Mechanochemical reduction of SrSO4 by Mg

Mixtures of celestite concentrate (98% purity) and magnesium powders (97% purity) with a molar ratio of 1:4 were milled for increasing times. The temperature–time profile indicated a sudden increase in vial temperature between 10 and 11 min for the stoichiometric mixture of SrSO4–Mg, whilst only 8–9 min were required with a 25% excess of magnesium. X-ray diffraction showed that the reaction produced SrS and MgO, increasing the milling time beyond that necessary for ignition did not have any major effect on the products. The results showed the mechanochemical reaction was highly exothermic and initiated as mechanically induced self sustaining reaction (MSR). After milling, the products were washed with hot water (T = 80 °C) for 2 h to separate the soluble SrS from the insoluble MgO.