Impact of ethanol on the flotation efficiency of imidazolium ionic liquids as collectors: Insights from dynamic surface tension and solvation analysis

Abstract

To conduct extensive research on the application of ionic liquids as collectors in mineral flotation, ethanol (EtOH) was used as a solvent to dissolve hydrophobic ionic liquids (ILs) to simplify the reagent regime. Interesting phenomena were observed in which EtOH exerted 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 as a collector for pure quartz flotation tests at a concentration of 1 × 10⁻⁵ mol·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% under the same conditions. The conditional experiments under 1 × 10⁻⁵ mol·L⁻¹ ILs for EtOH concentration and under 2vol% EtOH for ILs concentration confirmed this difference. 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 the C₁₂[mim]Cl collector, whereas the hematite concentrate grade and recovery for the C₁₂[mim]PF₆ collector increased. On the basis of these differences and observations of flotation foam, two-phase bubble observation tests were carried out. The EtOH promoted the foam height of two ILs during aeration. It accelerated static froth defoaming after aeration stopped, and the foam of C₁₂[mim]PF₆ defoaming especially quickly. In the discussion of flotation tests and foam observation, an attempt was made to explain the reasons and mechanisms behind the diverse phenomena using the dynamic surface tension effect and solvation effect results from EtOH. The solvation effect was verified through Fourier transform infrared (FT-IR), X-ray photoelectron spectroscopy (XPS), and Zeta potential tests. Although EtOH affects the adsorption of ILs on the ore surface during flotation negatively, it holds an positive value of inhibiting foam merging during flotation aeration and accelerating the defoaming of static foam. And induce more robust secondary enrichment in the mixed ore flotation of the C₁₂[mim]PF₆ collector, facilitating effective mixed ore separation even under inhibitor-free conditions.

Keywords

ionic liquid / ethanol / flotation foam / solvation / dynamic surface tension

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