Synergy of Mn-Fe-Al and reconstruction of chemisorption & physisorption in arsenic removal

Arsenic contaminations have caused adverse effects on the water environment. In this work, oxidation and adsorption of arsenic proceeded on the surface of nanostructured MnO2/β-FeOOH loaded γ-alumina (MFA) to control the contaminations. The synergy of Mn-Fe-Al and adsorption mechanism were illustrated distinctly by the preparation of new morphological MnO2 and the unique core–shell structure of MFA. The arsenite was transformed into arsenate by tussocky MnO2, the arsenate was adsorbed chemically and physically by β-FeOOH or alumina after the vanishment of the upper MnO2. In acidic conditions, approximately 88 % of arsenic removal efficiency was achieved. The adsorption kinetics followed pseudo-second-order model, the isotherm fitted better with Freundlich isotherm model. The chemisorption of H2AsO4− on alumina/β-FeOOH were conducted by covalent/ionic bonds, respectively, which were deduced by the density functional theory (DFT) calculations. The physisorption of arsenic was dominated by hydrogen bonds and van der Waals interactions inferred from DFT and reduced density gradient (RDG) analysis. The preparation of adsorbents and the insight into adsorption by experiments and theoretical calculations will subserve the purification of the water environment.