# Facile Fabrication of a Low-Cost
## 3 Results and Discussion
### Adsorption Performance of Alg-PAM for Metal Ions  
The adsorption abilities of Alg-PAM for different metal ions (such as Pb\({}^{2+}\), Cu\({}^{2+}\), Cr\({}^{3+}\), Cd\({}^{2+}\), Zn\({}^{2+}\), and Co\({}^{2+}\)) are shown in Table 1. It can be seen from Table 1 that Alg-PAM has a high affinity for Pb\({}^{2+}\), Cu\({}^{2+}\), and Cd\({}^{2+}\), and can remove more than 90% of the corresponding metal ions in the solution, which may be attributed to the carboxyl, hydroxyl, and amino groups on Alg-PAM that bind the metal ions via a coordination effect. In addition, despite the coexistence of Cu\({}^{2+}\), Cr\({}^{3+}\), Cd\({}^{2+}\), Zn\({}^{2+}\), or Co\({}^{2+}\), Alg-PAM can still remove more than 95% of Pb\({}^{2+}\) in the mixed solution, and the relative selectivity coefficients (_k_) are all over 8. This indicates that the prepared Alg-PAM has a higher selectivity for Pb\({}^{2+}\), and can selectively remove Pb\({}^{2+}\) in the presence of other ions.  
In order to confirm the maximum adsorption capacity of the Alg-PAM adsorbent for Pb\({}^{2+}\), we added \(\sim\)100 mg of Alg-PAM to 40 mL of different concentrations of Pb\({}^{2+}\) solution, stirred for 24 hours, filtered, and then measured the amount of Pb\({}^{2+}\) remaining in the filtrate. It can be seen from Figure 7 that as the solution concentration increases, the adsorption capacity of Alg-PAM for Pb\({}^{2+}\) gradually increases. When the Pb\({}^{2+}\) concentration increases from 0.1 to 50 mM, the adsorption capacity of Alg-PAM for Pb\({}^{2+}\) rapidly increases from 8.2 to 252.2 mg/g. However, when the concentration of Pb\({}^{2+}\)  
\begin{table}
\begin{tabular}{c c c c c c c c c} \hline \hline
**Alg-PAM** & **Initial Solution (mM)** & **Removal Efficiency (\%)** & **Adsorption Capacity (mg/g)** & **K\({}_{d}\)** & \(k\)** \\ \hline  & 0.1 (Pb\({}^{2+}\)) & - & 99.2 & - & 8.2 & - & 49.6 & - & - \\  & 0.1 (Cu\({}^{2+}\)) & - & 91.6 & - & 2.3 & - & 4.4 & - & - \\  & 0.1 (Cr\({}^{3+}\)) & - & 92.4 & - & 1.9 & - & 4.9 & - & - \\  & 0.1 (Cd\({}^{2+}\)) & - & 90.2 & - & 4.1 & - & 3.7 & - & - \\ In ultrapure & 0.1 (Zn\({}^{2+}\)) & - & 76.9 & - & 2.0 & - & 1.3 & - & - \\ water & 0.1 (Co\({}^{2+}\)) & - & 69.5 & - & 1.6 & - & 0.9 & - & - \\  & 0.1 (Pb\({}^{2+}\)) & 0.1 (Cu\({}^{2+}\)) & 95.3 & 71.8 & 7.9 & 1.8 & 8.1 & 1.0 & 8.0 \\  & 0.1 (Pb\({}^{2+}\)) & 0.1 (Cr\({}^{2+}\)) & 96.5 & 67.7 & 8.0 & 1.4 & 11.0 & 0.8 & 13.2 \\  & 0.1 (Pb\({}^{2+}\)) & 0.1 (Cd\({}^{2+}\)) & 96.7 & 66.0 & 8.0 & 3.0 & 11.7 & 0.8 & 15.1 \\  & 0.1 (Pb\({}^{2+}\)) & 0.1 (Zn\({}^{2+}\)) & 97.8 & 61.9 & 8.1 & 1.6 & 17.8 & 0.6 & 27.3 \\  & 0.1 (Pb\({}^{2+}\)) & 0.1 (Co\({}^{2+}\)) & 97.1 & 43.2 & 8.0 & 1.0 & 13.4 & 0.3 & 44.0 \\ In lake water & 0.1 (Pb\({}^{2+}\)) & - & 88.4 & - & 7.3 & - & 3.1 & - & - \\ In river water & 0.1 (Pb\({}^{2+}\)) & - & 94.3 & - & 7.8 & - & 6.6 & - & - \\ \hline \hline \end{tabular}
\end{table}
Table 1: Adsorption ability of the sodium alginate-polyacrylamideamide (Alg–PAM) for different metal ions.  
Figure 6: Removal efficiency of Alg–PAM for Pb\({}^{2+}\) at different ambient temperatures.  
exceeds 50 mM, the adsorption capacity of Alg-PAM remains stable and shows no further increase. Therefore, the maximum adsorption capacity of Alg-PAM for Pb\({}^{2+}\) is 252.2 mg/g, which is higher than that of most of the reported Pb\({}^{2+}\) sorbents (Table 2) [28; 29; 40; 41].