Effects of microwave pre-treatment on the flotation of ilmenite and titanaugite

The selective separation of titanium-containing minerals is industrially important. Microwave irradiation pretreatment can be used to modify the surface properties of minerals to promote selective flotation. However, the effects of MW treatment on titanium-containing minerals is not well understood. Therefore, in this study, we investigated the effects of microwave treatment on the flotation behaviour of ilmenite and titanaugite in a mixture of these minerals. The effects of this pre-treatment method were investigated by various techniques, including flotation tests, scanning electron microscopy (SEM), inductively coupled plasma-optical emission spectrometry (ICP-OES), zeta potential measurements, X-ray photoelectron spectroscopy (XPS), and Fourier-transform infrared (FTIR) spectroscopy. The flotation tests results reveal that, under the optimum microwave conditions (800 W, 450 s), microwave irradiation has a remarkable effect on the flotation of ilmenite but no significant effect on the floatability of titanaugite at pH 6.0. The results of the SEM and ICP-OES analyses indicate that microwave irradiation promotes the dissolution of Ca2+ and Mg2+ ions from the titanaugite surface, whereas the dissolution of these ions from ilmenite is limited. Further, the zeta potential of the microwave-irradiated ilmenite shifted toward negative values, and the isoelectric point shifted from pH 4.9 to pH similar to 1.9. In addition, the XPS results reveal that microwave irradiation facilitates the conversion of Fe2+ to Fe3+ on the mineral surfaces. The FTIR spectra and zeta potential values indicate that microwave irradiation can enhance the chemical adsorption of oleate ions on the surface of the ilmenite. After microwave irradiation, the effects of both the dissolution of Ca2+ and Mg2+ ions and the oxidation of Fe2+ to Fe3+, the floatability of ilmenite was significantly improved, whereas that of titanaugite was not changed significantly.