Organic Solvent-Free Process for the Rapid Fabrication of Nickel Ferrite-Reduced Graphene Oxide as a Magnetic Nanosorbent Using Supercritical Water

Abstract

In this study, an organic solvent-free process for the rapid fabrication of nickel ferrite anchored on reduced graphene oxide (rGONF) was developed using supercritical water. The rGONF was synthesized from metal nitrates, graphene oxide (GO), and water using a lab-scale batch reactor at 673 K and 30 MPa. The organic solvent was eliminated from the entire process to prevent chemicals from remaining in the as-synthesized magnetic nanosorbents for the sake of future use. Characterization by X-ray powder diffraction, transmission electron microscopy with energy-dispersive X-ray spectroscopy, and Fourier transform infrared spectroscopy has clearly shown the in situ formation of uniform and highly crystalline nickel ferrite nanoparticles on the surface of rGO. Magnetic properties of the as-synthesized rGONF determined using a magnetic property measurement system have shown desirable magnetic features to serve as an adsorbent in practical water-treatment applications. Furthermore, characterization results have implied the completion of the synthetic process within 15 min, extremely faster than the conventional methods. The effects of reaction conditions such as the temperature, reaction time, GO loading, and Ni/Fe molar ratio on anchored NiFe2O4 nanoparticles are also reported herein. The results have suggested that nucleation with a low Ni/Fe molar ratio followed by Ni ion uptake will result in particle growth and crystallization of NiFe2O4 at GO surfaces.

Removal of Cr(III) Ions from Water Using Magnetically Separable Graphene-Oxide-Decorated Nickel Ferrite Nanoparticles

“…The average size of the NiFe 2 O 4 NPs grown over GO in the present work is smaller than the average size of NiFe 2 O 4 NPs grown over GO in the majority of the previously reported works. For example, Sawai et al 38 and Liang et al 39 obtained NiFe 2 O 4 NPs over rGO with mean sizes of 23 and 11 nm, respectively, using a hydrothermal method. Ren et al 40 synthesized CoFe 2 O 4 NPs with a 35 nm average size by a hydrothermal method in the presence of PVP and urea followed by Ar annealing at 550 °C.…”