Selective lepidolite–quartz flotation using an environmentally benign collector dodecylbenzenesulfonate isopropanolamine activated by Ca2+

Abstract

Efficient separation of quartz from low-grade lepidolite ores by flotation remains difficult because the two minerals share similar surface chemistry. In the present work, dodecylbenzenesulfonate isopropanolamine (LAS) was introduced as an environmentally benign collector, with Ca 2+ as an activator, to selectively float lepidolite from quartz. Micro-flotation tests showed that at natural pH, with Ca 2+ and LAS concentrations of 1.5 × 10 −4 mol/L and 2 × 10 −4 mol/L respectively, the processing of artificially mixed minerals yielded a Li 2 O concentrate assaying 5.03% at a recovery of 87.85%. Contact angle measurements, zeta potential analysis, and Fourier transform infrared spectroscopy (FTIR) confirmed that LAS adsorbs onto the Ca 2+ -activated lepidolite surface through electrostatic attraction, markedly raising its hydrophobicity. X-ray photoelectron spectroscopy (XPS) and density functional theory (DFT) calculations further revealed that Ca 2+ acts as a bridging medium: it anchors to surface lattice oxygen of lepidolite by electrostatic forces while coordinating with the −SO 3 − group of LAS through strong inner-sphere binding. Under this bridging configuration, the long hydrophobic alkyl chains of LAS orient outward from the mineral surface and assemble into a compact hydrophobic layer, thereby strengthening lepidolite hydrophobicity and improving its floatability. These findings indicate that the LAS/Ca 2+ reagent scheme holds strong promise for efficient lepidolite-quartz separation.