Preparation of manganese sludge strengthened chitosan-alginate hybrid adsorbent and its potential for As(III) removal

Abstract

The manganese sludge from laboratory biological manganese removal filter column backwashing residue was used to modify the Chitosan Alginate Fe-sludge Beads. The Chitosan Alginate Fe-sludge Beads strengthened with manganese sludge (CAFBs) get the oxidation ability and can removal As(III) effectively without a pre-oxidation process. It was characterized by SEM (scanning electron microscopy), XRD (X-ray diffraction), and BET (Brunauer−Emmett−Teller analysis). Batch adsorption experiments were carried out to study the mechanism of As(III) removal. SEM-EDS shows that the surface is rough and rich in iron and manganese element (32.8%). The BET data shows that it is porous and has large surface area (99.20 m2·g−1). XRD proves that the main components of CAFBs are amorphous iron oxide and MnO2.Neutral and weak alkaline conditions (pH = 7–9) were favorable for the adsorption and H2PO4− had obvious inhibitory effect on As(III) removal. The experimental data shows that the Pseudo-second kinetic model, intra-granular diffusion model and Freundlich isotherm can better describe the adsorption process of As(III) by CAFBs. At 298 K, the maximum adsorption capacity of As(III) is 20.16 mg/g. Regeneration studies find that CAFBs can be effectively regenerated by aeration into the NaOH solution.