Abstract:  In order to investigate the effect of substituent number and type on flotation performances of cationic collector，a series of C12 alkyl amines were selected to conduct flotation separation of quartz and hematite. Collecting abilities of cationic collectors was investigated by single mineral flotation. And also，their effect on selectivity of cationic collectors was studied by flotation separation of artificially mixed quartz and hematite. Flotation results indicated that，collecting abilities of cationic collector were decreased with methyl group introduction. Flotation recoveries of hematite and quartz were reduced with the increasing of methyl number. However，flotation selectivity of cationic collector could be increased due to sharply re duce of hematite flotation recovery. And separation efficiency for artificially mixed quartz and hematite was increased gradually. Introduce of hydroxyl and amino group can enhance the flotation of quartz and separation efficiency for artificially mixed minerals. Nevertheless，the increase for separation efficiency was not too obviously for flotation recovery of hematite was also enhanced with amino group introduction. Quantum chemistry calculation results indicated that，cross sectional area of polar group for cationic collectors was enhanced with methyl group introduction to enlarge the steric hindrance between cationic col? lectors and mineral surface. This results in the decrease of collecting abilities and increase of separation selectivity of cationic collector. Introduce of amino group can increase the total charge of polar group to strengthen the electrostatic attraction between cationic collector and mineral surface. And the hydrogen bond attraction between cationic collector and mineral surface was strengthened with the increase of sectional area of polar group for introduce of hydroxyl group. This results in the increase of collecting ability and flotation selectivity of cationic collectors. In future，getting and quantifying correlation parameters of these substituents，and then explicating the relationship between substituent parameters and flotation performance of cationic collectors would be benefit to establish a new design method for cationic collector.

Key words: Cationic collectors, Substituents, Collecting ability, Selectivity