| Autor: |
Shilov, V. P., Yusov, A. B., Fedoseev, A. M., Peretrukhin, V. F., Delegard, C. H. |
| Předmět: |
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| Zdroj: |
Radiochemistry; Sep2008, Vol. 50 Issue 5, p460-465, 6p, 2 Charts, 2 Graphs |
| Abstrakt: |
The kinetics of U(IV) oxidation with atmospheric oxygen in NaHCO3 solutions was studied by spectrophotometry. In 1 M NaHCO3 at [U(IV)]0 = 20 mM, an induction period is observed, which virtually disappears with decreasing [U(IV)]0 to 1.0 mM. The induction period is caused by the fact that initially U(IV) exists in a weakly active polymeric form. Addition of U(VI) to the initial solution accelerates the oxidation. In a 1 M NaHCO3 solution containing 0.1–1.0 mM U(IV), the U(IV) loss follows the first-order rate law with respect to U(IV) and O2. The pseudo-first-order rate constants, bimolecular rate constants, and activation energy of the U(IV) oxidation were calculated. In dilute NaHCO3 solutions (0.5–0.01 M), the hydrolysis and polymerization of U(IV) become more pronounced. The autocatalysis mechanism presumably involves formation of a complex [U(IV) · U(VI)] with which O2 reacts faster than with U(IV). Oxidation of U(IV) occurs by the two-electron charge-transfer mechanism. [ABSTRACT FROM AUTHOR] |
| Databáze: |
Complementary Index |
| Externí odkaz: |
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