Nanoparticles of magnetite anchored onto few-layer graphene: A highly efficient Fenton-like nanocomposite catalyst

Developing a catalyst with high efficiency and recyclability is an important issue for the heterogeneous Fenton-like systems. In this study, magnetic Fe₃O₄ and reduced graphene oxide (RGO) nanocomposites were prepared by a facile alkaline-thermal precipitation method and employed as a highly effective heterogeneous Fenton-like catalyst for methyl orange (MO) degradation. Characterization of these nanocomposites by XRD, FTIR, Raman, FESEM and TEM revealed that nanoparticles (NPs) of Fe₃O₄ were tightly anchored on the few-layer RGO sheets. The anchoring of Fe₃O₄ NPs and the reduction of GO were achieved in one pot without adding any other reducing agents. Based on the measurements of GO surface Zeta potentials, a possible anchoring mechanism of Fe₃O₄ NPs onto RGO sheets was given. The Fe₃O₄/RGO nanocomposites exhibited much higher Fenton-like catalytic efficiency for MO degradation than pure Fe₃O₄ NPs. This degradation process followed the first-order kinetics model, where k₁ and T complied with the Arrhenius equation with E_a of 12.79 kJ/mol and A of 8.20 s^-1. Magnetic measurements revealed that Fe₃O₄/RGO nanocomposites were ferromagnetic as indicated by the presence of magnetic hysteresis loops. The Fe₃O₄/RGO nanocomposites showed good stability and recyclability. Hydroxyl radicals, OH were determined as the dominant oxidative species in Fe₃O₄/RGO-H₂O₂ system and the Fenton-like mechanism for MO degradation in water was proposed and discussed.