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

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 m·g). XRD proves that the main components of CAFBs are amorphous iron oxide and MnO.Neutral and weak alkaline conditions (pH = 7-9) were favorable for the adsorption and HPO 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.