## 3 Results and Discussion
### Sorption Study
\begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Sorbent** & **Cu (II) (mmol g\({}^{-1}\))** & **Pb (II) (mmol g\({}^{-1}\))** & **Cd (II) (mmol g\({}^{-1}\))** & **References** \\ \hline CS-ag-CM & & 0.88 & 1.49 & [40] \\ \hline Chitosan-Vanillin-Schiff base & & 0.11 & & [41] \\ Chitosan-O-Vanillin Schiff base & & 0.319 & & \\ \hline Chitosan-Schiff base & 1.74 & & & [42] \\ \hline PLLA/CH & 1.75 & & & [43] \\ \hline grafted crosslinked chitosan & & & & [43] \\ beads (G/ECH-CS) & 0.47 & 0.19 & 0.14 & [44] \\ \hline Modified chitosan beads & 2.21 & & 1.58 & [28] \\ \hline Glutaric acid modified Pb (II) & & & & \\ imprinted chitosan-based & & 0.36 & & [45] \\ composite membrane & & & & \\ \hline bentonite-chitosan composite & & 0.39 & 0.84 & [46] \\ \hline CH-ANP & 2.82 & 1.60 & 1.96 & Present Work \\ \hline \hline \end{tabular}
\end{table} 
Table 6: Comparison of chemically modified chitosan (CH-ANP) with the literature for divalent cations sorption (mmol g\({}^{-1}\)) from aqueous solution. \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Isotherm** & **Constant** & **Cu (II)** & **Pb (II)** & **Cd (II)** \\ \hline Freundlich & K\({}_{f}\) & 1.74 \(\pm\) 0.01 & 0.71 \(\pm\) 0.02 & 0.80 \(\pm\) 0.02 \\  & n & 3.37 \(\pm\) 0.02 & 1.72 \(\pm\) 0.03 & 2.46 \(\pm\) 0.03 \\  & R\({}^{2}\) & 0.916 & 0.985 & 0.951 \\  & SE & 0.59 & 0.03 & 0.35 \\  & \(\chi^{2}\) & 5.12 & 0.30 & 0.60 \\ \hline Temkin & K\({}_{\rm T}\) & 43.56 \(\pm\) 0.02 & 6.24 \(\pm\) 0.01 & 4.08 \(\pm\) 0.02 \\  & b & 0.879 \(\pm\) 0.01 & 2.46 \(\pm\) 0.03 & 1.39 \(\pm\) 0.01 \\  & R\({}^{2}\) & 0.970 & 0.970 & 0.991 \\  & SE & 0.08 & 0.05 & 0.04 \\  & \(\chi^{2}\) & 0.603 & 0.010 & 0.010 \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Isotherm results of tested divalent metal ions for their interaction with the chemically modified CH-ANP material. The results are based on a linear model of Freundlich and Temkin. (Abbreviations: K\({}_{f}\) (mmol g\({}^{-1}\)) and n—[PERSON] parameters, K\({}_{\rm T}\) (mmol dm\({}^{-3}\)), and b (kJ mol\({}^{-1}\))—Temkin parameters, r—correlation coefficients, and SE—standard errors). \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Isotherm** & **Constant** & **Cu (II)** & **Pb (II)** & **Cd (II)** \\ \hline \multirow{4}{*}{Langmuir} & N/ & 2.82 & - & - \\  & Ns & 2.96 \(\pm\) 0.01 & 1.87 \(\pm\) 0.01 & 3.50 \(\pm\) 0.03 \\  & b & 2.53 \(\pm\) 0.07 & 0.59 \(\pm\) 0.01 & 0.44 \(\pm\) 0.01 \\  & R\({}^{2}\) & 0.998 & 0.997 & 0.997 \\  & \(\chi^{2}\) & 0.001 & 0.003 & 0.0006 \\ Freundlich & K\({}_{f}\) & 1.84 \(\pm\) 0.08 & 0.81 \(\pm\) 0.04 & 0.88 \(\pm\) 0.04 \\  & n & 4.12 \(\pm\) 0.51 & 3.28 \(\pm\) 0.32 & 2.56 \(\pm\) 0.21 \\  & R\({}^{2}\) & 0.904 & 0.945 & 0.957 \\  & \(\chi^{2}\) & 0.062 & 0.007 & 0.01 \\ Temkin & K\({}_{\rm T}\) & 42.32 \(\pm\) 11.40 & 6.76 \(\pm\) 1.20 & 4.08 \(\pm\) 0.3 \\  & b & 1.94 \(\pm\) 0.11 & 2.57 \(\pm\) 0.31 & 1.39 \(\pm\) 0.05 \\  & R\({}^{2}\) & 0.964 & 0.980 & 0.992 \\  & \(\chi^{2}\) & 0.023 & 0.002 & 0.001 \\ \hline \hline \end{tabular}
\end{table} 
Table 5: Isotherm results of tested divalent metal ions for their interaction with the chemically modified CH-ANP material. The results are based on nonlinear Langmuir, Freundlich, and Temkin models. (Abbreviations: N/—number of sorbed moles (mmol g\({}^{-1}\)), Ns (mmol g\({}^{-1}\)), and b (g mmol\({}^{-1}\))—[PERSON] parameters, K\({}_{f}\)(mmol g\({}^{-1}\)) and n—Freundlich parameters, K\({}_{\rm T}\) (mmol dm\({}^{-3}\)), and b (kJ mol\({}^{-1}\))—Temkin parameters, r—correlation coefficients, and SE—standard errors).