The Preparation Of Carbon-based Organic Polymer Composite Membrane Modified Electrode And Its Detection Of Pb²⁺ And Cd²⁺

With the aggravation of human industrial activities,environmental pollution has become a problem that can not be ignored,caused widespread concern in society.Among them,the problem of heavy metal pollution is particularly prominent.Therefore,it is an important issue for environmental researchers to find a rapid method to detect heavy metal ions.The electrochemical heavy metal ion sensor,as a convenient,efficient,sensitive and relatively inexpensive detection tool,has been reported by many scientific researchers.Generally speaking,there are two kinds of methods to prepare modified electrodes:The first is to prepare the modified materials in advance by physical and chemical means,and then to combine the modified materials with the electrodes by coating and immersion;The second is to prepare the modified materials directly on the surface of electrodes by electrochemical deposition or electrochemical polymerization.In the first method,the modified materials and electrodes are often combined by physical methods.If the modified materials are immersed in solution for a long time,the flaking phenomenon often occurs,which affects the detection performance of the sensor.In order to avoid these problems,the second method is used to prepare carbon-based organic polymer composite materials by electrochemical polymerization.The carbon materials here are multi-walled carbon nanotubes?MWCNTs?and graphene oxide?GO?,and the organic polymers are poly?5-amino-2-mercapto-1,3,4-thiadiazole??PAMT?and polypyrrole?PPy?.Combined with the highly sensitive differential pulse stripping voltammetry?DPASV?,the simultaneous detection of Cd²⁺and Pb²⁺was realized.The research contents are as follows:Part one:The MWCNTs/PAMT composite films were fabricated by one-step electropolymerization with cyclic voltammetry.The surface morphology of the composite film was characterized by field emission scanning electron microscopy?FESEM?,and the electrochemical properties were characterized by AC impedance?EIS?and cyclic voltammetry?CV?.In addition,the factors affecting the performance of heavy metals were discussed,including the concentration of MWCNTs,the pH of supporting electrolyte,the preconcentration potential,the preconcentration time,and so on.Finally,two kinds of heavy metal ions were simultaneously detected under the optimal conditions,and the electrode showed a good linear relationship between Cd²⁺and Pb²⁺ions.The detection limit is 0.4?g/L and 0.3?g/L,respectively.Part two:Graphene oxide/polypyrrole?GO/PPy?composites were prepared by potentiostatic one-step electrodeposition.Then the composite membrane was overoxidized by sodium hydroxide to obtain the final modified electrode.Graphene oxide and polypyrrole modified electrodes have almost no current response when detecting Cd²⁺and Pb²⁺.However,the combination of the two combined with the peroxidation process produced a synergistic effect,and the response to the dissolution current of the two target metal ions was significantly enhanced.The morphology of the modified electrode was characterized by FESEM,and the electrochemical characterization was performed by EIS and CV.The modified electrode and detection conditions were optimized by exploring the factors of deposition potential,deposition time,pH of supporting electrolyte,preconcentration potential and preconcentration time.The electrode showed a good linear relationship between Cd²⁺and Pb²⁺ions.The detection limit is 2.165?g/L and 1.425?g/L,respectively.