Polyvinyl alcohol-stabilized granular Fe–Mn binary oxide as an effective adsorbent for simultaneous removal of arsenate and arsenite

A novel granular Fe–Mn (GFM) binary oxide sorbent, with a diameter of approximate 2.0 mm and a length of 2.0–3.0 mm, was successfully prepared using extrusion granulation method in this study. The GFM sorbent is highly porous with a BET-specific surface area of 210.3 m²/g. It shows high effectiveness in simultaneously adsorbing As(V) and As(III). The maximal sorption capacities for As(V) and As(III) are 33.2 and 50.7 mg/g at pH 7.0 ± 0.1, respectively, which are superior to most of granular sorbents reported in the literature. The present Ca²⁺, Mg²⁺, humic acids and fulvic acids do not have obvious influence on the arsenic sorption. But, coexisting anions affect negatively arsenic sorption in the following order: H₂PO₄⁻> SiO₃²⁻ > HCO₃⁻ > SO₄²⁻. NaOH solution is an effective eluent for regeneration of the arsenic-loaded GFM. The GFM packed in the fixed-bed column can treat approximately 3400 and 6500 bed volumes of simulated groundwater containing 233 μg/L As(V) and As(III), respectively, before the arsenic concentration in the effluent reached a drinking water limit of 10 μg/L. The features of high effectiveness, selectivity and reusability make the GFM a potential alternative to remove simultaneously As(V) and As(III) from groundwater.