[en] In this study, the role of passive potential and immersion time in the responses of Ta, including electrochemical and passive, in HNO₃ solution (0.1 M) are investigated. Plots obtained from electrochemical impedance spectroscopy (EIS) reveal that the resistance of passive layers formed on the pure Ta against corrosion raises as the passive potential and immersion time increase. Moreover, Mott–Schottky (M–S) analysis is done to find the semiconducting properties of the given passive layers. The results indicate that passive potential and immersion time highly influence the concentration levels of donors through semiconductive behavior of pure Ta in the given solution is similar to that of n-type. The plots show that lower densities of donors in passive films deteriorate the resistance of the pure Ta against corrosion due to higher immersion time and passive potential. Moreover, the sensitivity of potentiality of flat bands to potentiality of passive films is another finding revealed by M–S plots. (paper)

[en] Palladium complexation in concentrated nitric acid solutions was studied by UV/Vis absorption spectrophotometry. The ionic strength of the solutions was fixed to I = 1, 3, or 5 mol dm^-3 (M) by mixing of HNO₃ and HClO₄. The major palladium species were found to be Pd²⁺, PdNO₃⁺, and Pd(NO₃)₂. The formation constant of PdNO₃⁺ was determined to be β₁ = 1.32 (I 1 M), 1.49 (I = 3 M), or 1.47 (I = 5 M), while that of Pd(NO₃)₂ to be β₂ = 0.45 (I = 3 M) or 0.14 (I = 5 M). (author)

No abstract available

[en] The diamide N,N,N',N'-tetraoctyldiglycolamide (TODGA) was synthesized and characterized. The prepared TODGA was applied for extraction of Ce(III) from nitric acid solutions. The equilibrium studies included the dependencies of cerium distribution ratio on nitric acid, TODGA, nitrate ion, hydrogen ion and cerous ion concentrations. Analysis of the results indicates that the main extracted species is Ce(TODGA)₂(NO₃)₃HNO₃. The capacity of Ce loading is approximately 45 mmol/L for 0.1 M solution of TODGA in n-hexane. Finally, the thermodynamic parameters were calculated: K (25 deg C) = 3.8 x 10³, ΔH = -36.7 ± 1.0 kJ/mol, ΔS = -54.6 ± 3.0 J/K mol, and ΔG = -20.4 ± 0.1 kJ/mol. (author)

[en] Acetohydroxamic acid (AHA) is an important complexant/reductant for Pu(IV) in the UREX process. It decomposes in the presence of nitric acid. In literature, its decomposition kinetics in nitric acid is traditionally reported as pseudo-first order reaction. In this study, new experimental data were reported for kinetics experiments under wide concentration conditions. It was found that the decomposition reaction was first order with respect to both the components hence overall second order. (author)

[en] The primary goal of this work was to evaluate the effectiveness of the chop-leach process, with nitric acid dissolvent. The results of this study show that this processing technique is appropriate for applications in which a low free acid and moderately high U content are desired

[en] The conditions of pertechnetate ion precipitation with ferroin nitrate in nitric acid solutions were determined. The effect of precipitation condition on the composition and structure of ferroin pertechnetate complexes was analyzed. At aging of the precipitate in the mother liquor the formation of nitrosyl group in the complex was found, which is confirmed by appearance in the IR spectrum of the band at 1700 cm"-"1 belonging to the coordinated nitrosyl group. Analysis of the IR spectra of ferroin perrhenate and pertechnetate complexes showed that coordinated nitrosyl group is formed only in the presence of technetium in the complex structure. (author)

[en] A simple and rapid method for the determination of total uranium in electrolyser samples is described. NaNO_2 is used as an oxidizing agent for complete conversion of Uranous to Uranyl and also for destruction of hydrazine present in the sample. The molar absorption coefficient of uranyl ion was found to be 8 liter/mole-cm. The correlation coefficient was found to be 0.999. The relative standard deviation for the estimation of uranium was found to be well within limits required for process control analysis. (author)

[en] The kinetics of back-extraction of Pu(IV) from 30% Tri-Butyl-Phosphate/Odourless Kerosene (TBP/OK) into a nitric acid solution containing N,N-dimethylhydroxylamine (DMHAN) have been investigated using a Lewis cell. The different parameters affecting the back-extraction rate of Pu(IV) such as plutonium, nitric acid, DMHAN concentration in addition to temperature, stirring speed were separately studied and a rate equation was deduced. The activation energy of this process is 28.4 kJ/mol. (author)

[en] Highlights: • Nitric acid treated NaBiO₃ showed good activity for degrading organic pollutants in dark. • Singlet oxygen was produced as dominant active species by nitric acid-treated NaBiO₃. • A mechanism of singlet oxygen generation was proposed. • Singlet oxygen was generated from the metastable Bi(III)O₆ octahedron pseudo-interface. • Nitric acid treated NaBiO₃ might be deactivated and reactivated by different methods.