*3.6. Applicability of the HAMA Hydrogel-Modified Device*

To explore the practical application of the HAMA hydrogel-modified electrochemical device, adsorption experiments were performed in a solution of tap water with 400 μg/L Pb(II). Each device was immersed in the test solution for 20 min, during which the electrochemical accumulation was activated. As shown in Figure 9, all the devices exhibited comparable Pb(II) removal capabilities with an average removal efficiency of 77.2%. The relative standard deviation (RSD) among the eight devices was calculated to be as low as 1.28%, demonstrating good repeatability and reproducibility of the devices. These experimental results reveal that the HAMA hydrogel-functionalized electrochemical device has great potential for deployment at a variety of locations for in situ removal of Pb(II) ions. It is worth mentioning that the water quality conditions (such as pH value, quantity of suspended particulates, other heavy metal ions, etc.) at the locations of interest could affect the adsorption performance of the HAMA hydrogel-modified electrochemical device. Therefore, it is recommended to conduct some preliminary experiments in some specific areas before the large-scale deployment of the devices.

**Figure 9.** Removal efficiency measured for eight HAMA hydrogel-modified electrochemical devices in a solution of tap water with 400 μg/L Pb(II).
