Functional graphene nanocomposite as an electrode for the capacitive removal of FeCl3 from water

Abstract

Capacitive deionization (CDI) is a promising desalination technology which has attracted enormous interest in recent years due to its economic advantages over traditional technologies. In this paper, the facilely synthesized graphene and resol (RGO–RF) nanocomposite was proposed as a CDI electrode for the removal of ferric ions. The addition of resol led to less aggregation of the graphite oxide, while after calcination the structure collapsed and the pore size distribution widened. This was confirmed by Brunauer–Emmett–Teller (BET) techniques. The electrode’s performances, involving the adsorption isotherm and kinetics, were investigated through batch mode experiment. It was found that the electrosorptive capacity of the RGO–RF electrode was 3.47 mg g⁻¹ with an electrical voltage of 2.0 V and initial solution concentration of 40 mg L⁻¹. This is higher than the corresponding activated carbon and graphene electrode due to the presence of resol which is beneficial in restricting the aggregation of graphene, resulting in a high specific surface area and therefore a high electrosorption capacity. Further, the electrosorption of ferric ions onto RGO–RF follows the Langmuir isotherm, implying monolayer adsorption. Meanwhile, regardless of the electrical voltage, the kinetic analysis illustrated that the pseudo-first-order model can describe the electrosorption behaviour of the RGO–RF electrode very well.