(EN) A method for ion flotation of copper ions uses as the flotation reagent a cationic surfactant of formula (I), wherein R1 is a C10-C18 alkyl group, R3 is a lower alkyl group, or benzene ring optionally substituted with one or more lower alkyl groups, and R2 and R4 are lower alkyl groups; or R1, R2 and R4 are methyl groups; R3 is a benzene ring substituted with a C10-C18 alkoxy group; and X is a halogen atom.