Kinetics and mechanism of the reaction between plutonium(III) and chlorine in chloride solutions |
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| Affiliation: | 1. Key Laboratory for Applied Surface and Colloid Chemistry, National Ministry of Education, Shaanxi Engineering Lab for Advanced Energy Technology, School of Materials Science and Engineering, Shaanxi Normal University, Xi’an 710119, China;2. MOE Key Laboratory of Materials Physics and Chemistry Under Extraordinary Conditions, Shaanxi Key Laboratory of Condensed Matter Structures and Properties, School of Physical Science and Technology, Northwestern Polytechnical University, Xi’an 710072, China;3. Dalian National Laboratory for Clean Energy, iChEM (Collaborative Innovation Center of Chemistry for Energy Materials), Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023, China;1. Department of Civil and Environmental Engineering, KAIST, 373-1 Guseong-dong, Yuseong-gu, Daejeon 305-701, Republic of Korea;2. Petroleum and Gas Laboratory, Korea Institute of Energy Research, Daejeon 305-343, Republic of Korea;1. Laboratory of Nuclear Energy Chemistry, Institute of High Energy Physics, Chinese Academy of Sciences, Beijing, 100049, China;2. Key Laboratory of Superlight Materials and Surface Technology, Ministry of Education, College of Material Science and Chemical Engineering, Harbin Engineering University, Harbin, 150001, China;3. Reactor Engineering and Safety Research Center, China Nuclear Power Technology Research Institute Co., Ltd, China General Nuclear Power Corporation, Shenzhen, 518000, China;1. School of Chemistry, University of Manchester, Oxford Road, Manchester, M13 9PL, UK;2. Pacific Northwest National Laboratory, Richland, WA, 99354, USA;3. Sellafield Ltd., Sellafield, Seascale, Cumbria, CA20 1PG, UK;4. National Nuclear Laboratory, Central Laboratory, Sellafield, Seascale, Cumbria, CA20 1PG, UK;1. Department of Civil and Environmental Engineering and Earth Sciences, University of Notre Dame, Notre Dame, IN, 46556, USA;2. Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, IN, 46556, USA |
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| Abstract: | Oxidation of plutonium(III) to (IV) by chlorine in chloride solutions follows an apparently first order rate law with respect to both the reactants, and the rate is independent of acidity. At room temperature, and with 0·01 M initial plutonium concentration and about 0·025 M initial chlorine concentration, the specific reaction rate, k′ increases from 0·04 to 2·8 × 10−2 min−1, as the hydrochloric acid concentration of the medium changes from 1·5 to 8·0 M. In solutions having constant hydrochloric acid, k′ increases at first linearly with initial chlorine concentration and finally approaches a limiting value for a given initial plutonium concentration. The limiting values in 7·0 M hydrochloric acid with 0·025 M of chlorine concentration are 0·6, 1·2 and more than 2·2 × 10−2 min−1 respectively with 0·005, 0·01 and 0·02 M initial plutonium concentrations. The rate of oxidation is relatively very slow at room temperature in chloride free perchloric acid solutions, while in solutions containing mixture of hydrochloric and perchloric acids, it is markedly increased by chloride ion concentration for a given total molarity of the acid mixture as well as by the total molarity having fixed concentration of hydrochloric acid, showing thereby that the rate is influenced both by chloride ions as well as by ionic strength of the medium. Thermodynamic quantities of activation at 26°C have been calculated from the experimentally determined activation energy of the reaction, the average value of which is 16·0 ± 1·8 kcal/mole.A mechanism is suggested according to which a transient species is assumed to be formed in steady state concentration by the action of Cl3− ions on Pu(III) ions, and the rate is determined by the reaction between these transient species and Pu(III) ions. |
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