Synthesis of magnetite graphene oxide nanocomposite for removal of Congo red from aqueous samples

Graphene is a kind of novel and interesting carbon material that has attracted remarkable attentions from both the experimental and theoretical scientific communities in recent years. In addition to being the principle component of the most carbon based nanomaterials, graphene also exhibits extraordinary properties, such as excellent mechanical, electrical, thermal, optical properties and very high specific surface area [1]. Magnetite graphene oxide (Fe3O4/GO) shows very interesting properties including high stability, large surface area and strong magnetic behavior that make it suitable as a useful adsorbent for simple and rapid separation of chemicals from aqueous solutions [2]. In the present study, graphene oxide (GO) was prepared from graphite according to a modified Hummers’ method by addition of KMNO4 and H2O2 to a solution containing graphite and H2SO4 in the presence of NaNO3 [3]. After that, the synthesized GO was used for preparation of Fe3O4/GO nanocomposite by addition of Fe3+/Fe2+ solution to a 4 M ammonia solution in the presence of GO. The synthesized Fe3O4/GO nanocomposites were characterized by FT-IR, DRS, XRD, SEM and VSM instruments and were used for removal of Congo red dye from aqueous samples. The experimental parameters affecting the removal efficiency were optimized using Taguchi Fractional factorial design method and 100% removal efficiency was obtained at optimum conditions. In order to study the kinetic and isotherm of dye adsorption, pseudo-first-order, pseudo-second-order, intra-particle diffusion and Elovich kinetic models as well as Langmuir, Freundlich and Tempkin isotherm models were studied in optimized conditions. Langmuir isotherm (R2=0.9601 (and pseudo-second-order (R2=0.9959) models were proved to be the best in describing the adsorption isotherm and kinetic, respectively. The reusability experiments show that absorbent has a recycling capability up to twenty times. Finally, the applicability of proposed adsorbent for removal of Congo red from several aqueous real samples was investigated and satisfactory results were obtained. The results showed the synthesized Fe3O4/GO nanocomposite has capabilities such as easy and rapid separation from sample and high potential in removing Congo red, so, it can be introduced as an appropriate adsorbent for removal of this pollutant from water and wastewaters.