Electrochemistry of Uranium (IV) in Acidic AlCl3 ‐ NaCl Melts at 175°C

Abstract

Solutions of uranium (IV) in acidic AlCl3‐normalNaCl melts false(52–70 normalmole percent AlCl3false) at 175°C were prepared by dissolving uranium (IV) oxide or chloride. The electrochemistry of uranium (IV) in these melts, investigated by pulse polarography and cyclic voltammetry, corresponds to two reversible one‐electron reactions. For the U(IV)/U(III) redox couple, the reaction is given byUClx)(4−x++e−→U3++xCl−where 3≥x≥1 , the lower values of x being found for the most acidic melts. Thus, uranium (IV) exists in solution as UCl3+ , UCl22+ , and UCl3+ . For the U(V)/U(IV) redox couple, the reaction is written asUCly)(5−y++e−→UClx)(4−x++)(y−xCl−where false(y−xfalse)=3 over almost the entire pCl range covered in this work. Therefore, the uranium (V) species in solution are formulated as UCl6− , UCl5 , and UCl4+ . However, since some oxide impurities are probably always present in molten chloroaluminates, the existence of a UOClyfalse(3−yfalse)+ species cannot be totally excluded.

Electrochemical and spectroscopic studies of neptunium in the aluminum chloride-1-n-butylpyridinium chloride melt at 40.degree.C

“…C. Extrapolation from Nugent's Potentials Linearization Theory. Nugent has proposed29 that the standard oxidation potentials E°' of the III-II and IV-III redox systems of lanthanides and actinides in the same aqueous solvent are related to q, the number of f electrons in the oxidized form, following the equation E°= IV'+ (E-A')q-F(q) (13) The values of F(q), nonlinear with respect to the number of f electrons and only dependent on q (and not on the oxidation state or the chemical bonding of the ions), have been determined from atomic emission spectroscopic data on free atoms. Furthermore, we reported in previous papers12,30 that for several nonaqueous solvents Nugent's equation is still valid, the corrected experimental values (E°+ F(q)) being linearly related to q.…”

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

“…Moreover, as a well-known Lewis acid, Anderson and Morrey et al have studied the effect of AlCl 3 on the U state in ionic liquids and molten salt systems. − For example, under acidic conditions (AlCl 3 > 50 mol %), U­(III) and U­(IV) are more inclined to coordinate with low amounts of Cl – ions, which is completely different from alkaline melts (AlCl 3 < 50 mol %). In an alkaline melt, U­(III) and U­(IV) generally exist as UCl 6 n – ( n = 2 or 3).…”

Electrochemistry and Spectroscopy of UO2 2+ in Addic AlCl3-EMIC

“…Uranyl(VI) is stable in basic AICI3-BPC [13] and AICI3-EMIC [14] forming chloro-complexes of the type UOzCli^V'" which were reduced irreversibly to UC1|~. U(VI) introduced as UO3 into the acidic high temperature ionic liquid AlClj-NaCl reacted to give U(V) [15].…”