Dual-function magnetic reduced graphene oxide nanocomposite: Enhanced caffeine abatement via adsorption and photo-Fenton degradation

Abstract

In this work, an easy method for the preparation of reduced graphene oxide-magnetite nanocomposite was developed via the reduction of graphene oxide by ferrous ions and in-situ synthesis of magnetite nanoparticles on graphene sheets. The resulting magnetic nanocomposite (rGO_m) was tested in the abatement of caffeine, serving as a model for emerging pollutants. The reduction of caffeine concentration was accomplished because of the dual-function of rGO_m both as adsorbent and photo-Fenton catalyst. At pH 3, rGO_m achieved a 99 % degradation of caffeine in 90 min and was able to be reused in 4 consecutive cycles remaining 80 % of degradation capacity. At mild acidic conditions, the combined effect of adsorption and photo-Fenton reaction allows rGO_m to reach an 85 % decrease of initial caffeine concentration in 2 h, under simulated solar light radiation. This abatement capacity is noteworthy for high initial caffeine concentration (30 mg L⁻¹) and simulated solar light compared to similar nanocomposites tested under more favorable conditions, such us, low initial concentration and/or UV-light irradiation. Furthermore, rGO_m serving as adsorbent for caffeine attained a maximum uptake of 56.5 mg g⁻¹ at pH 5 and was able to be reused for 6 consecutive cycles without loss of adsorption capacity. Through its dual function this nanocomposite achieved enhanced adsorption and oxidative degradation of caffeine, making it a competitive option for removing emerging pollutants from wastewater under simulated solar light.