Abstract: DL-1 is a newly anionic reverse flotation collector developed by Northeastern University.In order to test the floating properties，mixed magnetic concentrate from Qidashan Dressing Plant with Fe grade of 46.02% was used to make reverse flotation tests，and the mechanism in quartz reverse flotation by DL-1 is discussed with Zeta potential measurement and infrared spectrum analysis.The results showed that：①Iron concentrate with Fe grade of 65.38%，recovery of 89.56% was obtained through closed-circuit reverse flotation flowsheet of one roughing，one scavenging，and middles back to the flowsheet in turn with normal temperature and DL-1 as collector; DL-1 can endure temperature changes，and high efficiently collecting quartz at a lower dosage of CaCl₂.②There are electrostatic repulsion between quartz and DL-1 with pH of 9~12 in aqueous alkaline solution，and can be weakened by activation of CaCl₂ to quartz; electrostatic/chemical adsorption may occur between quartz activated by Ca2+ and DL-1 with pH of 9~11.45，there are strong electrostatic attraction of quartz activated by Ca²⁺ to DL-1 with pH>11.45，therefore DL-1 can well adsorb and collect quartz at pH range of 9~11.45.③There are physical adsorption，hydrogen bond and chemical adsorption coexist between DL-1 and quartz surface with pH of 11.45，DL-1 can also well collect quartz without Ca2+ activation.

Key words: Anionic collector DL-1, Quartz, Mixed magnetic concentrate, Reverse flotation, Mechanism