Effects of ultrasonic pre-treatment on the flotation of ilmenite and collector adsorption

Abstract

Herein we investigate the flotation and possible adsorption mechanism on the surface of ilmenite and the changes in the surface composition of ilmenite before and after ultrasonic pre-treatment through flotation tests, Fourier-transform infrared (FTIR) spectroscopy, zeta potential measurement, X-ray photoelectron spectroscopy (XPS), and microcalorimetry. The flotation results reveal that, under optimum conditions, sonication has a remarkable effect on the flotation of ilmenite. The maximum flotation recoveries of raw and ultrasonically treated ilmenite in the pH range 4–5 are 43.17 and 89.54%, respectively. The zeta potential of the pre-treated ilmenite shifted toward negative values, thus shifting the iso-electric point from pH 6.2 to pH ∼4.2. The FTIR spectra and zeta potential values indicate that the ultrasonic pre-treatment helped enhance the chemical adsorption of oleate ions on the surface of ilmenite. The results of microcalorimetry analysis suggest that the adsorption heat released (−Qads) from ultrasonically treated ilmenite is more than that released from raw ilmenite. The XPS analysis confirmed that the relative content of Fe3+ increased from 36.87 to 61.84% following the ultrasonic pre-treatment for 5 min in the pH range 4–5. After the treatment, Fe2+ ions on the ilmenite surface are abundantly oxidised to Fe3+ ions. The significant conversion of Fe2+ to Fe3+ helped improve the flotation recovery of ilmenite over a wide pH range.