In this study, an imidazole ionic liquid (dodecyl-tri-methylimidazolium chloride) was employed as a collector to separate quartz from phosphorite. The micro-flotation experiments of a single mineral found that it had selective collecting ability for quartz than phosphorite. Mixed mineral flotation experiments confirmed that efficient separation results could be obtained using the imidazole ionic liquid as the collector. A concentrate with a 31.44% grade of phosphorite could be obtained with a 0.285 kg/Mg collector dosage at neutral pH, which was much better than the traditional collector dodecylamine. The adsorption mechanism of the imidazole ionic liquid on the surface of phosphorite and quartz was investigated by contact angle and zeta potential measurements, Fourier transform infrared and X-ray photoelectron spectroscopy analyses. These results showed that the adsorption of imidazole ionic liquid at the quartz surface was stronger than that of phosphorite, and the collector adsorbability difference between quartz and phosphorite resulted in the efficient flotation separation. Consequently, the dodecyl-tri-methylimidazolium chloride salt is an effective collector for reverse flotation of quartz from phosphorite.