An Efficient System for Uranyl Electrodeposition and Investigation of the Uranyl Electrochemical Behavior

Abstract

The redox mechanism of U(VI) to U(IV) in carbonate system was studied by cyclic voltammetry. Based on the analysis of cyclic voltammograms at different pHs and switching potentials, combined with the speciation analysis of uranyl at different pHs, the two-step reactions of U(VI) to U(V) and U(V) to U(IV) were confirmed at pH 8.0. The determination results of U(Ⅴ) diffusion coefficient and U(Ⅴ) to U(IV) reaction kinetic rate constant under different pHs showed that pH 8.0 has certain advantages over other pHs. The calculated results of these two parameters at different temperatures revealed that the increase of temperature promotes the diffusion coefficient of U(V) and the kinetic rate constants of U(V) to U(IV) reaction. The SEM and EDS analysis of the electrodeposited samples showed that uranyl can be rapidly, stably, and uniformly deposited on the Pt electrode surface by potentiostatic deposition in carbonate system. The XRD results confirmed the complexity of the deposited samples under different pHs, not just the UO2. The fitting results of XPS spectra under different potentials proved that the deposition samples contained uranium-containing oxides, uranium-containing carbonates, and uranium-containing hydroxides. In addition, the deposition mechanism of the potentiostatic deposition in different potential intervals has been established.