Flotation properties and separation mechanism of ammonium dodecylsulfate on lepidolite minerals

Abstract

Lepidolite, feldspar, and quartz are silicate minerals with similar chemical properties, complicating their flotation separation. Current collector systems require strong acidic conditions for effective separation but still face challenges related to low separation efficiency and recovery rates. This study proposed a novel collector, ammonium dodecylsulfate (ALS), to selectively extract lepidolite from feldspar and quartz using highly selective flotation methods. Microflotation experiments showed that ALS significantly outperforms other collectors in collecting lepidolite compared to feldspar and quartz. At pH 7, lepidolite recovery reached 95%, while flotation recoveries for both feldspar and quartz were below 10%. Mixed pure mineral flotation tests revealed that at pH 7 and ALS concentration of 2.5 × 10^–4 mol·L⁻¹, the Li₂O content in the concentrate was 4.21%, with a recovery rate of 95.01%. Separation efficiency and Gaudin selectivity index values were recorded. Solution chemical analyses showed that at pH 7, ALS completely ionizes into NH₄⁺ and CH₃(CH₂)₁₁OSO₃⁻. Various analytical techniques, including high-speed photography imaging, contact angle measurements, Fourier transform infrared spectroscopy, zeta potential analysis, and X-ray photoelectron spectroscopy, confirmed that the anion CH₃(CH₂)₁₁OSO₃⁻ adsorbs chemically onto aluminum sites on lepidolite's surface, while the cation NH₄⁺ binds through electrostatic interactions and hydrogen bonding. The combined adsorption of these ions on lepidolite's surface enhanced its hydrophobicity. In contrast, ALS showed minimal adsorption on feldspar and quartz surfaces, which remained hydrophilic, enabling efficient selective flotation separation of lepidolite from both feldspar and quartz.

Graphical abstract