Simultaneous capacitive deionisation and disinfection of saltwater by Ag@C/rGO electrodes

Abstract

Environmental context Deionisation of salt waters is of increasing importance and interest mainly due to the scarcity of fresh water. In a single through pass capacitive deionisation, a relatively high electrosorption efficiency (25%) was observed. Simultaneously, a high disinfection efficiency (97%) was also obtained. This study shows that the new Ag@C/rGO electrodes are feasible for simultaneous deionisation and disinfection of saltwater as a potential source of drinking water. Abstract Capacitive deionisation (CDI) of saltwater, with the advantages of low energy consumption and being environmentally friendly, has been considered a potential solution to the scarcity of fresh water from sea, contaminated or waste waters. In the present work, Ag@C core-shell nanoparticle dispersed rGO (Ag@C/rGO) electrodes were synthesised and used for the CDI of saltwater. To better understand the formation mechanism of the Ag@C core-shell nanoparticles, temperature-programmed carbonisation of the Ag+–β-cyclodextrin complexes was studied by in situ synchrotron small-angle X-ray scattering spectroscopy. At 573 K, the core Ag metal forms Ag@C core-shell nanoparticles with the highest probability nanosizes of 40–80 nm. In the 4-cycle flow-by CDI (once through) experiments using the Ag@C/GO electrodes, high electrosorption efficiencies (25.0–44.9%) were obtained. Each CDI cycle involving electrosorption at 1.2 V and regeneration at 0 V for 1 h was highly reversible. In addition, the disinfection efficiency of the Ag@C/rGO electrodes, contributed by both silver and rGO, was very high (>97%). This study shows that the easily synthesised Ag@C/rGO core-shell carbon-based electrodes are feasible for simultaneous deionisation and disinfection of saltwater as a potential source of drinking water.