The infrared spectra of amine collectors used in the flotation of iron ores

Inverse froth flotation is the most used concentration method for itabiritic iron ores, where the quartz gangue is floated, and the iron oxides are kept depressed by starches; medium-chain etheramine acetates are the cationic collectors used. Since there is a lack of thorough studies on the infrared spectroscopy of these reagents (and by other similar techniques), an investigation on the band assignment in the infrared spectra of a typical etheramine acetate was carried out by Fourier-transform infrared spectrometry. To distinguish the bands due to the cationic amine ion from the acetate anion ones, a molecular decyletheramine was also studied, as well as its salts, after some degrees of neutralisation, by acetic or hydrochloric acids; also, potassium acetate was included, to assess the anion bands alone. From this approach, all the significant bands were successfully assigned to the important functional groups in the collector’s molecule: NHx, CH2, CH3, –O–, and the acetate bands. A confirmation of this method was the identification of the amine cation bands alone, without the presence of the previously associated acetate bands, after adsorption onto the surface of quartz particles, from an aqueous solution of a decyletheramine acetate, at pH = 10.5.