Adsorption and heterogeneous Fenton catalytic performance for magnetic Fe3O4/reduced graphene oxide aerogel

Heterogeneous Fenton system has been widely used in water treatment because of its effective degradability in a wide range of pH. A two-step hydrothermal method for the synthesis of Fe3O4/reduced graphene oxide (RGO) aerogel was designed as an efficient and recyclable heterogeneous Fenton catalyst for degradation of methylene blue (MB). Firstly, the Fe3O4 colloidal solution was synthesized by hydrothermal progress. Secondly, graphene oxide hydrogels were formed by the self-assembling and reduced to graphene during the hydrothermal reaction. Meanwhile, zero-dimensional Fe3O4 nanoparticles were anchored onto the graphene oxide through the colloidal coagulation effect. The obtained samples were characterized by XRD, SEM, TEM, BET, Zeta, XPS, Raman, TG, and VSM. Adsorption isotherm and kinetics of MB onto Fe3O4/RGO composites revealed that the maximum adsorption capacity was 163.83 mg/g, and the adsorption process confirmed to the pseudo-second-order model. The determinants of heterogeneous Fenton system including oxidant concentration, initial pH, and reaction mechanism were investigated. The studies indicated that MB degradation efficiencies increased with the initial pH increasing (pH 3–10), showing a complete degradation in alkaline condition within 60 min. It is due to that catalytic reaction mainly occurs on the solid–liquid interface, as pH values increase, the electrostatic attraction between the cationic MB molecules and the surface of Fe3O4/RGO increases, the enhancement of adsorptivity is helpful to improve catalytic activity. The catalyst can be easily recovered by an applied magnetic field and exhibited excellent stability after five degradation cycles.