Oxidation of cobaltite
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Authors
Wang, Guoxin
Issue Date
1993
Type
Thesis
Language
en_US
Keywords
Control Of Arsenic , Oxidation Of Cobaltite , Oxidative Roasting , Leaching Processes , Process Mineralogy , X-ray diffraction , Reflected Light Microscopic Analyses , Electron Microscopic Analyses , Roasted Cobaltite Concentrations , Crystal Structural Change , Arsenic , Temperature Dependent , Differential Thermal Analysis , Exothermic Reaction Peaks , Kinetics Of Oxidation , Pore-blocking Kinetics , Shrinking Core Kinetics Model , Activation Energy , Mackay Theses and Dissertations Grant Collection
Alternative Title
Abstract
The control of arsenic in the oxidation of cobaltite is important in oxidative roasting/leaching processes. The process mineralogy of the oxidation of cobaltite was evaluated based on the performances of X-ray diffraction, reflected light microscopic and scanning electron microscopic analyses on the roasted cobaltite concentrates. Oxidative roasting below 550°C did not show any crystal structural change in cobaltite but heating to 650°C, yielded Co-As-oxide whose composition varied. Direct oxidation of cobaltite to cobalt oxides with traces of arsenic was observed by roasting at 750°C or above. The arsenic concentration within the particles decreased with the increase of temperature. The arsenic removal from the lattice of cobaltite was found to be temperature dependent in the oxidation process. Differential Thermal Analysis on pure cobaltite showed that three exothermic reaction peaks existed in the oxidation process. The overall kinetics of oxidation of cobaltite have been studied for temperatures up to 900°C, based on experiments in P-E TGS-2 TGA system. Up to temperatures of 640°C, pore-blocking kinetics gave a satisfactory fit of the data, whereas above 670°C, the shrinking core kinetics model was applicable. The activation energy was 479 KJ/mol below 565°C and 265.5 KJ/mol above 670°C.
Description
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Citation
Publisher
University of Nevada, Reno
License
In Copyright(All Rights Reserved)