Oxidation of the Irshansk Ilmenite Ore in Microwave Heating

The general chemical and phase composition of the ilmenite concentrate from the Irshansk deposit was determined. The content of titanium (in terms of TiO₂) in this concentrate was more than 50 wt.%. Ilmenite was the main phase component, which partially turned into pseudorutile through secondary processes. The concentrate was oxidized using microwave heating. Prior to microwave heating, particles of the starting ilmenite concentrate were ground for 3 min in a planetary-ball mill to an average size of 10 μm. A 100 g sample of the ground concentrate was heated for 30, 60, 90, and 120 min. In the heating for 30 min, pseudorutile disintegrated and pseudobrookite formed. Subsequent heating for 60 and 90 min led to the formation of rutile and increased the amount of pseudobrookite. Microwave heating for 120 min resulted in the complete decomposition of ilmenite. Pseudobrookite, rutile, and quartz were identified in an averaged sample by X-ray diffraction. Iron oxides were not found in the averaged sample. Interaction of the ilmenite concentrate sample with air during heating led to intensive surface oxidation of the material to form a larger amount of rutile and to release of iron oxide from the pseudobrookite as hematite. Electron microscopy of the oxidized particles revealed that titanium was mainly contained in fine concentrate subparticles up to 1 μm in size, and impurities (silicon and aluminum compounds) formed coarser agglomerates. The sizes of ore macroparticles hardly changed after microwave heating. Comparison of the effects from microwave and conventional heating on the ilmenite concentrate showed that heating in a resistance furnace for 120 min did not result in complete oxidation of ilmenite even at higher temperatures. Additional grinding of the starting ilmenite concentrate increased the heating and oxidation temperatures of the material subjected to microwave processing.