Journal: Clean Technologies and Environmental Policy 

Authors: Cho D.-W.; Chon C.-M.; Yang H.; Tsang Y.F.; Song H.

Abstract:

In this study, divalent manganese ions (Mn(II)) were substituted a part of divalent iron ions (Fe(II)) present in Fe oxyhydroxides to prepare novel composites (Mn@Feox). The composites were prepared by (1) simultaneous hydrolysis of Fe(II) and Mn(II), and (2) rapid oxidation with H2O2. The resulting Mn@Feox prepared with different molar ratios of Fe and Mn was characterized and evaluated for their abilities to adsorb arsenic species (As(III) and As(V)) in aqueous solution. X-ray diffraction and field emission transmission electron microscope analyses revealed Mn@Feox has a -(Fe1−x, Mnx)OOH-like structure with their mineralogical properties resembling those of feroxyhyte (-FeOOH). The increase in Mn substitution in Mn@Feox enhanced the oxidative ability to oxidize As(III) to As(V), but it decreased the adsorption capacity for both arsenic species. The optimal Mn/Fe molar ratio that could endow oxidation and magnetic capabilities to the composite without significantly compromising As adsorption capability was determined to be 0.1 (0.1Mn@Feox). The adsorption of As(III) on 0.1Mn@Feox was weakly influenced by pH change while As(V) adsorption showed high dependence on pH, achieving nearly complete removal at pH < 5.7 but gradual decrease at pH > 5.7. The adsorption kinetics and isotherms of As(III) and As(V) showed good conformity to pseudo-second-order kinetics model and Freundlich model, respectively. © 2018, Springer-Verlag GmbH Germany, part of Springer Nature.

Keywords: Adsorption; Arsenic; Iron oxide; Magnetic composite; Manganese; Oxidation

DOI: https://doi.org/10.1007/s10098-018-1528-0