The influence of F− ion on the electrochemical behavior and coordination properties of uranium in LiCl-KCl molten salt

Chemical Species Transformation during the Dissolution Process of U3O8 and UO3 in the LiCl–KCl–AlCl3 Molten Salt

“…The cyclic voltammetry (CV) technique was employed to study the electrochemical behaviors of U on the W electrode during the U 3 O 8 and UO 3 dissolution process, as displayed in Figure . It is found that the oxidation signal A at 2.36 V is related to the oxidation of UO 2 to UO 2 Cl 4 2– and the redox couple B/B′ is attributed to UO 2 Cl 4 2– /UO 2 Cl 4 3– . , Peaks C and C′ are attributed to the soluble–soluble redox process of UCl 6 2– /UCl 6 3– . − , The cathodic peak D′, at 0.19 V, might be due to the reduction of UCl 6 3– to the U metal, and its corresponding anodic peak D is related to the dissolution of the U metal. , In addition, the peaks E and E′ correspond to the formation/reduction between the U metal and UO 2 …”

“…2− /UCl 6 3− . [4][5][6]26 The cathodic peak D′, at 0.19 V, might be due to the reduction of UCl 6 3− to the U metal, and its corresponding anodic peak D is related to the dissolution of the U metal. 6,36 In addition, the peaks E and E′ correspond to the formation/reduction between the U metal and UO 2 .…”

“…The dissolution process was monitored by inductively coupled plasma-optical emission spectrometry (ICP-OES, Horiba, JY 2000-2). The chemical species were determined as described in our previous work by UV–vis (Hitachi, U-3000, equipped with a 60 integrating sphere accessory), UV–vis–NIR (Agilent, Cary-5000), and solid-state FL (Hitachi, F-4600, excitation with 420 nm). , The electrochemical measurements were performed using an Autolab PGSTAT302N potentiostat/galvanostat controlled with the Nova 1.10 software package from Metrohm. A three-electrode system was also applied for the electrochemical measurements.…”

“…In this work, the dissolution behavior of U 3 O 8 in the LiCl–KCl molten salt with the assistance of AlCl 3 was studied, and the chemical species’ transformation of uranium during the dissolution process was also explored. Electrochemical methods, as well as ultraviolet–visible absorption spectroscopy (UV–vis), fluorescence emission spectroscopy (FL), and X-ray absorption fine structure (XAFS, including XANES and EXAFS) spectra are useful methods for determining the oxidation state and local coordination environment of dissolved products in the molten salt. − To understand the dissolution mechanism of high-valence uranium oxide more clearly, the dissolution process of UO 3 was also studied for comparison. Meanwhile, in the absence of LiCl–KCl, the reaction products of U 3 O 8 or UO 3 with AlCl 3 were analyzed by X-ray diffraction (XRD) to further determine the influence of AlCl 3 .…”

The Coordination Chemistry of f‐Block Elements in Molten Salts

“…[39] Different from Am(III), U(III) can interact with only one F À ion to form UCl 5 F 3À complex ions, as is shown in our recent study using XAS and MD simulation methods. [40] For tetravalent Ans, the Delpech and our groups explored the solution structures of Th(IV) and U(IV) in LiClÀ KClÀ LiF melts respectively and suggested that at most three F À ions can enter the first coordination sphere of An(IV). [40][41] In addition, temperature also has a weak and irregular impact on the coordination behavior of Ans in molten salts.…”