Core-shell structured zero-valent manganese (ZVM): a novel nanoadsorbent for efficient removal of As(iii) and As(v) from drinking water

This work describes the preparation of core-shell structured zero valent manganese (ZVM) for sequestration of total arsenic from drinking water. The material was synthesized using an ultra-sonication assisted hydrothermal route and the prepared material was characterized by using various analytical techniques such as FTIR, XRD, FE-SEM, EDS, AFM, TEM, TGA-DTA, BET and XPS. A combination of data shows successful fabrication of core-shell structured ZVM which consists of core zero-valent manganese (Mn⁰) encapsulated by layers of manganese oxides (Mn₃O₄-MnO₂). XPS analysis provides information regarding the surface interaction of arsenic species with the adsorbent material. The adsorbent was tested for arsenic removal with variation of the solution parameters in a batch technique. Both As(iii) and As(v) could be removed over a wide pH range where the maximum sorption capacity was found to be 30.9 mg g⁻¹ and 72.5 mg g⁻¹ for As(iii) and As(v), respectively. It was observed that the sorption kinetics and adsorption isotherm follow a pseudo second order kinetic model and D-R isotherm model, respectively. The presence of co-anions in a competitive environment had little effect on the arsenic removal properties of the material. Moreover, the exceptional arsenic adsorption capacity of ZVM in ground water and high reusability make it a promising adsorbent material in the removal of total arsenic from aqueous solution.