Removal of Tetracycline Pollutants by Adsorption and Magnetic Separation Using Reduced Graphene Oxide Decorated with Alpha-Fe₂O₃ Nanoparticles

Nanocomposites of reduced graphene oxide (RGO) with ferromagnetic alpha-Fe₂O₃ nanoparticles have been prepared in-situ by thermal treatment. The structure and morphology of the hybrid material were studied by X-ray photoelectron spectroscopy, Raman, X-ray diffraction, and transmission electron microscopy. The results show a hybrid material highly modified with alpha-Fe₂O₃ nanoparticles distributed on the graphene surface. The adsorption kinetics show the presence of alpha-Fe₂O₃ nanoparticles on the RGO surface, and the amount of remaining functional groups dominated by ionization and dispersion. The adsorption kinetics of this adsorbent was characterized and found to fit the pseudo-second-order model. The alpha-Fe₂O₃ nanoparticles on RGO modify the electrostatic interaction of RGO layers and tetracycline, and adsorption properties decreased in the hybrid material. Adsorption isotherms fit with the Langmuir model very well, and the maximum capacity adsorption was 44.23 mg/g for RGO and 18.47 mg/g for the hybrid material. Magnetic characterization of the hybrid material shows ferromagnetic behavior due to the nanosize of alpha-Fe₂O₃ with a saturation magnetization, Ms = 7.15 Am/kg, a remanence Mr = 2.29 Am/kg, and a coercive field, Hc = 0.02 T.Rodolfo Cruz-Silva acknowledges the support from the Center of Innovation (COI) Program “Global Aqua Innovation Center for Improving Living Standards andWater-sustainability” from Japan Science and Technology Agency, JST. Authors thank M. Nava for the specific surface area measurements of the materials