Removal Of Pb???by Electroadsorption Using GO/MoS₂@ Nickel Foam Electrode

Lead is a kind of heavy metal water pollution,which is toxic and difficult to degrade.It can cause permanent irreversible damage to human kidney,liver,reproductive system and nervous system.Therefore,development of environmental protection and effective treatment of wastewater containing lead is great significance to study.Capacitive deionization?CDI?,a method for removal of heavy metal from aqueous solutions,is one of the promising techniques due to its advantages of efficient,environmentally friendly,no secondary pollution and easy to operate.Electrode materials play a key role in electroadsorption for removal of Pb?II?.In the study,the electrode is prepared by composite of molybdenum disulfide?Mo S₂?and graphene oxide?GO?with nickel foam?NF?,for removal of Pb?II?from wastewater by capacitive deionization.The electrode was characterized by Raman,TEM,XRD and BET.The adsorption mechanism was discussed by XPS,XRD and cyclic voltammetry?CV?.In our processing,Mo S₂nanosheets are growing in well dispersity on GO as the addition of GO prevented the accumulation of Mo S₂.The composite electrode material has a specific surface area of181.63 m²·g^-1,the pore size of 8.86 nm,volume of 0.0036 m³·g^-1,which is very beneficial for Pb?II?adsorption.The experimental Pb?II?removal conditions of GO/Mo S₂electrode CDI were as follows:operation voltage of1.2 V,flow rate of 25 m L·min^-1,p H 5,electrodes distance of 2 mm.At an initial Pb?II?concentration of 2000 mg·L^-1,the GO/Mo S₂electrode adsorption capacity is 4614.9 mg·g^-1,otherwise,GO and Mo S₂electrode adsorption capacity is 1875.9 mg·g^-1and 1175.4mg·g^-1,respectively.When ratio of GO/Mo S₂is 1:3,effect of electoradsorption is the best.Electrode adsorption capacity of Pb?II?increased with voltage across electrode,p H and initial concentration of solution,and decreased with electrode space.Circulating flow rate affected speed of electroadsorption.After electroadsorption,characterization of cathode electrode materials,we found little Pb O₂and Pb O on the electrode.But the CV shows that there is no obvious redox peak in the range 0?1.2 V.It can be explained that the double electrode layer and pseudo-capacitance were simultaneously taking part in process of adsorption,where the double electrode layer was the main one.As results,the adsorption process fitted the pseudo-second-order kinetics model and Langmuir isotherm.The theoretical adsorption capacity of GO/Mo S₂towards Pb?II?is calculated to 7260 mg·g^-1.The GO/Mo S₂electrode present excellent performance in capacitive deionization removal Pb?II?from the aqueous solution.These results will profoundly provide guiding significance for electrochemically GO/Mo S₂and the electrochemical treatment heavy metal wastewater.