The Synthesis Of Graphene And Carbon Nanotubes Loaded Spinel Metal Oxides For Cr(VI) And MO Removal

Heavy metal ions and organic azo dyes is one of the important pollutants in water, because of their biodegradability and strong toxicity bring a serious threat to plants, animals, and human health. Thus, it is imperative to treat the metal ions and dyes in their wastes to an acceptable level before discharging them into the environmentin order to prevent them cause pollution to the ecological environment. There are many physical, chemical and biological treatment techniques for removing metal ions and dyes from industrial effluent. Among them, adsorption is recognized to be the most popular method because of its low cost, easy operation and high removal efficiency.In this paper, two kinds of different adsorbent materials were prepared and used to remove the heavy metal ions and dyes from the waste water. First, 1,6-hexanediamine-functionalized reduced graphene oxide-zinc ferrite(HDA–RGO–Zn Fe2O4) was synthesized by using a one-step solvothermal process for fast removing Cr(VI). Second, CNT@MCo2O4(M =Ni, Mn, Cu, Zn) nanomaterials were prepared via a simple chemical bath deposition method followed by a post-annealing treatment and used to remove methyl orange(MO).The morphology, crystal structure, element content and types of functional groups, magnetic, valence and pore properties of different nanocomposites were characterized by transmission electron microscope(TEM), scanning electron microscope(SEM), EDX(EDS), X-ray diffraction(XRD), fourier transform infrared spectroscopy(FTIR), Raman, vibrating sample magnetometer(VSM), X-ray photoelectron spectroscopy(XPS) and BET. At the same time, the effects of p H, contact time, different initial concentrations and temperature were systematically researched. In addition, the adsorption kinetics, rate-controlling mechanisms, and thermodynamics of the adsorbents were also comprehensively investigated. The experimental results showed that the adsorption system environment had a great influence on the adsorption process. The low p H value is conducive to the adsorption process for both Cr(VI) and MO. The adsorption kinetic data of the HDA-RGO-Zn Fe2O4 and CNT@MCo2O4(M = Ni, Mn, Cu, Zn) fitted well with the pseudo-second-order kinetic model, and the results of intraparticle diffusion model indicated that overall process appeared to be influenced by intraparticle diffusion and external mass transfer. Moreover, Langmuir and Freundlich isotherms are employed to describe the equilibrium adsorption. The adsorption data of HDA-RGO-Zn Fe2O4 for Cr(VI) were better conformed to the Langmuir model, while the adsorption data of CNT@MCo2O4(M = Ni, Mn, Cu, Zn) for MO closely fitted with both Langmuir model and Freundlich model. Thermodynamic analysis revealed that the adsorption process for both Cr(VI) and MO were spontaneous and endothermic. Furthermore, the adsorption mechanisms of Cr(VI) and MO are also studied in detail.