Abstract

The depressant action of three cationic polymers of low molecular weight (with oxygenated carbonyl functional groups, esterified oxygen and nitrogen atoms, classified as polyamine-polyamides)in flotation ofiron ore was investigated and compared with the performance of the traditional starch/amine system. Dosing of starch and amine and pH value were firstly adjusted in laboratory tests with flotation cell.Laboratory tests were also performed by partially replacing starch by the cationic polymers and also by adding small dosages of them to the starch/amineadjusted condition. The cationic polymers showed lower performance relative to the traditional starch/amine system when partially replacing starch. However, gains of up to 4% in mass and metallurgical recoveries were obtained when they were added to the adjusted starch/amine system. This is probably due to adsorption of cationic polymers to the surface of iron oxides via hydrogen bonds and dipole-dipole interaction, added to synergistic effects with starch molecules. Two pilot tests were performed with column flotation, the first one with the starch/amine systemadjusted in laboratory, and the second one by adding 70 g/ton of the cationic polymers with the best performance in laboratory tests. The gains by using cationic polymers were also observed in pilot scale.