Preparation Of Modified Activated Carbon-based Flow Electrode And The Study On Their Desalination Performance In Capacitive Deionization

With the advantage of simple operation and high desalination efficiency,the flow electrode capacitive deionization(FCDI)has attracted much attention in recent years and become a new type of water treatment desalination technology.In this paper,two kinds of activated carbon(AC)materials with charged functionalization method were prepared and the effects of the types of surfactant,the mass ratio of active materials to surfactants on the dispersion,stability and electrochemical properties of the flow electrode were studied.And the desalination performance of the flow electrode under the optimum preparation conditions was also investigated.The functional modification of AC was carried out by chemical oxidation method and amination treatment methods respectively and the corresponding modified materials are named as AC-O and AC-N.The effects of surfactant types(sodium dodecyl sulfate SDS and cetyltrimethylammonium bromide CTAB)and content on the performance of flow electrodes were investigated.The results show that the Zeta potential of the AC-O flow electrode with SDS as the surfactant is-34.8 m V,which is much lower than that of AC-O flow electrode with CTAB as the surfactant(21.3 m V),indicating that the surfactant SDS displays better dispersion property for the AC-O flow electrode than that of CTAB.And the specific capacitance of the AC-O flow electrode with SDS as a surfactant is 16.4 F/g.The Zeta potential of the AC-N flow electrode with CTAB as surfactant(22.4 m V)is higher than that of the AC-N flow electrode with SDS as surfactant(-1.75 m V),indicating that the dispersion performance of CTAB as the surfactant for the AC-N flow electrode is better than that of SDS.And the specific capacitance of the AC-N flow electrode with CTAB as a surfactant is 11.2 F/g.In order to further improve the flow performance of AC-N,the content of CTAB in AC-N flow electrode was optimized.The results show that when the content ratio of AC-N and CTAB is 7:1,the Zeta potential and specific capacitance of AC-N flow electrode are 23.5 m V and 13.6 F/g respectively,which indicates that the suspension stability of flow electrode is the best at this ratio.The two modified flow electrodes under the optimized condition were configured with the symmetrical and asymmetric cells and FCDI desalination experiments were carried out.Among them,the symmetric FCDI cells are AC-O/SDS-AC-O/SDS and AC-N/CTAB-AC-N/CTAB,and the asymmetric FCDI cell is AC-O/SDS-AC-N/CTAB.The results of the saturated adsorption test show that all the three FCDI cells exhibit the same adsorption trend.The desalination efficiency and mean electrosorption rate of the symmetric FCDI cell AC-O/SDS-AC-O/SDS are 5.24%and 0.688 mg/(g.min^-1)respectively and the corresponding values of the symmetric FCDI cell AC-N/CTAB-AC-N/CTAB are 5%and 0.598 mg/(g.min^-1)respectively.And the desalination efficiency and mean electrosorption rate values of the asymmetric FCDI cell AC-O/SDS-AC-N/CTAB are 6.84%and 0.955 mg/(g.min^-1).The above results indicate that the desalination performance of the asymmetric FCDI cell is better than that of the symmetric FCDI cells.