Examining the Impact of Ethanol on Flotation Efficiency of Imidazolium Ionic Liquids as Collectors: Insights from Dynamic Surface Tension and Solvation Analysis

In order to conduct more extensive research on the application of ionic liquids (ILs) as collectors in minerals flotation, ethanol (EtOH) was used as a solvent to dissolve hydrophobic ILs to simplify the reagent regime. Some interesting phenomena were observed that EtOH caused different effects on the flotation efficiency of two ILs with similar structures. When EtOH was used to dissolve 1-Dodecyl-3-methylimidazolium chloride (C12[mim]Cl), and C12[mim]Cl as collector for pure quartz flotation tests at the concentration of 1*10-5mol*L-1, quartz recovery increased from 23.77% to 77.91% compared with ILs dissolved in water. However, quartz recovery of 1-Dodecyl-3-methylimidazolium hexafluorophosphate (C12[mim]PF6) decreased from 60.45% to 24.52% in the same cases. the EtOH concentration tests under 1*10-5mol*L-1 ILs and the ILs concentration tests under 2% EtOH confirmed this. After being affected by EtOH, the mixed ore flotation tests of quartz and hematite showed a decrease in the hematite concentrate grade and recovery for C12[mim]Cl collector, while the hematite concentrate grade and recovery for C12[mim]PF6 collector both increased. Based on these interesting differences and observation in flotation tests, the two-phase bubble observation tests were carried out and it showed that EtOH promoted foam height of two ILs during aeration but accelerated static froth defoaming after aeration stopped, and the foam of C12[mim]PF6 defoaming more quickly. Through the discussion of flotation tests and foam observation, an attempt was made to explain the reasons and mechanisms of various differences phenomenon using the dynamic surface tension effect and solvation effect result from EtOH. The solvation effect was verified by IR, XPS and Zeta potential tests. It can be assumed that although EtOH has a negative effect on the adsorption of ILs on the ore surface during the flotation process, it has application reference value for the inhibition of foam merging during the flotation aeration process and the acceleration of the defoaming of static foam. These effects induced a stronger secondary enrichment in the mixed ore flotation of C12[mim]PF6 collector, so that C12[mim]PF6 obtained good mixed ore separation under the condition of no any inhibitor.