## 3 Results
### Adsorption of AsO\({}_{4}\)\({}^{3-}\) on Source Materials and Composite Adsorbents
The adsorption isotherms (Figure 7) calculated according to Equation (3) (page 3) supported the above aspects. The data obtained by the Pb\({}^{2+}\) adsorption on all composite adsorbents (Figure 7a) could be fitted by the [PERSON] and Freundlich models, and the \begin{table}
\begin{tabular}{c c c c c c c c c c} \hline  & \multicolumn{3}{c}{**Langmuir Model**} & \multicolumn{3}{c}{**Freundlich Model**} & \\  & \(q_{\rm max}\) & \(Q_{t}\) & \(K_{L}\) & \(R^{2}\) & \(q_{\rm max}\) & \(n\) & \(K_{\rm F}\) & \(R^{2}\) & \(\Delta G\) \\  & **(mmol g\({}^{-1}\))** & **(mmol g\({}^{-1}\))** & **(Lmmol\({}^{-1}\))** & **(mmol g\({}^{-1}\))** & **(mmol g\({}^{-1}\))** & **(mmol g\({}^{-1}\))** & **(kmol g\({}^{-1}\))** & **(kmol g\({}^{-1}\))** \\ \hline
**SK** & 0.005 & - & - & - & 0.005 & - & - & - & - \\
**KB** & 0.02 & 0.02 & 331.4 & 0.819 & 0.02 & 0.21 & 0.05 & 0.940 & \(-\)14.4 \\
**KF** & 0.02 & 0.02 & 720.8 & 0.920 & 0.02 & 0.14 & 0.04 & 0.788 & \(-\)16.3 \\
**SK+KB** & 0.03 & 0.04 & 7.37 & 0.948 & 0.02 & 0.55 & 0.05 & 0.957 & \(-\)5.0 \\
**SK+KF** & 0.01 & - & - & - & 0.01 & - & - & - & - \\ \hline \end{tabular}
\end{table} 
Table 6: Parameters of Langmuir and Freundlich models for AsO\({}_{4}\)\({}^{3-}\) adsorption. Figure 6: Efficiency of AsO\({}_{4}\)\({}^{3-}\) adsorption on source materials and composite adsorbents. experimental adsorption capacities were comparable for the adsorbents prepared under different conditions (T, A). On the other hand, only the adsorption of AsO\({}_{4}\)3\({}^{-}\) on SK-KB and SK-KB-T proceeded according to the adsorption models (Figure 7b) with a higher sorbability of AsO\({}_{4}\)3\({}^{-}\) on SK-KB-T. As follows from Tables 7 and 8, the correlation factors \(R^{2}\) of both the Langmuir and Freundlich fits rather indicated the decreasing equilibrium of the adsorption process with an increased preparation temperature. As evident from the graph in Figure 8, the growing preparation temperature of the composites did not affect the adsorption yield of Pb2+, but noticeably inhibited AsO\({}_{4}\)3\({}^{-}\) adsorption. This phenomenon was apparently related to surface changes. Elevated temperatures, and especially exposure to high temperatures in the autoclave, could cause binding changes in the active sites on the adsorbent surface. \begin{table}
\begin{tabular}{c c c c c c c c c c c} \hline  & & & \multicolumn{3}{c}{**Langmuir Model**} & \multicolumn{3}{c}{**Freundlich Model**} \\  & **Preparation** & \(q_{\text{max}}\) & \(Q_{\text{t}}\) & \(K_{\text{L}}\) & \(q_{\text{max}}\) & \(K_{\text{F}}\) & & & \\  & **Temperature** & **(mmol & **(mmol & **(mmol & **(mmol & **(mmol & **(mmol & **(mmol & **(mmol & **(mmol & **(kJ.mol\text{-})})\) \\  & **g\({}^{-1}\))** & **g\({}^{-1}\))** & & & & & & & \\ \hline
**SK+KB** & 20 \({}^{\circ}\)C & 0.50 & 0.57 & 512.1 & 0.933 & 0.50 & 0.80 & 50.90 & 0.980 & \(-\)15.5 \\  & 65 \({}^{\circ}\)C & 0.30 & 1.23 & 74.8 & 0.992 & 0.30 & 0.91 & 71.74 & 0.985 & \(-\)11.4 \\  & 110 \({}^{\circ}\)C & 0.48 & 1.80 & 68.65 & 0.824 & 0.49 & 0.90 & 88.55 & 0.885 & \(-\)10.5 \\
**SK+KF** & (autoclave) & 0.47 & 1.07 & 213.1 & 0.938 & 0.47 & 0.61 & 11.90 & 0.911 & \(-\)13.3 \\  & 65 \({}^{\circ}\)C & 0.30 & 0.54 & 202.9 & 0.902 & 0.30 & 0.43 & 15.92 & 0.773 & \(-\)15.4 \\  & 110 \({}^{\circ}\)C & 0.50 & 0.58 & 281.7 & 0.923 & 0.30 & 0.71 & 17.66 & 0.918 & \(-\)14.0 \\  & & & & & & & & & & \\ \hline \end{tabular}
\end{table} 
Table 7: Preparation temperature effect on Pb2+ adsorption on composite adsorbents.