Synthesis and characterization of magnetically separable and recyclable crumbled MgFe2O4/reduced graphene oxide nanoparticles for removal of methylene blue dye from aqueous solutions

Graphene oxide (GO) is an excellently conductive carbon material composed of versatile building blocks that can self-assemble a broad range of nanoparticles, and the features of GO can be tuned to accommodate various self-assembly approaches. Using the benefits of a simple self-assembly of two oppositely charged nanomaterials via electrostatic interactions, GO and MgFe2O4 can be self-assembled together, and the assembled composites are expected to possess special properties as catalysts in comparison to their individual counterparts. In this research, novel magnetic separable MgFe2O4/crumbled reduced GO (rGO) nanoparticles of surface area 35 m(2)/g and adsorption capacity 24.81 mg/g were synthesized to eliminate methylene blue (MB) dye as a primary cationic organic dye pollutant model. The physicochemical features were explored using field emission scanning electron microscopy, high resolution transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, and N-2-adsorption/desorption isotherms. The rod-like structured of the as-synthesized nanoparticles with crystallite size of 11 nm were deposited homogeneously on the surface of wrinkles of rGO with a crumbled sheet structure. The microstructure analysis indicated the accumulation of MgFe2O4 on the wrinkles and the edges, rather than the basal planes, due to the distribution of the COOH groups on the GO. The influences of catalyst dose, dye concentration, pH, rate of agitation, and the change in temperature during the dye removal process were investigated. The elimination of MB followed a pseudo second-order reaction and was characterized by multi-layer formation on the solid surface. The values of enthalpy and entropy change were 61 and 0.219 kJ/ mol, respectively, indicating a strong interaction between dye molecules and solid surface and the enhancement of the random arrangement of dye molecules on the adsorbent surface. The novel magnetic and easily separable nanoparticles retained 75% of their reactivity on dye removal after four consecutive cycles. The prepared magnetic rGO will allow the synthesis of highly effective and low-cost nanoparticles for dye removal from aqueous solution.