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

Abstract

A reduced graphene oxide (RGO) supported Fe₃O₄-MnO₂ nanocomposite (Fe₃O₄-MnO₂@RGO) was successfully prepared for catalytic degradation of oxytetracycline (20 mg/L) by potassium persulfate (PS) and adsorption removal of mixture of Pb²⁺, Cu²⁺, and Cd²⁺ ions (each 0.2 mM) in the synchronous scenario. The removal efficiencies of oxytetracycline, Pb²⁺, Cu²⁺, and Cd²⁺ ions were observed as high as 100%, 99.9%, 99.8%, and 99.8%, respectively, under the conditions of [PS]₀ = 4 mM, pH₀ = 7.0, Fe₃O₄-MnO₂@RGO dosage = 0.8 g/L, reaction time = 90 min. The ternary composite exhibited higher oxytetracycline degradation/mineralization efficiency, greater metal adsorption capacity (Cd²⁺ 104.1 mg/g, Pb²⁺ 206.8 mg/g, Cu²⁺ 70.2 mg/g), and better PS utilization (62.6%) than its unary and binary counterparts including RGO, Fe₃O₄, Fe₃O₄@RGO, and Fe₃O₄-MnO₂. 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 SO₄^•- 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 Fe₃O₄-MnO₂@RGO nanocomposite has a good potential for removing organic-metal co-contaminants in waterbody.

Keywords: Adsorption; Mineralization; Oxytetracycline; Persulfate; Reduced graphene oxide (RGO); Reusability.