Abstract: Pure quartz flotation experiments and reverse flotation of practical concentrate from magnetic separation of magnetite are conducted in order to compare the collecting ability of dodecylamine，dodecyl-propyl ether amine and dodecyl-amine ethoxylate on quartz.The adsorption heat，adsorption quantity，and the adsorption enthalpy are analyzed to compare the intensity of the three collectors to quartz surface.Pure mineral flotation results indicated that，the optimum pH for the three collectors is 6~8，and collecting ability of dodecyl-amine ethoxylate is better than the other two collectors at any pH value.Reverse flotation results of the practical sample showed that，better performance can be obtained by using dodecyl-amine ethoxylate on a lower dosage than the other two，which revealed that dodecyl-amine ethoxylate not only has higher collecting ability but also better selectivity.The adsorption heat，adsorption quantity，and the adsorption enthalpy analysis show that the adsorption of the three collectors on quartz is spontaneous，and all belongs to physical adsorption.The adsorption performance of dodecyl-amine ethoxylate on quartz is better than the other two at any pH value，which support the flotation results well.

Key words: Dodecyl-amine ethoxylate, Quartz, Collecting ability, Adsorption