Preparation Of Functionalized Graphene Oxide And Its Adsorption Properties For Copper(Ⅱ),Lead(Ⅱ) And Cadmium(Ⅱ)

With the rapid development of industry and agriculture,heavy metal pollution in water has become a serious environmental pollution problem.Common metal elements like Cu,Pb and Cd have been widely used in electroplating,metallurgy,battery,pigments and other fields.A lot of wastewater containing Cu(II),Pb(II)and Cd(II)heavy metal ions were produced in the process of production.If effective measures are not taken to deal with these heavy metal ions,it will pose a serious threat to the ecological environment and human health.The adsorption method is regarded as one of the the most promising methods of heavy metal wastewater treatment with its simple operation and high processing efficiency.However,the traditional adsorbents have the problems of low adsorption capacity,difficult recovery,narrow range of pH value and poor adsorption and desorption performance.Therefore,it is urgent to develop adsorbent materials with excellent adsorption performance to make up for the shortcomings of traditional adsorbents.In this study,graphene oxide(GO)was prepared by modified Hummers method.Fe3O4 magnetic particles were grafted onto GO surface by chemical co-precipitation method to prepare magnetic graphene oxide(MGO),and then diethylenetriaminepentaacetic acid(DTPA)was used as the modifier to functionalize MGO via diethylenetriamine through an amidation reaction.A new adsorbent DTPA/MGO composites material was obtained.The surface morphology,functional groups and elemental composition of the prepared DTPA/MGO composites were characterized by using scanning electron microscopy(SEM),X-ray diffraction(XRD),infrared spectrometer(FT-IR),X-ray spectrometer(XPS)and Zeta potential.The results showed that DTPA was grafted successfully to MGO surface.The effects of initial pH value,concentration of heavy metal ions,adsorption time,reaction temperature and ionic strength on the adsorption properties of DTPA/MGO composites were investigated.The experimental results indicated that the DTPA/MGO composites show good adsorption properties for Cu(II),Pb(II)and Cd(II)ions at the pH value of 3-6.The adsorption processes fits well with the Langmuir adsorption isotherm and the pseudo-second-order model.The maximum adsorption capacities for Cu(II),Pb(II)and Cd(II)ions at pH 3.0 were 131.4 1,387.60 and 286.53 mg/g,respectively.The thermodynamic studies demonstrated that adsorption processes were endothermic and spontaneous.Moreover,the DTPA/MGO composites could selectively adsorb Pb(II)ions from multi-metal mixed systems.Adsorption and desorption results showed that the DTPA/MGO composites have excellent reusability.Through analyzing the characterization of DTP A/M GO composites before and after adsorption,the mechanism of adsorption of Cu(II),Pb(II)and Cd(II)heavy metal ions on DTPA/MGO composites was investigated.The results showed that the adsorption mechanism of DTPA/MGO composites is the ion exchange,electrostatic adsorption and surface complexation reactions between functional groups and metal ions on the surface of adsorbent.These results suggested that DTPA/MGO composites have great potential in the treatment of acidic heavy metal wastewater,especially for the wastewater containing Pb(Ⅱ).