Electrochemical deposition of uranium oxide in highly concentrated calcium chloride

Abstract

The coordination circumstances and redox reactions of UO 2 2? in the aqueous solution concentrated by calcium chloride, such as CaCl 2 Á6H 2 O (6.9 M CaCl 2 ), were studied by Raman spectroscopy and electrochemical methods. The frequency of the O=U=O symmetrical stretching vibration suggested that the complex formation of UO 2 2? with Cl -leads to the weakening of U=O bond. In the electrochemical measurements, two-step cathodic currents were observed at -0.090 and -0.4 V (vs. Ag|AgCl) corresponding to the reduction of UO 2 2? to UO 2 ? and that of UO 2 ? to UO 2 , respectively. It was found that UO 2 ? formed at first cathodic current was disproportionated to form UO 2 2? and UO 2 . The UO 2 was identified by X-ray diffraction analysis. Electrolytic deposition of UO 2 was observed in 6.9-4.7 M CaCl 2 and in 14 M LiCl. When small amount of proton, i.e., 0.005 M was coexisted in 6.9 M CaCl 2 , UO 2 2? was reduced to form U 4? instead of UO 2 .

An in-situ X-ray absorption spectroelectrochemical study of the electroreduction of uranium ions in HCl, HNO3, and Na2CO3 solutions

“…To prepare the reduced products, electrochemical bulk electrolysis was combined with UV-Visible spectroscopy or XAFS measurements of UO + 2 [14][15][16][17] and U…”

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

“…The initial scan direction was negative and the hold time at the initial potential was 10 s. In the case of Pt, two cathodic peaks appeared at −0.206 V (I c ) and −0.640 V (II c ) in the negative potential scan, which represents UO 2 2+ reduction to UO 2 + and UO 2 + reduction to UO 2 , respectively (Figure i) . In the reverse scan, a prominent anodic peak at −0.413 V (I a ) is observed which represents UO 2 oxidation to UO 2 + , and an anodic hump of low intensity is observed at around 0 V (II a ) representing UO 2 oxidation to UO 2 2+ . On the other hand, a pair of cathodic (−0.222 V, I c ′) and anodic peak (0.068 V, I a ′) are observed on PEDOT:PSS/Pt in the forward and reverse scan, respectively.…”

Insight into Speciation and Electrochemistry of Uranyl Ions in Deep Eutectic Solvents

“…In the scan of the potential further to negative potential, a peak at around −1.1 V represented further reduction of UO 2 + to UO 2 (Figure S6, Supporting Information). In the reverse scan, a prominent anodic peak at −0.0.9 V is observed, which represented UO 2 oxidation to UO 2 + ; a broad anodic peak at around −0.5 is attributed to the conversion of U­(IV)/U­(VI) directly . The platinum electrode was scanned at various scan rates (0.01–0.2 V/s) in a solution of UO 2 2+ in reline.…”

“…In the reverse scan, a prominent anodic peak at −0.0.9 V is observed, which represented UO 2 oxidation to UO 2 + ; a broad anodic peak at around −0.5 is attributed to the conversion of U(IV)/U(VI) directly. 67 The platinum electrode was scanned at various scan rates (0.01−0.2 V/s) in a solution of UO 2 2+ in reline. When the scan rate was increased from 0.01 to 0.2 V/s, the cathodic and anodic peak positions moved to lower and higher voltages, respectively(Figure 8A), accompanied by the increase of the corresponding peak current densities.…”