Synthesis Of Magnetic Graphene Oxide And The Research Of Its Simultaneous Adsorption To Cd(Ⅱ) And As(Ⅴ) From Aqueous Solution

A variety of heavy metal ions often coexist in the aquatic environment, constitute an important source of environmental pollution. Arsenic and cadmium are two of the more common heavy metal ions. Graphene oxide used for adsorption of heavy metal ions showed good performance, but its disadvantage is difficult to separate and recycle.There are some researchers who have set magnetic particle load on the carbon nano material, to synthesize the magnetic carbon nanomaterials which have both high efficient adsorption and easy separation. In this article, Graphene oxide(GO) was synthesized by using the improved Hummer’s method and magnetic graphene oxide(MGO) was prepared by coprecipitation of iron oxide nanoparticles on GO nanosheets. MGO was used as adsorbent for simultaneous removing heavy metal ions Cd(Ⅱ) and As(V) from aqueous solution.MGO was characterized by scanning electron microscopy(SEM), Zeta potentiometer, X-ray powder diffraction(XRD), Fourier infrared spectrum(FTIR) and vibrating sample magnetometer(VSM). Adsorption kinetics, isotherms and the effects of initial pH on adsorption, and Cd(Ⅱ) and As(V) were investigated. In addition, adsorption behavior in Cd(Ⅱ)- As(V) were also investigated.Results showed that GO exhibited layered 2D nanostructure with many wrinkles on the surface. The surface charge was positive at p H<3.5, but was negative at p H>3.5, the pHPZC value of MGO was 3.5. The saturation magnetization of MGO adsorbent was 31.2emu/g, which was sufficient to separate from aqueous solution. The sorption processes coincided with the pseudo-second-order kinetic model and the adsorption equilibrium was reached within 7 h. Adsorption isotherms in mono-component system was accord with Langmuir model, the maximum adsorption capacities for Cd(II) and As(V) were 80.059mg/g、5.857mg/g. In Cd(Ⅱ)-As(V) system, with the increase of As(V) concentration, adsorption of Cd(Ⅱ) have significant increased; with the increase of concentration of Cd(Ⅱ), the As(V) adsorption capacity is also increased, but less significantly than the former.As(Ⅴ) and Cd(Ⅱ) adsorption sequence can significantly affect their adsorption properties of the MGO, In the system of adsorption of earlier As(V) after Cd(Ⅱ), the adsorption capacity of two kinds of targets is close to which is in simultaneous adsorption system; In the system of adsorption of earlier Cd(Ⅱ) after As(V), the adsorption capacity of Cd(Ⅱ) is slightly less reduced than one in simultaneous adsorption system, but is still greater than single adsorption system; And adsorption ratio of As(V) was reduced by 40.8% and 40.8% respectively than simultaneous adsorption system and single system. Results show that apart from the ligand exchange and ion exchange adsorption mechanism, Cd(Ⅱ) and As(V) may form a ternary complex compound on the surface of MGO,which can significantly enhance the adsorption capacity of Cd(Ⅱ) and As(V) on MGO.