Mechanisms of Synergistic Removal of Low Concentration As(V) by nZVI@Mg(OH)₂ Nanocomposite

In this work, by using Mg­(OH)₂ nanoplatelets as support material for nanoscale zerovalent iron (nZVI), nZVI@Mg­(OH)₂ composite was prepared and found to have super high adsorption ability toward As­(V) at environmentally relevant concentrations. It was revealed that the variation of corrosion products of nZVI in the presence of Mg­(OH)₂ and Mg²⁺ is an important factor for increase in the adsorption ability toward As­(V). X-ray diffraction (XRD) analysis indicated that the weakly basic condition induced by Mg­(OH)₂ decreases the lepidocrocite (γ-FeOOH) and increases the magnetite/maghemite (Fe₃O₄/γ-Fe₂O₃) content in the corrosion products of nZVI, and the latter has better adsorption affinity to As­(V). Moreover, extended X-ray absorption fine structure spectroscopy (EXAFS) indicated that the coordination between arsenic and iron minerals is influenced by dissolved Mg²⁺, leading to probable formation of magnesium ferrite (MgFe₂O₄) which has considerable adsorption affinity to As­(V). This work provides an important reference not only for the design of pollution control materials but also for understanding arsenic immobilization in natural environments with ubiquitous Mg²⁺ ion