Optimization and mechanism in preparing active magnesium oxide from magnesite

Abstract

Active magnesium oxide is an important magnesium product due to its unique properties. Magnesium oxide with high activity was obtained by optimizing the technological parameters including calcination temperature and residence time. Thermal decomposition process, morphology, specific surface area and crystal structure were determined by TG-DSC thermal analyzer, optical and scanning electron microscope, specific area analyzer and X-ray diffractometer, respectively. Results indicate that magnesium oxide products prepared during the early stage are characterized by small particle size, imperfect crystal structure, large specific area and high activity, and as residence time increases, particle size grows up gradually and crystal structure becomes perfect, so activity goes poor. Under conditions of higher calcination temperature, two processes involving decomposition of magnesite and crystallization of magnesium oxide proceed simultaneously, resulting in magnesium oxide with lower activity. Therefore, highly active product with \({\Delta n}_{\rm Cl^-}\)of 40.5 mol kg−1 is prepared at a relatively low temperature of 600 °C for 9 h.