Uncovering the mechanism of the combined collectors DDA + SDS on the flotation separation of lepidolite from albite and quartz through the AFM force

DDA + SDS with molar ratio of 3:7 could efficiently separate lepidolite from albite and quartz at pH ∼ 8.0. • The adsorption mechanisms of DDA + SDS on lepidolite, albite and quartz were unraveled by AFM force measurement. • DDA + SDS adsorbed on lepidolite surface by the hydrophobic and electrostatic attractions. • DDA + SDS adsorbed on albite and quartz surfaces by the electrostatic attraction. This study investigated the underlying flotation mechanism for separating lepidolite from lepidolite-albite-quartz mixture via the combined collectors of dodecylamine (DDA) and sodium dodecyl sulfate (SDS). The micro-flotation results exhibited that DDA + SDS could efficiently separate lepidolite from their mixture without depressant. At pH ∼ 8.0 and the molar ratio of DDA: SDS = 3:7, DDA + SDS with the total dose of 2.0 × 10 -4 mol/L achieved 85.05% Li 2 O recovery with Li 2 O grade of 4.07% from the artificial mixture of the three minerals with the mass ratio of 1:1:1. The results of contact angle, adsorption capacity, zeta potential, optical microscope image, FTIR, in-situ AFM image demonstrated that DDA could adsorb on lepidolite, albite and quartz surfaces and render them hydrophobic. The presence of SDS slightly affected DDA’s adsorption onto the lepidolite surface, while significantly inhibited DDA’s adsorption on the albite and quartz surfaces. AFM force measurements implied that the hydrophobic attraction existed between lepidolite’s Si-O tetrahedra and the carbon chain of DDA + SDS, while that was absent in albite and quartz surfaces. Thus, DDA + SDS could adsorb on lepidolite surface via hydrophobic and electrostatic attraction. While, it only exhibited the weakly electrostatic attraction to albite and quartz surfaces, thereby hardly adsorbing on their surfaces and rendering them hydrophobic. The different adsorption configurations of DDA + SDS on lepidolite, albite and quartz caused the different wettability and floatability, promoting the selective separation of lepidolite from their mixture. The adsorption mechanism of DDA+SDS on lepidolite, albite and quartz surfaces. Download: Download high-res image (183KB) Download: Download full-size image