MgSO4 carbothermic reductive decomposition to produce a highly reactive MgO powder

Abstract

Magnesium sulphate is commonly present in industrial wastes due to Mg’s presence in the structure of various minerals and the fact that sulphuric acid leaching is widely used. MgO appears as a possible pH neutralizing agent that can be obtained by decomposition of MgSO4. However, at 1500 K, the temperature where this decomposition occurs, the oxide formed cannot be used for this purpose. The thermodynamic study suggests that in the presence of reducing agents, such as carbon, decreasing the decomposition temperature makes the formed oxide viable for this use. The objective of the work is an evaluation of the behaviour of the reaction system constituted by MgSO4 and charcoal. The study also contemplates the obtained materials characterization to verify the MgO formation and evaluating how the properties of the material are suitable for its use as a pH regulator. Thus, in addition to the scanning and X-ray diffraction electron microscopy techniques, the quantification of the reactivity of the product in acid solutions is also expected. The analysis performed with the variables of excess reducing agent and temperature showed that temperature is the variable that most influences the decomposition of MgSO4. The experiments at 1173 K and 20, 25 and 30 min were the ones that indicated the best experimental results of conversion, reaching a conversion close to 100%. The characterization analysis, in XRD and SEM/EDS, indicated that MgO was formed at the end of the reaction. Reactivity test indicates that the obtained MgO can be used as a pH regulator.