Asymmetric polysaccharide-bound graphene electrode configuration with enhanced electrosorption performance for uranium (VI) ions

Abstract

As an energy-saving and facile technology, the potential of capacitive deionization (CDI) starts to surface in enrichment and recovery of uranium (U(VI)) from aqueous solutions. However, co-ion expulsion effect and poor surface wettability of electrode materials limit the eletrosorption performance. Here, polysaccharides xanthan gum (XG)- and chitosan (CS) -bound porous reduced graphene (RGH) electrodes were rationally designed, and then assembled into asymmetrical electrode configuration for U(VI) eletrosorption. Owing to the introduction of polysaccharide binders, the oppositely charged groups on the surface of cathode and anode weaken the co-ions exclusion effect as well as endow their superior surface hydrophilicity and electroconductivity, which facilitates the electrosorption for U(VI). Meanwhile, the negatively charged carboxylate groups could act as extra micro electric fields to attract U(VI) cations, and form stronge complexation between them. As a consequence, asymmetrical polysaccharide-bound RGH configuration gave rise to a larger removal ratio of 97.9% within 4 h at 1.2 V, as well as 2.5 times faster kinetics than symmetrical PVDF-bound RGH electrode configuration. Moreover, the accumulated adsorption capacity in six adsorption–desorption cycles of the former is up to 1413.0 mg g−1, 75% higher than the latter, which is of practical significance and economic benefit for electrosorption application.