The mechanism of selective wolframite flotation using amidoxime collectors: A combined DFT calculation and experimental study

This study investigates the mechanism of novel amidoxime-based collectors ——4-pyridylamidoxime (PA), 3-ethyl-4-pyridylamidoxime (EPA), and 3-methyl-5-tert-butyl-4-pyridylamidoxime (MBPA) in the flotation separation of wolframite from gangue minerals (calcite and quartz). Through a combination of theoretical simulations with flotation experiments, the structure-activity relationship and selective adsorption mechanism of these collectors are systematically revealed. The results indicate that the ionic form of collectors exhibit higher reactivity, with MBPA demonstrating the most favorable electron-donating capacity and its molecular electrostatic potential of −0.223 eV. Density functional theory (DFT) calculations indicate that MBPA forms strong covalent bond-dominated adsorption on wolframite (0 2 0) surface, medium-strength polar covalent adsorption on quartz (1 0 1) surface, and must overcome a significant adsorption energy barrier on calcite (1 0 4) surface. This comprehensively explains the selectivity order (wolframite > quartz > calcite) at the mechanistic level. Flotation experiments demonstrate that MBPA achieved a high wolframite recovery of 86.77 % without the need for activators, significantly higher than that of calcite (16.51 %) and quartz (27.11 %). FT-IR spectroscopy further confirmed its chemical adsorption on wolframite surfaces. This study provides an efficient collector for wolframite flotation and offers theoretical insights and new strategies for flotation reagents design.