Long-Term γ-Radiolysis Kinetics of NO3 − and NO2 − Solutions

Radiolysis kinetics in NO3 − and NO2 − solutions during γ-irradiation were studied at an absorbed dose rate of 2.1 Gy·s−1 at room temperature. Air- or argon-saturated nitrate or nitrite solutions at pH 6.0 and 10.6 were irradiated, and the aqueous concentrations of molecular water decomposition prod...

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Bibliographic Details
Published in:The journal of physical chemistry. A, Molecules, spectroscopy, kinetics, environment, & general theory Molecules, spectroscopy, kinetics, environment, & general theory, 2011-05, Vol.115 (17), p.4270-4278
Main Authors: Yakabuskie, Pamela A, Joseph, Jiju M, Stuart, Craig R, Wren, J. Clara
Format: Article
Language:English
Subjects:
A: Kinetics, Spectroscopy
Gamma Rays
Hydrogen-Ion Concentration
Kinetics
Nitrates - chemistry
Nitrites - chemistry
Solutions
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Summary:Radiolysis kinetics in NO3 − and NO2 − solutions during γ-irradiation were studied at an absorbed dose rate of 2.1 Gy·s−1 at room temperature. Air- or argon-saturated nitrate or nitrite solutions at pH 6.0 and 10.6 were irradiated, and the aqueous concentrations of molecular water decomposition products, H2 and H2O2, and the variation in the concentrations of NO3 − and NO2 − were measured as a function of irradiation time. The experimental data were compared with computer simulations using a comprehensive radiolysis kinetic model to aid in interpretation of the experimental results. The effect of nitrate and nitrite, present at concentrations below 10−3 M, on water radiolysis processes occurs through reactions with the radical species generated by water radiolysis, •eaq −, •O2 −, and •OH. The changes in H2 and H2O2 concentrations observed in the presence of nitrate and nitrite under a variety of conditions can be explained by a reduction in the radical concentrations. The kinetic analysis shows that the main loss pathway for H2 is the reaction with •OH and the main loss pathways for H2O2 are reactions with •eaq − and •OH. Nitrate and nitrite compete for the radicals leading to an increase in the concentrations of H2 and H2O2. Post-irradiation measurements of H2, H2O2, NO2 − and NO3 − concentrations can be used to calculate the radical concentrations and provide information on the redox conditions of the irradiated aqueous solutions.
ISSN:1089-5639
1520-5215
DOI:10.1021/jp200262c