Abstract: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.

Key words: surface dissolution; flotation; kinetic parameters; modified rate constant; selectivity index; collector adsorption