Valorization of manganese residue to prepare a highly stable and active Fe3O4@SiO2/starch-derived carbon composite for catalytic degradation of dye waste water

To effectively dispose and utilize the manganese residue, a novel manganese residue-based catalyst, mechanical activation-pretreated manganese residue-derived Fe3O4@SiO2/starch-derived carbon composite, was prepared by pre-oxidation of manganese residue and reduction roasting of mechanical activation pretreated manganese residue-starch mixture. In addition, manganese residue-derived Fe3O4@SiO2/starch-derived carbon composite without mechanical activation pretreatment was also prepared for comparative investigation. The prepared composites were used to catalyze H2O2 to generate hydroxyl radicals (·OH) for oxidative degradation of Safranin-T, a well-known synthetic textile dye. It was found that mechanical activation-pretreated manganese residue-derived Fe3O4@SiO2/starch-derived carbon with excellent magnetic performance showed better catalytic activity compared with manganese residue-derived Fe3O4@SiO2/starch-derived carbon composite, with Safranin-T removal efficiency of 99.1% within 20 min under the optimal conditions. The reaction followed a pseudo-first-order kinetic model (R2 > 0.98). The mechanical activation-pretreated manganese residue-derived Fe3O4@SiO2/starch-derived carbon catalyst showed a higher stability with Safranin-T removal efficiency of 97.5% after sixteen cycles. The better stability and activity of mechanical activation-pretreated manganese residue-derived Fe3O4@SiO2/starch-derived carbon catalyst were mainly ascribed to the improved dispersion of manganese residue-derived Fe3O4 onto the SiO2 and starch-derived carbon supports induced by mechanical activation. The inhibiter experiment indicated that the main active species was ·OH on the catalyst surface. Moreover, the possible degradation pathway of Safranin-T was tentatively proposed. [Display omitted] •Manganese residue-based catalyst (MAMR-Fe3O4@SiO2/SC) used for Fenton-like reaction.•Fe2+-Fe3+ and Mn3+-Mn4+ cycles were responsible for the generation of radicals.•Removal efficiency of ST reached 99.1% within 20 min under optimal conditions.•MAMR-Fe3O4@SiO2/SC exhibited excellent stability and activity induced by MA.•Possible degradation mechanism of ST catalyzed by MAMR-Fe3O4@SiO2/SC was proposed.