Preparation Of Graphene-based Composites For Resource Utilization Of Electroplating Heavy Metal Wastewater

Based on the consideration of rapid separation of heavy metals from electroplating wastewater,the magnetic graphene composite modified by polyethyleneimine and Fe₃O₄was synthesized in one step by solvent thermal method?TMGN?.Then,polyaspartic acid was covalently modified at TMGN to form the chelating magnetic graphene composites?TMGA?.The materials were characterized by field emission scanning electron microscopy?SEM?,X-ray diffraction?XRD?and Fourier transform infrared spectroscopy?FT-IR?techniques.A large number of micron-scale spherical Fe₃O₄ particles were uniformly distributed at the graphene,and flocculent polymer was covered at the surface of magnetic graphene.The adsorption of TMGA towards Cr???was investigated in aqueous solution.The pseudo-second-order model seemed to best describe the adsorption kinetics of Cr???,Under the optimal conditions?pH 2.5,45?,310 min?,the maximum adsorption capacity was 165 mg/g with an endothermic and spontaneous process.Based on the consideration of reusing electroplating wastewater for preparing nano electrocatalysts,the magnetic graphene oxide support was prepared by co-precipitation method?CMGO?.Polyethyleneimine and polyaspartic acid were successively coated at CMGO by amide reaction?CMGA?.The present CMGA showed good chelating function and electrical conductivity,which could be used as carrier to prepare binary or ternary layered double hydroxides?Ni/Cr-LDH/CMGA,Zn/Cr-LDH/CMGA and NiZn/Cr-LDH/CMGA?using simulated nickel,zinc and chromium plating wastewater.After calcination,Ni?Zn?/Cr metal oxide/graphene composites could be obtained?Ni/Cr-LDO/CMGA,Zn/Cr-LDO/CMGA and NiZn/Cr-LDO/CMGA?.The present materials were characterized by SEM,XRD,FT-IR and electrochemical techniques.Ni?Zn?/Cr-LDHs were uniformly distributed at the surface of CMGA with layered hydrotalcite structure;three Ni?Zn?/Cr-LDO/CMGA composites displayed aggregated state.The electro-catalysis of above the composites towards oxidation of phenol and water soluble sulfide(S^2-)was investigated,respectively.Among these composites,Ni/Cr-LDO/CMGA showed excellent electro-catalysis with lower oxidation potential and higher peak currentnt.