Electrochemical studies of U(VI)/U(V) in saturated Na2CO3solution at gold nanoparticles embedded CTA-modified electrode

Abstract

AbstractGold nanoparticles (AuNPs) were prepared in the matrix of cellulose triacetate (CTA) membrane containing a liquid anion exchanger trioctylmethylammonium chloride (Aliquat-336). The AuCl4−ions were transferred in the membrane matrix by anion-exchange process, and then subsequently reduced with NaBH4to form AuNPs in the membrane. The AuNPs-embedded CTA (AuNPs-CTA) membrane was characterized by UV-visible spectroscopy, XRD and AFM. The electrochemical properties of AuNPs-CTA modified electrode were evaluated by studying redox behavior of UO22+/UO2+couple in saturated Na2CO3solution, using voltammetric techniques. In carbonate solution, the predominant species of UO22+is [UO2(CO3)3]4−, and a stable UO2(CO3)35−complex is formed by one-electron reduction of UO2(CO3)34−. Previous reports show that the UO22+/UO2+couple, which is electrochemically reversible in less complexing media, becomes electrochemically irreversible in aqueous CO32−solution. In this study, an electrocatalytic reduction of UO22+to UO2+in saturated Na2CO3solution was observed at AuNPs-CTA-modified electrode with higher current density and faster heterogeneous electron-transfer kinetics than that at bare Au electrode. The standard heterogeneous rate constant,kº, for the reduction process at AuNPs-CTA modified electrode was about 25 times higher than that of bare Au electrode. Therefore, it is concluded that AuNPs-CTA membrane has improved the interfacial electron-transfer properties of electrode, resulting in a better electrochemical response than bare Au electrode.