Investigation on the reaction between MgO–CaO–CaF2 and Al–C powders to extract magnesium under atmospheric pressure

In order to utilize the carbon resource, a novel process was developed to extract magnesium from magnesia by the reaction between MgOCaOCaF2 and Al-C powders reinforced using mechanical activation technique under atmospheric pressure at 1223 K (950 °C). The effects of C, CaO, CaF2, and ball milling time on the reduction ratio of magnesia was investigated. It was found that the reduction ratio of magnesia is shown to increase with an increase of the variables being investigated. Additionally, the reactivity of Al was enhanced by the addition of C powder into reactants during the ball milling process. Moreover, the reduzate were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) coupled with energy-dispersive X-ray spectroscopy (EDS) to reveal the reaction mechanism. The results indicated that the reaction mechanism was different from the previous report owing to the addition of C powder during high energy ball milling process, and the reaction process is the reduction of MgO, the formation of 12CaO⋅7Al2O3, MgAl2O4 and CaAl1.9O4C0.4 when the content of CaO is 20–30 wt%, and when the content of CaO is more than 30 wt%, the MgAl2O4 phase is disappeared. Moreover, with the addition of CaF2, the reduction reaction is expressed as the reduction of MgO, the formation of 11CaO⋅7Al2O3⋅CaF2 and CaAl1.9O4C0.4.