AUTHOR=Zhang Haipeng , Chen Shiyong , Shan Yuhua , Qian Xiaoqing , Yang Yanju , Wang Juanjuan TITLE=Highly Effective Lead Ion Adsorption by Manganese-Dioxide-Supported Core-Shell Structured Magnetite JOURNAL=Frontiers in Environmental Science VOLUME=10 YEAR=2022 URL=https://www.frontiersin.org/journals/environmental-science/articles/10.3389/fenvs.2022.925205 DOI=10.3389/fenvs.2022.925205 ISSN=2296-665X ABSTRACT=

In this research, a magnetic core-shell composite, consisting of a Fe₃O₄ core and a silica shell (called Fe₃O₄@SiO₂), was developed and then functionalized via MnO₂ grafting at different MnO₂ deposition levels (termed Fe₃O₄@SiO₂-MnO₂). The resulting materials were characterized by X-ray fluorescence, X-ray diffraction, a vibration sample magnetometer, transmission electron microscopy, N₂ adsorption-desorption, zeta-potential studies and X-ray photoelectron spectroscopy. Visualizations showed that Fe₃O₄@SiO₂-MnO₂ had a magnetite core with size of 100 nm, overlaid by a rough silica shell and a relatively loose MnO₂ deposition. The Pb(II) adsorption onto the composites was also assessed. It was found that MnO₂ deposition on the Fe₃O₄@SiO₂ surface enhanced Pb(II) adsorption, and the Pb(II) adsorption amount was highly correlated to the MnO₂ deposition level. The adsorption kinetics of Pb(II) followed pseudo-second-order kinetics, and the adsorption rate could be decreased by increasing the initial concentration of Pb(II). A higher pH resulted in enhanced Pb(II) adsorption, which slightly increased with the coexistence of Na⁺ and Ca²⁺, along with the presence of dissolved humic acid. The adsorbent could easily be separated and recovered under the action of the external magnetic component and it displayed stable adsorption behaviour over four adsorption-desorption periods. The results emphasize the high potential of Fe₃O₄@SiO₂-MnO₂ materials for the adsorptive removal of Pb(II) in water.