Active Mechanisms in the Flotation of Hematite with Fatty, Acids and Amines

The effect of hydrogen chain length in the fatty flotation of oxides, in particular hematite, has been studied. Flotation of hematite was not promoted when acetic and caprice (6 C) acids were used as collectors even though chemisorption of these acids on the mineral surface was observed using infrared spectroscopy. Flotation response was initiated with caprylic (8C) acid with recovery successively increasing with increasing chain length. Hydrocarbon chain association at the mineral-collector interface after collector chemisorption was determined to be operative in the promotion of flotation. A value of 1.1. kT per -CH2- group, or approximately 0.6 kcal/mole of 0CH2- groups removed from aqueous environment, was calculated from flotation collector concentrations versus hydrocarbon chain length data. The The value of 1.1 kT per -CH2- group was found to be in agreement with the van der Waals cohesive free energy of 1.0 kT per -CH2- groups as required in the hemimicelle theory. It appears that the aminiumion, RNH3+, is the active species in amine flotation of oxides. Flotation is effeted above the zpc when the aminiumion to hydrogen ratio is approximately 1000:1. Increasing the chain length of the amine reduces this reatio because of the lower bulk concentration collector needed to associate chains. Flotation response with amines is reduced at high pH values because of the hydrolysis of aminiumion to aqueous amine hydroxide. Aminiumion at such low concentrations cannot compete for sureface sites with such species as K+ or Na+ added as the hydroxide for pH adjustment.

- 800 600 4 activated b, c caproic ac id outgassed adsorbed e at pH 9. II in the presence of various saturated fatty acids 9 1200 cid at pH 5.0 10 1000 12 800 20 15 600 40 E conditioned KOI at 3 pH 8.5 minutes In 1x10-3 M TITE condit ioned KOI at 3 pH 6.0 minutes in 1x 10-3 M 9 10 1000 x10-3 KOI at pH 2.0 M 12 800 20 15 600 4