Selective flotation of ilmenite from diopside using 8-hydroxyquinoline: An FeN-dominated adsorption mechanism
Year: 2026
Type: article
Abstract: Selective flotation separation of ilmenite from calcium–magnesium silicate gangue remains challenging because of the weak natural hydrophobicity of ilmenite and the insufficient selectivity of conventional collectors. In this study, 8-hydroxyquinoline (8-HQ), a heterocyclic N,O-donor reagent, was evaluated as a selective collector for ilmenite–diopside separation. At pH 7.0 ± 0.2 and an 8-HQ concentration of 1.0 × 1 0 − 4 mol L −1 , the single-mineral recoveries of ilmenite and diopside were 90.1% and 25.0%, respectively. Artificially mixed-mineral flotation under the selected conditions yielded a concentrate containing 43.8% TiO 2 at a recovery of 86.7%, demonstrating effective separation of ilmenite from diopside. After 8-HQ treatment, the contact angle of ilmenite increased from 42.1° to 78.2°, whereas that of diopside increased only from 27.2° to 35.8°. UV–vis analysis showed that the adsorption amount of 8-HQ on ilmenite reached 0.138 mg g −1 , approximately 3.6 times that on diopside. The appearance of an N 1s signal and slight but consistent changes in the Fe 2p and O 1s spectra further supported preferential adsorption on ilmenite. Spin-polarized PBE+ U +TS calculations yielded an adsorption energy of approximately −1.66 eV and optimized Fe N and Fe O distances of 2.14 and 2.48 Å, respectively. Partial overlap between the surface Fe 3d and 8-HQ N 2p states further supported an Fe N-dominated adsorption interaction, with the hydroxyl O group providing an auxiliary contribution. These results show that selective adsorption of 8-HQ on exposed Fe sites enhances ilmenite hydrophobicity and enables its effective flotation separation from diopside. • 8-HQ selectively separates ilmenite from diopside at neutral pH. • Mixed-mineral flotation yields 43.8% TiO 2 at 86.7% recovery. • 8-HQ adsorption on ilmenite is 3.6 times that on diopside. • XPS and DFT reveal Fe N-dominated adsorption on ilmenite. • Auxiliary Fe O interaction further stabilizes 8-HQ adsorption.
Source: Minerals Engineering
Language: English
Subfield: Water Science and Technology
Field: Environmental Science
Domain: Physical Sciences
Open Access status: hybrid
Estimated APC paid: $4,220
OpenAlex ID: W7222790634