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

Abstract

Gold nanoparticles / Uranyl / Voltammetry / Impedance spectroscopy / ElectrocatalysisSummary. Gold nanoparticles (AuNPs) were prepared in the matrix of cellulose triacetate (CTA) membrane containing a liquid anion exchanger trioctylmethylammonium chloride (Aliquat-336). The AuCl 4 − ions were transferred in the membrane matrix by anion-exchange process, and then subsequently reduced with NaBH 4 to 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 UO 2 2+ /UO 2 + couple in saturated Na 2 CO 3 solution, using voltammetric techniques. In carbonate solution, the predominant species of UO 2 2+ is [UO 2 (CO 3 ) 3 ] 4− , and a stable UO 2 (CO 3 ) 3 5− complex is formed by one-electron reduction of UO 2 (CO 3 ) 3 4− . Previous reports show that the UO 2 2+ /UO 2 + couple, which is electrochemically reversible in less complexing media, becomes electrochemically irreversible in aqueous CO 3 2− solution. In this study, an electrocatalytic reduction of UO 2 2+ to UO 2 + in saturated Na 2 CO 3 solution 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, k • , 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.

Selective Electrochemical Separation and Recovery of Uranium from Mixture of Uranium(VI) and Lanthanide(III) Ions in Aqueous Medium

“…Next, we dipped PEDOT:PSS/Pt electrode in 10 mM UO 2 2+ in 0.1 M KCl for a few minutes and then the electrode was washed several times with Milli-Q water and CV response was recorded in 0.1 M KCl (Figure a). Reduction and oxidation peaks were observed corresponding to UO 2 2+ /UO 2 redox couple and decayed down to background current after repeated CV cycling showing absorption of UO 2 2+ on the electrode surface . The same experiment was repeated on bare Pt electrode, but no such absorption of UO 2 2+ was observed.…”

Nitric acid concentration strongly influences low level uranium determination on PEDOT-PSS coated glassy carbon electrodes

“…A reduction peak at −0.172 V was observed in each case which signifies uranyl ion adsorption on PEDOT-PSS. 16 But the height of the U(VI) to U(IV) reduction peak current is greater at lower acidity (0.05 M HNO 3 ) which signifies the amount of UO 2 2+ ions adsorption on PEDOT-PSS/GC electrodes increases with a decrease in nitric acid strength. The same experiment was performed with bare GC electrode but no adsorption of UO 2 2+ was observed.…”