Study on Electrosorption of As Ions in Aqueous Solution by Modified Graphene

In this paper, the modified graphene material, graphene/titanium dioxide (GA/TiO₂) composite, was prepared by hydrothermal method. The morphology, pore structure and electrochemical properties of graphene (GA) and GA/TiO₂ were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), nitrogen adsorption-desorption, Raman spectroscopy and electrochemistry. Then GA and GA/TiO₂ were assembled into electrodes to remove As ions by capacitive deionization (CDI) method. The removal efficiency of As ions was analyzed through different experimental conditions including voltage, circulating flow rate, temperature and initial As ion concentration. The results show that GA/TiO₂ had a three-dimensional porous structure with specific surface area of 416.99 m²·g^-1 and specific capacitance of 320.75 F·g^-1, which were better than that of GA. In addition, the removal performance of As ions by CDI on GA/TiO₂ electrode was better than that of GA electrode. The removal efficiency and adsorption capacity of As ions increased with the increase in voltage, but decreased with the increase in temperature. However, the removal efficiency decreased and adsorption capacity increased with the increase in initial ion concentration. The circulating flow rate had no significant effect on the removal efficiency. Moreover, the adsorption process of As ions on GA/TiO₂ electrode can be well fitted by the pseudo-first order kinetic model and Freundlich model.