Effect of surface dissolution on kinetic parameters in flotation of ilmenite from different gangue minerals

The effects of acid surface dissolution on the flotation kinetics of ilmenite (IL) and its common accompanied gangue minerals including olivine-pyroxene (Ol-Px), tremolite-clinochlore (Tr-Cch) and quartz were investigated. The results show that through the surface dissolution the adsorption rate constant for ilmenite increases from 5.272 to 8.441 mol/(g.min) while it decreases for Ol-Px, Tr-Cch and quartz from 6.332, 7.309 and 7.774 mol/(g.min) to 5.034, 6.223 and 7.371 mol/(g.min), respectively. Also, the flotation experiments on a binary mixture of minerals indicate that after surface dissolution the values of modified rate constant for ilmenite flotation from Ol-Px, Tr-Cch and quartz are enhanced from 36.15, 36.52 and 47.86 min(-1) to 41.72, 45.78 and 56.24 min(-1), respectively. This results in the improvement of kinetic selectivity index (SI) in the separation of treated ilmenite from gangue minerals. As evidenced by ICP-MS analysis, the decrease of kinetic parameters for gangue minerals can be due to the removal of Fe2+, Ca2+ and Mg2+ ions from their surfaces, which results in the lack of enough active sites to interact with collector species. As confirmed by contact angle measurements, this prevents the formation of a stable hydrophobic layer on the minerals surfaces for creating stable attachments between minerals and bubbles. Generally, the improvement of ilmenite flotation kinetics has a negative correlation with the iron content in its accompanied gangue minerals.