Flotation separation of quartz from gypsum using benzyl quaternary ammonium salt as collector

Phosphogypsum is a kind of industrial by-product, which could be used as building materials instead of natural gypsum after removing impurities. Flotation is an effective method to remove the silicon-containing impurity quartz in the phosphogypsum. In this work, a surfactant tetradecyl dimethyl benzyl ammonium chloride (TDBAC) was first used as the collector of quartz to be separated from gypsum. The flotation behaviors of quartz and gypsum were investigated by micro-flotation experiments. The flotation mechanisms were analyzed through Zeta potential testing, Fourier Transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS). Micro-flotation results show that TDBAC exhibited outstanding collecting capacity and selectivity for quartz over the wide pH range of 2.5–9.5. FTIR results declared that TDBAC could be successfully adsorbed on the surface quartz. The analysis results of zeta potential and XPS indicate that the interaction mechanisms of TDBAC with quartz were involved electrostatic attraction and hydrogen-bond interaction, whereas the adsorption onto gypsum surface was only by the weak electrostatic attraction and hydrogen-bond interaction. The results of this work showed that TDBAC is expected to be an effective collector of quartz for removing silicon impurity from the industrial phosphogypsum.