Interfacial adsorption mechanism of a polyamine/fatty acid combined collector for selective flotation separation of quartz and feldspar

The flotation separation behavior and interfacial adsorption mechanism of quartz and albite regulated by a combined collector (DN12/NaOL) were systematically investigated through micro-flotation experiments, comprehensive interfacial characterization, and density functional theory calculations. At pH = 4, a combined collector concentration of 3.5 × 10 -4 mol/L and a DN12/NaOL molar ratio of 1:1 produced a albite–quartz recovery difference of 56.76%. For artificial mixture, the albite recovery reached 87.78%. Compared with the individual collectors, the combined collector exhibited a lower critical micelle concentration and surface tension, denser interfacial packing, and favorable intermolecular association. After the interaction of DN12/NaOL with albite and quartz, albite exhibited more pronounced changes in surface properties. Besides, the adsorption energy of DN12/NaOL on the albite surface was higher than that on the quartz surface, and the selectivity originated from the coupling of electrostatic attraction and hydrogen bonding between DN12 and mineral surface, specific coordination between oleate carboxylate groups and exposed Al 3+ sites on albite, and hydrophobic association between alkyl chains. These interactions promoted the formation of a compact and stable hydrophobic adsorption layer on albite while leaving quartz comparatively weakly modified, thereby enabling selective flotation separation. The results provided a theoretical basis for the efficient purification of high-purity quartz ore.