Preparation And Properties Of Capacitive Deionized Hydrophilic Electrode

As an unconventional water source,the secondary effluent of municipal sewage treatment plant has good economic and environmental benefits.The unremoved salts need to be treated when reused.Capacitive deionization technology has received extensive attention in recent years due to its advantages of energy saving,high efficiency and no secondary pollution.However,there is a problem of same ion adsorption in the traditional carbon electrode desalination process,which makes the desorption incomplete,and reduces the service life and charge efficiency of the electrode.Membrane capacitive deionization technology,by introducing an ion exchange membrane,shields the common ion effect,improves ion desorption,and overcomes the problems of traditional capacitive deionization.In this thesis,polyvinyl alcohol was used as the matrix and polyelectrolyte was added to prepare the composite hydrogel with ion exchange properties.The main factors affecting its mechanical properties and the structural stability in saline were studied.Using the composite gel as the ion-exchange surface layer,a composite electrode with ion-exchange properties was prepared,and its application effect as a membrane capacitor deionization electrode was studied through electrochemical tests and desalination tests.The results show that the mechanical properties of the composite gel are mainly affected by the amount of cross-linking agent.With the increase of the amount of cross-linking agent,the storage modulus increases,the adjacent strain decreases,and the gel toughness decreases.The addition of polyelectrolyte has no significant effect on the mechanical properties of the composite gel,but has a decisive effect on the ion exchange capacity and salt concentration responsiveness of the gel.With the increase in the amount of polyelectrolyte,the ion exchange capacity of the gel increases,the swelling rate in brine increases,and the equilibrium salt concentration increases.The prepared composite membrane electrode has an obvious double-layer composite structure.The tightly bound gel surface improves the hydrophilicity of the electrode.The addition of polyelectrolyte in the gel layer has no significant effect on the desalination performance and electrochemical performance of the electrode.Electrochemical tests found that the maximum specific capacitance of the electrode was 113.55 F/g,and the specific capacitance of the gel electrode after 50 cycles was 112.73 F/g,with no significant change,indicating that the electrode has a good cycle life.The desalination experiment found that the maximum desalination capacity of the composite electrode was 15.56 mg/g,and the charge efficiency was 64.6%.In summary,the gel-membrane composite electrode effectively shields the common ion effect and Faradaic reaction during desalination,improves the affinity between the membrane and the electrode,and exhibits better desalination effect and cycle stability.The results of this paper provide new ideas and methods for developing membrane capacitive deionization electrodes with good cycling stability and high charge efficiency.