Evaluation of Fe3O4-MnO2@RGO magnetic nanocomposite as an effective persulfate activator and metal adsorbent in aqueous solution

A reduced graphene oxide (RGO) supported Fe 3 O 4 -MnO 2 nanocomposite (Fe 3 O 4 -MnO 2 @RGO) was successfully prepared for catalytic degradation of oxytetracycline (20 mg/L) by potassium persulfate (PS) and adsorption removal of mixture of Pb 2+ , Cu 2+ , and Cd 2+ ions (each 0.2 mM) in the synchronous scenario. The removal efficiencies of oxytetracycline, Pb 2+ , Cu 2+ , and Cd 2+ ions were observed as high as 100%, 99.9%, 99.8%, and 99.8%, respectively, under the conditions of [PS] 0 = 4 mM, pH 0 = 7.0, Fe 3 O 4 -MnO 2 @RGO dosage = 0.8 g/L, reaction time = 90 min. The ternary composite exhibited higher oxytetracycline degradation/mineralization efficiency, greater metal adsorption capacity (Cd 2+ 104.1 mg/g, Pb 2+ 206.8 mg/g, Cu 2+ 70.2 mg/g), and better PS utilization (62.6%) than its unary and binary counterparts including RGO, Fe 3 O 4 , Fe 3 O 4 @RGO, and Fe 3 O 4 -MnO 2 . More importantly, the ternary composite had good magnetic recoverability and excellent reusability. Notably, Fe, Mn, and RGO could play a synergistic role in the improvement of pollutant removal. Quenching results indicate that surface bounded SO 4 •– was the major contributor to oxytetracycline decomposition, and the -OH groups on the composite surface shouldered a significant role in PS activation. The results indicate that the magnetic Fe 3 O 4 -MnO 2 @RGO nanocomposite has a good potential for removing organic-metal co-contaminants in waterbody. Graphical Abstract