir isotherm adsorption model is reasonable for the adsorption of Dic and Caf by activated carbon based on organ nutshells with values of 0.996, and 0.990, respectively. The maximum adsorption capacities (Qm) of Dic and Caf by activated carbon based on organ nutshells calculated from the Langmuir model are 126.16 mg/g, and 210.65 mg/g, respectively. When the experimental equilibrium data are appropriately described by the Langmuir model, it is essential to calculate the separation factor [91]. It was originally proposed that the essential characteristics of the Langmuir isotherm model could be indicated in terms of a dimensionless constant separation factor or equilibrium parameter Rl, which is defined as follows:  
\[\text{Rl}=\frac{1}{1+(\text{K}\ast\text{Co})} \tag{8}\]  
where Rl is a constant separation factor (dimensionless) of a solid-liquid adsorption system, Kl is the Langmuir equilibrium constant, and Co is the initial concentration. The results show that Rl values for Dic were 0.169 and for Caf 0.266. All of the values between zero and one indicate the suitability of the Langmuir isotherm model for the description of the adsorption process of Dic and Caf. Figure 10: Freundlich isotherm of Dic (**a**) and Caf (**b**) on AC based on organ nutshells. Figure 9: Langmuir isotherm of Dic (**a**) and Caf (**b**) on AC based on organ nutshells. Figure 10 describes the linear equation log (Qe) versus log (Ce), thereby determining the constants K_f_ and n, as shown in Table 5.  
Table 5 shows the adsorption process of Dic and Caf on activated carbon based on organ nutshells, according to the Freundlich isotherm model with values of 0.85 and 0.97, respectively. These indicate that the Freundlich isotherm model is not suitable for describing the contaminants adsorption process by the adsorbents. The results show that n values for Dic were 1.501 and for Caf were 1.076. They were both superior to one, indicating that the adsorption isotherms are poorly modelled by the Freundlich equation.