Synthesis of a novel hydroxyl quaternary ammonium collector and its selective flotation separation of quartz from hematite

The quaternary ammonium salt collectors display great application prospects in minerals flotation, and introducing the second polar group has been an effective method to enhance the performance of flotation reagents. In this study, the hydroxyl group was introduced into quaternary ammonium salt to design and synthesize a novel containing hydroxyl group quaternary ammonium salt collector dodecyl hydroxyethyl dimethyl ammonium bromide (DHDAB) for the flotation desilication of hematite, which was characterized by Fourier transform infrared spectroscopy (FT-IR), mass spectrometry, and nuclear magnetic resonance (NMR). Based on the reverse flotation desilication system of hematite, the differences in flotation performance of DHDAB and dodecyl trimethyl ammonium bromide (DTAB) were compared, and the flotation separation behaviors of DHDAB to quartz and hematite were also studied by micro-flotation tests. Both DHDAB and DTAB showed great pH adaptability, and DHDAB had better flotation selectivity than DTAB through flotation studies. The selective flotation separation mechanism of DHDAB to quartz and hematite was also analyzed by zeta potential tests, FT-IR analyses, contact angle tests, X-ray photoelectron spectroscopy (XPS) tests and density functional theory (DFT) analyses, meanwhile, the influence mechanism of the hydroxyl group on the performance of collectors was also studied. The contact angle test results showed that the surface hydrophobicity of quartz and hematite treated by DHDAB was more different. These results also indicated that DHDAB was selectively adsorbed on the mineral surface mainly through electrostatic attraction and hydrogen bonding. Introducing the hydroxyl group into DHDAB could produce stronger hydrogen bonding, increase the interaction site with the quartz surface, and increase the steric hindrance to enhance the selectivity.