Mechanism of a novel proxan-sodium–cetyltrimethylammonium bromide combined collector on the flotation removal of pyrite from high-sulphur bauxite

China's proven reserves of high-sulphur bauxite amount to over 100 million tons. Traditional roasting desulphurization processes suffer from problems such as equipment corrosion, poor desulphurization efficiency and poor alumina product quality. A novel combined collector proxan-sodium–cetyltrimethylammonium bromide (PXS–CTAB) was prepared by combining PXS with CTAB, and was applied to the research on the flotation of high-sulphur bauxite to remove pyrite. The effect of the ratio and dosage of PXS–CTAB on the flotation indices of high-sulphur bauxite was investigated. Surface contact angle, Fourier-transform infrared and X-ray photoelectron spectroscopy techniques and molecular simulation were used to reveal the mechanism of action of PXS–CTAB on the surface of pyrite. The results showed that when the PXS–CTAB ratio was 1 : 1 and the dosage was 240 g t−1, the sulphur content in the aluminium concentrate decreased from 5.46% to 0.62%, with a desulphurization rate of 90.39%. The Al2O3 content increased to 59.65%, and the recovery of Al2O3 improved to 88.27%. After treatment with PXS–CTAB, the surface contact angle of pyrite increased by 7.48°, significantly enhancing its hydrophobicity and thereby improving the flotation effect. This study can provide certain data support and theoretical guidance for the flotation of high-sulphur bauxite.