Formation of micro-fractures on an oolitic iron ore under microwave treatment and its effect on selective fragmentation

In this work the fragmentation of a Chinese oolitic iron ore along the boundaries of hematite and gangue minerals by means of microwave pretreatment was studied in order to liberate hematite from the ore at coarse particles. The experimental results have shown that a large amount of intergranular fractures formed on the oolitic iron ore after being treated by microwave radiation at an appropriate frequency and potential. The formation closely correlated with the power and time of microwave exposed to the ores. Also, microwave radiation was advantageous over high-pressure compression for the fracture formation, because the former only generated fractures while the latter simultaneously formed fractures and closed up existed fractures. Following microwave pretreatment, the oolitic iron ore was ground by using a stirred grinding mill. It is shown that the pretreatment increased the liberation of hematite and gangue minerals (quartz and apatite) about 20%–30% at the same particle size ranges.