Affiliation:
1. Japan Atomic Energy Agency, Research Group for Aqueous Separation Process Chemistry, Nuclear Science and Engineering Directorate, Shirane 2-4, Tokai, Ibaraki, 319-1195, Japan
Abstract
Abstract
Optical absorption spectra of Np in 3 mol/dm3 nitric
acid at elevated temperatures were measured using an optical glass
cell with a water jacket having a light path of 1 cm. Molar
extinction coefficients of Np(VI), ε
T
M
–1 cm
–1, were obtained at various temperatures (297,
313, 334, 352, and 372 K). The values of ε
T were found to decrease with increasing temperature and
could be described by the equation ε
T =− 0.14T + 85.5, where T is the temperature. Oxidation of
Np(V) to Np(VI) in 3 M nitric acid at elevated temperatures
(336, 342, 354, and 362 K) was observed using the optical
glass cell. Oxidation of Np(V) was promoted by increasing the
temperature and proceeded as a pseudo-first order reaction with
respect to Np(V) concentration. The rate equation in the temperature
range of 336–362 K was obtained as follows:
− d[Np(V)]
t
/dt = 2.2 × 107 exp [− 65 × 103/(RT)][Np(V)]
t
, where R, T, and
[Np(V)]
t
indicate the gas constant, temperature, and Np(V)
concentration at time t, respectively.
Subject
Physical and Theoretical Chemistry
Cited by
7 articles.
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