# Novel Polymer Sorbents with Imprinted Task-Specific Ionic Liquids for Metal Removal
## 3 Results and Discussion
### Sorption Studies
#### 3.2.2 Effect of Time  
The time of contact of sorbents and aqueous feed solutions can influence the efficiency of metals removal. In this study, the effect of contact time was studied by making contact with both phases for 1-180 min. The results obtained indicate that, regardless of the structure of the functionalities, the metal sorption is very fast and equilibrium is reached  
Figure 5: Effect of pH on Pb(II), Cd(II), and Zn(II) sorption with sorbent series VBC and VBBr (M(II) = 50 mg/L, pH = 1–6, time–180 min, sorbent dosage—0.1 g, and V—100 mL).  
after 10 min. As shown in Figure 6, the sorption of Zn(II) with VBC-K3.10 is much faster than that observed for other sorbents: 1 min of shaking is enough to achieve equilibrium. In the case of other materials, the results have shown no influence of the functional group structure on the sorption rate.  
To analyze the sorption kinetics, the experimental data were fitted by using the selected models (pseudo-first order, pseudo-second order, intra-particle diffusion, and Elovich models). The fitting results such as kinetic rate constants, correlation coefficients, and qe are presented in Table 3. The results unequivocally show that the pseudo-second-order model describes the kinetics. The coefficient of determination value achieved varied from 0.999 to 1.000, and the calculated values of qe were consistent with the experimental results. These results suggest that the rate-determining step is dominated by chemical sorption. In the case of the VBC-K3.10 sorbent, the values of the reaction rate constant k2 increase from 0.029, and 0.056 to 1.362 g/mg-min for Zn(II), Cd(II), and Cu(II), respectively. In the case of the VBBr-K3.10 sorbent, the values of k2 rise in order Zn(II) \(>\) Cd(II) \(>\) Cu(II) (0.072, 0.056, and 0.029 g/mg-min, respectively)  
\begin{table}
\begin{tabular}{c c c c c c c} \hline \hline \multirow{2}{*}{**Kinetic Model**} & \multicolumn{3}{c}{**VBC-K3.10**} & \multicolumn{3}{c}{**VBBr-K3.10**} \\ \cline{2-7}  & **Cu(II)** & **Cd(II)** & **Zn(II)** & **Cu(II)** & **Cd(II)** & **Zn(II)** \\ \hline qexp (mg/g) & 20.8 & 31.9 & 21.4 & 20.9 & 26.2 & 15.9 \\ \hline \multicolumn{7}{c}{Pseudo-first order} \\ \hline k1(min\({}^{-1}\)) & 0.028 & 0.035 & 0.015 & 0.029 & 0.033 & 0.023 \\ qe.cal (mg/g) & 20.8 & 31.9 & 21.3 & 20.9 & 26.2 & 15.9 \\ R2 & 0.915 & 0.913 & 0.667 & 0.954 & 0.804 & 0.854 \\ \hline \multicolumn{7}{c}{Pseudo-second order} \\ \hline k2 (g/mg min) & 0.056 & 0.029 & 1.362 & 0.032 & 0.056 & 0.072 \\ qe (mg/g) & 20.7 & 32.1 & 21.4 & 20.8 & 26.2 & 15.9 \\ R2 & 0.999 & 0.999 & 1.00 & 0.999 & 0.999 & 0.999 \\ \hline \multicolumn{7}{c}{Intra-particle diffusion} \\ \hline k1(p2\) (mg/g min\({}^{0.5}\)) & 1.18 & 2.12 & 0.99 & 1.37 & 1.61 & 0.95 \\ C & 10.9 & 14.2 & 13.6 & 9.1 & 12.9 & 7.9 \\ R2 & 0.763 & 0.723 & 0.997 & 0.781 & 0.604 & 0.997 \\ \hline \multicolumn{7}{c}{Elovich} \\ \hline \(\alpha\) (mg/g min) & 106.3 & 61.7 & 660.5 & 39.3 & 76.4 & 59.32 \\ \(\beta\) (g/mg) & 0.376 & 0.208 & 0.450 & 0.325 & 0.271 & 0.469 \\ R2 & 0.954 & 0.925 & 0.926 & 0.965 & 0.863 & 0.926 \\ \hline \hline \end{tabular}
\end{table}
Table 3: Kinetic parameters of Cu(II), Cd(II), and Zn(II) sorption with VBC-K3.10 and VBBr-K3.10.  
Figure 6: Effect of shaking time on Cu(II), Cd(II), and Zn(II) sorption with VBC-K3.10 and VBBr-K3.10 (M(II) = 50 mg/L, pH = 5, time: 1–180 min, sorbent dosage—0.1 g, and V—100 mL).