In-situ growth of manganese oxide on self-assembled 3D- magnesium hydroxide coated on polyurethane: Catalytic oxidation mechanism and application for Mn(II) removal.

Novel integration of adsorption followed by catalytic oxidation is expected to be more beneficial for higher Mn(II) removal performance. We prepared self-assembled 3D flower-like Mg(OH) coated on granular-sized polyurethane (namely FMHP) via hydrothermal method at 120 °C under a facile synthesis route. The optimized material, FMHP prepared with 7 g MgO and 20 g polyurethane (FMHP), achieved up to 351.2 mg g Mn(II) removal capacity by Langmuir isotherm model. Besides, FMHP exhibited high Mn(II) removal in a wide range of NaCl concentration (0~0.1 M) and pH 2-9. Notably, through consecutive kinetics, BET, XPS, XRD, FESEM, and TEM analyses, it was found that the MnO layer grows in-situ via ion exchange with Mg(II) on FMHP and further boosts the Mn(II) removal via catalytic oxidation during the Mn(II) removal process. Further, column experiments revealed that the FMHP exhibited superior Mn(II) removal capacities up to 135.9 mg g and highly compatible treatment costs ($0.062 m) compared to conventional chemical processes. The granular-sized FMHP prepared by economic precursors and simple synthesis route revealed a high potential for Mn(II) containing water treatment due to its high removal capacities and easy operation.