A Green Synthesis of Nanocatalysts Based on Reduced Graphene Oxide/Magnetic Nanoparticles for the Degradation of Acid Red 1

The increasing amount of organic dye-polluted wastewater from the textile industry makes the development of techniques for the efficient purification and reuse of wastewater an urgent issue. Accordingly, solid adsorbents based on three-dimensional (3D) reduced graphene oxide (rGO) aerogels combined with magnetic nanoparticles (rGO@Fe3O4) appear to be potential materials, which offer fast and efficient discoloration of dye solutions by dye adsorption, simultaneously acting as Fenton reaction nanocatalysts, and thus may eliminate organic dyes. In this work, 3D rGO@Fe3O4 aerogel nanocatalysts were synthesized via a low-energy, simple, one-step in situ method, in which GO and FeSO4 center dot 7H(2)O were simultaneously reduced. Consequently, monolithic porous nanocatalyst 3D structures were obtained, with a specific surface area of 241 m(2) g(-1) and pore volume 0.39 cm(3) g(-1). The nanocatalysts were applied for the degradation of Acid Red 1 azo-dye in aqueous solution in the presence of hydrogen peroxide, without the need for external energy. The effect of the adsorbent dose, and concentration of dye and peroxide on the dye removal was studied. The degradation of the dye was monitored by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. It was found that an increase in the amount of peroxide allowed complete degradation of the dye together with high molar mass side-products with a conjugated aromatic structure. The good nanocatalyst performance was explained based on the charge-transfer complex established between rGO and the magnetic nanoparticles, allowing the regeneration of ferrous ions during the Fenton process. The authors gratefully acknowledge the financial support by NATO (SfP project G4255), Spanish Government (CTQ2016-80886-R, RTI2018-096294-B-C32 and CTQ2015-73901-JIN), and Basque Government (GV IT999-16 and IT1069-16).