Synthesis Of Magnetic Graphene Oxide Adsorbent For Cd(Ⅱ) And Ionic Dyes Removal From Aqueous Solution

Heavy metal and ionic dyes always coexistence and constitute the most importantand dangerous source of environmental pollution. Graphene oxide has the potential inthe application to remove heavy metal ions and ionic dyes in wastewater, but it suffersfrom separation inconvenience. If the carbon nano-materials was given themagnetism to form magnetic carbon nanomaterials, which not only has high adsorptioncapacity but also easy separation properties of magnetic materials.In this paper,Graphene oxide (GO) was synthesized using Hummer’s method and magneticgraphene oxide (MGO) was prepared by coprecipitation of iron oxide nanoparticles onGO nanosheets. MGO was used as adsorbent for simultaneous removing heavy metalions Cd(Ⅱ) and anionic dye including methylene blue (MB),organg G (OG) andcongo red from aqueous solution.Graphene oxide was characterized by scanning electron microscope(SEM),transmission electron microscope(TEM)， zeta SIZER, X-ray powder diffraction(XRD), Fourier Transform Infrared Spectroscopy(FTIR) and vibrating samplemagnetometer(VSM). Adsorption kinetics, isotherms and the effects of initial pH onadsorption, and Cd(Ⅱ) and anionic dye removal efficiency in tap water wereinvestigated. In addition, adsorption behavior in Cd(Ⅱ)-MB, Cd(Ⅱ)-OG andCd(Ⅱ)-CR binary system and recycle of MGO were also investigated.Results showed that GO exhibited layered2D nanostructure with many wrinkleson the surface. The surface charge was positive at pH＜3.5, but was negative at pH＞3.5, the pHPZCvalue of MGO was3.5. The saturation magnetization of MGOadsorbent was31.2emu/g, which was sufficient to separate from aqueous solution.The sorption processes coincided with the pseudo-second-order kinetic model and theadsorption equilibrium was reached within7h. Adsorption isotherms inmono-component system was accord with Langmuir model, the maximum adsorptioncapacities in ultrapure water for Cd(II), MB, OG and CR were160.87mg/g、64.23mg/g、20.38mg/g and143.62mg/g respectively. The adsorption capacity suppressedfor Cd(II) with increasing MB concentration and almost was not affected for MBwith increasing Cd(II) concentration in Cd(Ⅱ)-MB binary system. However, theadsorption capacity enhanced for OG and CR with increasing Cd(II) concentration andfor Cd(II) was independent on the concentration of OG and CR in Cd(Ⅱ)-OG andCd(Ⅱ)-CR binary system.Tthe maximum adsorption capacities in tap water for Cd(II),MB, OG and CR were59.69mg/g,55.81mg/g,20.32mg/g and287.57mg/g respectively, which was37.1%,86.89%、99.80%and200.23%of that in ultrapurewater, indicating that MGO was effective in removing ionic dyes and had the potentialin the application of ionic dyes removal in real wastewater treatment. Tthe adsorptioncapacities of Cd(II), MB, OG and CR on MGO was28.63mg/g、25.15mg/g、11.88mg/g and72.27mg/g after ternary cycle，which was33.77%、42.25%、47.32%and82.95%that of the first adsorption, indicating that MGO has a good reproducibility andwas suitable to use for recycling.