Study of N, N-bis (2-hydroxyethyl) -N-methyl dodecyl ammonium chloride as the novel collector in selective flotation separation of quartz and hematite

A quaternary ammonium salt, N, N-bis (2-hydroxyethyl)-N-methyl dodecyl ammonium chloride (BHMDC), with high surface activity, was screened and firstly introduced in the reverse flotation of hematite ores based on Density Functional Theory (DFT) calculation and surface tension measurement. The interaction mechanism of BHMDC on the surfaces of quartz and hematite was studied by zeta potential measurement, X-ray photoelectron spectroscopy (XPS) and Fourier transforms infrared spectroscopy (FTIR), respectively. The results of DFT calculation and surface tension measurement indicated that BHMDC had higher selectivity and hydrophobicity than dodecylamine (DDA). The analyses of zeta potential measurement, FTIR, and XPS demonstrated that the adsorption of BHMDC on hematite and quartz surfaces were mainly dependent on hydrogen bonding and electrostatic interaction. Due to the more active sites (O atoms), the weaker charge and larger size of polar groups, BHMDC had better simulation results in performance than DDA, especially in selectivity. The flotation tests showed that BHMDC exhibited better flotation performance, which was consistent with the results of DFT calculation. And the efficient separation of hematite and quartz within the wide pH value range (4.0-10.0) was determined, which was also confirmed by zeta potential measurement. It also indicated that BHMDC was an excellent collector in the reverse flotation of hematite ores with great industrial potential, which could obtain the concentrate with the Fe grade of 65.37% and recovery of 88.92%.