Enhanced performance of core-shell structured Fe(0)@Fe oxides and Mn(0)@Mn oxides nanocomopsites (ZVIM) towards remediation of arsenic contaminated drinking water

This work presents the synthesis of a hybrid core–shell structured Fe(0)@Fe oxide and Mn(0)@Mn oxide (ZVIM) nanocomposite by an ultrasonically assisted hydrothermal process for decontamination of arsenic in groundwater. Our material possesses a unique core–shell structure with zero-valent Fe and Mn in the core encapsulated by a thin layer of their respective oxides. Herein, the synthesized material utilizes the synergetic effect of Mn-oxide layers of zero-valent manganese (ZVM) to oxidize As(III) to As(V) and iron oxide layers of zero-valent iron (ZVI) for sequestration of total arsenic. The maximum adsorption capacity of ZVIM is calculated to be 58.9 mg g−1 and 101.95 mg g−1 for As(III) and As(V), respectively, which is greater than that of the individual zero-valent manganese and zero-valent iron. The uptake kinetics of both As(III) and As(V) show >80% removal within a reaction time of 20 minutes. The adsorption kinetics follow a pseudo-second order model, suggesting the chemisorption nature of the adsorption process. FTIR and XPS analyses reveal the mechanism of surface interaction of the adsorbent with arsenic species. Furthermore, the effectiveness of our adsorbent is revealed by groundwater tests where the final arsenic concentrations in samples were reduced below the WHO limit for drinking water.