Influence of microwave irradiation on ilmenite flotation behavior in the presence of different gangue minerals

• Microwave irradiation (MWIR) improves flotation recovery of ilmenite.
• Microwave improves floatability of iron containing gangue minerals.
• Fe3+ ions are important potential determining ions in the ilmenite flotation.
• Microwave improves selectivity index when gangues contains lower amount of Fe.
• The less Fe in gangue minerals the more increase in ilmenite separation efficiency.

As a pretreatment method, microwave irradiation was applied to modify ilmenite surface properties and to improve its flotation behavior in the presence of different gangue minerals including olivine, pyroxene, tremolite, clinochlore and quartz. The flotation experiments were carried out in both micro (Hallimond-tube) and laboratory (flotation cell) scales. The microflotation experiments showed that the ilmenite surface irradiation converts Fe2+–Fe3+ ions, characterized by XPS analysis, improving the floatability. This is due to the increase of oleate adsorption and the formation of more insoluble ferric iron oleate as evidenced by FTIR analysis and zeta potential measurements. In addition, this pretreatment decreases the consumption of flotation reagents. The microwave irradiation does not have a significant effect on surface properties and floatability of quartz. In laboratory scale flotation experiments, when quartz is the main gangue mineral, the TiO2 grade and recovery of flotation concentrate improved from 27.1% to 28.3% and 85.3% to 92.7%, respectively by using microwave irradiation. In the presence of tremolite and clinochlore containing almost 12.4% Fe, the microwave irradiation improved the TiO2 grade and recovery from 21.3% to 22.1% and 71% to 82.5%, respectively. In the case of olivine and pyroxene with 30.1% Fe, the recovery of TiO2 increases from 66.9% to 69.1%. In the flotation of the ore sample containing 24.5% Fe, the microwave irradiation improves the recovery of TiO2 in the ilmenite concentrate from 65.4% to 76.2%. In a general result, in the flotation of ilmenite from different gangue minerals, the separation efficiency and selectivity index have a negative correlation with the iron content of gangue minerals.