Studies on the dissolution kinetics of ceramic uranium dioxide particles in nitric acid by microwave heating

Abstract The kinetic study of Amazon metakaolin dissolution was performed with the application of the shrinking core model for spherical and ‘flat plate’ particles with constant size. The Amazon kaolin was calcinated at 700 ºC in order to produce metakaolin. This metakaolin was leached with 5% excess nitric acid at 70, 80 and 95±3 ºC for 3 h. Samples were collected every 15 min and subjected to aluminum analysis. The acid leaching was a chemically controlled process. The spherical morphology showed better fit than the flat plate particles when taking into account the regression coefficients. 91.58 kJ/mol of activation energy was found as well as an aluminum leaching reaction of the first order. The results found in this work using 5% excess acid and Amazon kaolin were consistent with previous research results using excess acid above 50% and standard kaolin.

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Dissolution kinetics of metallic zinc obtained from spent zinc‐carbon batteries in nitric acid solutions

Environmental Progress & Sustainable Energy ◽

10.1002/ep.13553 ◽

2020 ◽

Author(s):

Nizamettin Demirkıran ◽

Merve Şenel

Keyword(s):

Nitric Acid ◽

Dissolution Kinetics ◽

Metallic Zinc ◽

Acid Solutions ◽

Nitric Acid Solutions ◽

Kinetics Of

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A method for phenomenological and chemical kinetics study of autocatalytic reactive dissolution by optical microscopy. The case of uranium dioxide dissolution in nitric acid media

EPJ Nuclear Sciences & Technologies ◽

10.1051/epjn/2017026 ◽

2018 ◽

Vol 4 ◽

pp. 2 ◽

Cited By ~ 1

Author(s):

Philippe Marc ◽

Alastair Magnaldo ◽

Jérémy Godard ◽

Éric Schaer

Keyword(s):

Nitric Acid ◽

Optical Microscopy ◽

Chemical Kinetics ◽

Uranium Dioxide ◽

Chemical Elements ◽

Dissolution Kinetics ◽

Purex Process ◽

Acid Media ◽

Reactive Dissolution ◽

Physico Chemical

Dissolution is a milestone of the head-end of hydrometallurgical processes, as the stabilization rates of the chemical elements determine the process performance and hold-up. This study aims at better understanding the chemical and physico-chemical phenomena of uranium dioxide dissolution reactions in nitric acid media in the Purex process, which separates the reusable materials and the final wastes of the spent nuclear fuels. It has been documented that the attack of sintering-manufactured uranium dioxide solids occurs through preferential attack sites, which leads to the development of cracks in the solids. Optical microscopy observations show that in some cases, the development of these cracks leads to the solid cleavage. It is shown here that the dissolution of the detached fragments is much slower than the process of the complete cleavage of the solid, and occurs with no disturbing phenomena, like gas bubbling. This fact has motivated the measurement of dissolution kinetics using optical microscopy and image processing. By further discriminating between external resistance and chemical reaction, the “true” chemical kinetics of the reaction have been measured, and the highly autocatalytic nature of the reaction confirmed. Based on these results, the constants of the chemical reactions kinetic laws have also been evaluated.

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