The kinetics and mechanism of the reduction of neptunium (VI) ions by uranium (IV) ions in nitric acid

Autor:	G. V. Koltunov, V. I. Marchenko, K. N. Dvoeglazov, Robin J. Taylor, Eduard Andreevich Mezhov, V. S. Koltunov, G. I. Zhuravleva
Rok vydání:	2002
Předmět:	chemistry.chemical_compound chemistry Nitric acid Neptunium Inorganic chemistry Kinetics chemistry.chemical_element Physical and Theoretical Chemistry Uranium Ion Nuclear chemistry
Zdroj:	Scopus-Elsevier
ISSN:	2193-3405 0033-8230
DOI:	10.1524/ract.2002.90.5_2002.259
Popis:	SummaryThe rapid reduction of NpO22+ions to NpO2+by U(IV) ions in an aqueous nitric acid solution has been studied and, in many ways, is similar in character to the same reaction in HClO4. The major difference is that in HNO3the reaction proceedsviatwo parallel routes. The first isviathe hydrolysed UOH3+ion, as in the reaction in HClO4and the second isviathe non-hydrolysed U4+ion. These parallel routes lead to the observed order of reaction with respect to H+ions being reduced from −1 in HClO4to −0.7 in HNO3. After accounting for the reaction mechanism the rate equation is described by:wherek8= 404 min−1,k19= 275 M−1min−1and β = 0.009 M at 10 °C and μ = 2. The activation energy was 66.5 ± 4.9 kJ mol−1. Nitrate ions had no effect on the reaction rate but sulphamic acid increased the observed rate, probably through catalysis by sulphate ions arising from sulphamic acid reaction with HNO2and hydrolysis.
Databáze:	OpenAIRE
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