Thermogravimetric Analysis and Kinetic Study of the Calcification Roasting of Vanadium Slag

The roasting is the key step for the extraction of vanadium from vanadium slag by calcification roasting–acid leaching process. In this study, thermogravimetric analysis and kinetic study of vanadium slag in the presence of calcium oxide was investigated. The maximum oxidation degree was slightly increased by increasing temperature from 700 to 900 °C then almost unchanged further increasing temperature to 1000 °C. The reaction mechanism was analyzed through both Sharp method and ln-ln method. Results showed that the mechanism the reaction in the α range of 0.1–0.8 corresponded to the random nucleation and subsequent growth, as represented as (G(α) = [−ln(1−α)]^1/3 = kt. The apparent activation energy was calculated to be 3.5 kJ/mol according to Arrhenius equation.