Selective single-atom adsorption for precision separation of lead ions in tap water via capacitive deionization
Zhenwei Gao, Luqing Wang, Xingkang Huang, Chris J. Benmore, Hongting Pu, Jianguo Wen, Wen Zhuang, Maria K. Y. Chan, Junhong Chen
Abstract
• Pb 2+ removal by various functional groups as CDI electrode materials was studied. • GO-COOH exhibited superior Pb 2+ removal efficiency compared to -SH and -NH 2 . • GO-COOH displayed the highest Pb 2+ removal selectivity over Ca 2+ and Mg 2+ . • Pb 2+ exhibited a theoretically stronger affinity to -COOH than to -SH and -NH 2 . Capacitive deionization (CDI) offers a cost-effective and low-energy method for selective removal of Pb 2+ from drinking water. Modifying CDI electrode surfaces with functional groups presents a versatile approach to enhancing selective ion adsorption capacity. However, a comprehensive understanding of the selectivity and removal efficiency of Pb 2+ among diverse functional groups remains unexplored. Here, we investigated the effects of different functional groups (-SH, -COOH, and -NH 2 ) attached to the graphene oxide (GO) electrode surfaces on Pb 2+ selectivity and removal efficiency. Surprisingly, GO-COOH demonstrated single-atom adsorption of Pb 2+ , displaying superior removal efficiency and selectivity compared with -SH and -NH 2 , although -SH possesses significant chelation capability for Pb 2+ . Both density functional theory (DFT) calculations and X-ray pair distribution function (PDF) analyses confirmed that Pb 2+ exhibits a theoretically higher affinity to -COOH. This research deepens our understanding of the interactions between functional groups and heavy metal ions, enabling selective and rapid separation of target cations for water purification.