Capacitive desalination of a low concentration aqueous sodium chloride solution based on a SnO2 and polystyrene co-functionalized graphene oxide electrodes

Abstract

Capacitive desalination for low concentration saline water (NaCl concentration of <60 mg/L) is becoming ever more important and challenging due to its application in special circumstances, such as water purifiers in pacemakers and precision instruments for integrated circuit boards. Here, we develop SnO2 and aminated polystyrene co-functionalized graphene oxide nanocomposites (SnO2/PPAS-rGO) for the effective removal of low concentration NaCl in water. The excellent electrical and hydrophilic properties of SnO2 can effectively reduce the resistivity and improve the wettability of the entire material, making up for the disadvantage of the hydrophobicity of polymer. The introduction of the N atoms of amphiphilic zwitterionic SnO2/PPAS-rGO can improve the adsorption performance as a result of the interfacial interaction between lone-pair electrons and salt ions, and SnO2 can accelerate the charge transmission and furnish sites for activated adsorption. Polystyrene chains with the SnO2 nanoparticles can maintain the exposure of active sites by preventing the aggregation of GO sheets and inhibit the side reaction between the electrode and electrolyte, thereby guaranteeing structural stability with the aid of polytetrafluoroethylene as a binder. After optimizing the synthetic parameters, SnO2/PPAS-rGO-120 presents an ultrahigh electrosorption capacity of 8.07 mg/g at a cell voltage of 1.8 V with a flow rate of 20 mL/min in an aqueous 30.5 mg/L NaCl solution. Most importantly, SnO2/PPAS-rGO-120 shows an excellent adsorption rate (0.0014 s−1), reversibility and regeneration performance during multiple capacitive desalination processes.