Spectroscopy and electrochemistry of uranium complexes in aluminum chloride-1-ethyl-3-methylimidazolium chloride

Thesis/Dissertation · Mon Jan 01 04:00:00 EST 1990

OSTI ID:6090548

Anderson, C J

The redox chemistry of UCl{sub 4} was investigated in the solvent AlCl{sub 3}-1-ethyl-3-methylimidazolium chloride (AlCl-EMIC), a room temperature ionic liquid. In basic solutions (<50 mol % AlCl{sub 3}) the reduction of U(IV) to U(III) on glassy carbon electrodes is reversible. Visible/near-IR spectroscopic data and potentiometric measurements for U(IV)/U(III) as a function of the basic composition of AlCl-EMIC indicate U(IV) and U(III) are both hexachloro anions. Diffusion coefficients were measured for the U(IV) and U(III) complexes by two methods. The values are comparable to those of transition metal hexachloroanionic complexes in the same solvent, supporting the assignment of UCl{sub 6}{sup 2{minus}} and UCl{sub 6}{sup 3{minus}}. The redox behavior of UO{sub 2}{sup 2+} was examined in acidic AlCl-EMIC (>50 mol and AlCl{sub 3}). UO{sub 2}{sup 2+} is reduced in bulk solution by a chloroaluminate species (AlCl{sub 4}{sup {minus}} or Al{sub 2}Cl{sub 7}{sup {minus}}) producing UCl{sub 6}{sup {minus}}. The kinetics of the reduction were investigated spectroscopically by monitoring the growth of UCl{sub 6}{sup {minus}} in the visible and near-IR regions of the spectrum. Two first order pathways were observed, with over 90% reducing by the slower pathway and less than 10% reducing by a faster reaction. The two pathways reflect a competition between the formation of a UO{sub 2}{sup 2+} chloroaluminate complex from UO{sub 2}Cl{sub n}{sup (2{minus}n)+} which undergoes slow reduction to UCl{sub 6}{sup {minus}}, and an outer-sphere electron transfer of UO{sub 2}Cl{sub n}{sup (2{minus}n)+} to UO{sub 2}Cl{sub n}{sup (1{minus}n)+} which quickly forms UCl{sub 6}{sup {minus}}. The faster pathway was also studied spectroscopically following the disappearance of a U(V) oxo-species in the near-IR. Cyclic voltammetric results of UO{sub 2}{sup 2+} solutions in acidic AlCl-EMIC are consistent with the spectroscopic data.

• Research Organization: Florida State Univ., Tallahassee, FL (United States)
• OSTI ID: 6090548
• Country of Publication: United States
• Language: English

Related Subjects

050400* -- Nuclear Fuels-- Feed Processing
11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS
ACTINIDE COMPLEXES
ACTINIDE COMPOUNDS
ALUMINIUM CHLORIDES
ALUMINIUM COMPOUNDS
CHALCOGENIDES
CHEMICAL REACTION KINETICS
CHEMICAL REACTIONS
CHEMISTRY
CHLORIDES
CHLORINE COMPOUNDS
COMPLEXES
ELECTROCHEMISTRY
ELECTROMAGNETIC RADIATION
ELECTRON TRANSFER
HALIDES
HALOGEN COMPOUNDS
INFRARED RADIATION
KINETICS
NEAR INFRARED RADIATION
OXIDES
OXYGEN COMPOUNDS
RADIATIONS
REACTION INTERMEDIATES
REACTION KINETICS
REDOX REACTIONS
REDUCTION
SPECTROSCOPY
URANIUM CHLORIDES
URANIUM COMPLEXES
URANIUM COMPOUNDS
URANIUM OXIDES
VISIBLE RADIATION
VOLTAMETRY