A comprehensive study on in situ synthesis of a magnetic nanocomposite of magnetite and reduced graphene oxide and its effectiveness at removing arsenic from water

In this study, the in situ synthesis of Fe₃O₄ nanoparticles on the surface of two-dimensional rGO nanosheets was performed. Fe₃O₄/rGO nanocomposites with a different degree of rGO reduction were obtained using various mass ratios between Fe₃O₄ and rGO, and different synthesis times. A comprehensive analysis of the morphology, microstructure, magnetic properties and the reduction degree of the synthesized rGO and Fe₃O₄/rGO nanocomposites was performed. The synthesis conditions were established for the preparation of a Fe₃O₄/rGO nanocomposite with the highest degree of rGO reduction and Fe₃O₄ phase purity. An increase in crystallite size and average particle size with the increase in the Fe₃O₄:rGO mass ratio (from 1:1 to 6:1) was revealed. For the first time, a saturation point for the amount of phase-pure Fe₃O₄ nanoparticles on the rGO surface was determined, as was a specific ratio of magnetite to rGO at which saturation occurred. Examination of the adsorption isotherms and kinetics indicated that the magnetic Fe₃O₄/rGO nanocomposite can serve as an effective adsorbent for arsenic ion (As³⁺) removal from water, with an excellent removal capacity of 14 mg g⁻¹. In addition, the adsorption rate of the Fe₃O₄/rGO nanocomposite enabled 81% As³⁺ uptake within 1 min, which is superior to the literature data.