Flotation separation of feldspar from quartz using NaOL and TTPC as a combined collector

Quartz and feldspar, both framework silicates, exhibit remarkably similar physicochemical properties, rendering their efficient flotation separation a persistent challenge in mineral processing. Conventional collector systems typically require strongly acidic conditions for effective separation yet still suffer from suboptimal concentrate grades or recoveries. To mitigate water contamination from acidic wastewater discharge and achieve highly selective flotation separation of quartz and feldspar, this study introduces a novel collector combination—tributyl tetradecyl phosphonium chloride (TTPC) and sodium oleate (NaOL). This system enables selective surface modification of the minerals under neutral pH conditions, thereby accomplishing highly efficient separation. Micro-flotation and artificial mixed ore tests demonstrate TTPC's superior affinity for quartz over feldspar, with NaOL further optimizing separation performance. Floation of artificially mixed ore (initial grades: 82.70 % SiO₂, 10.71 % Al₂O₃) yielded exceptional results: a concentrate grading 98.77 % SiO₂ at 51.80 % recovery, alongside tailings assaying 18.61 % Al₂O₃ with 98.42 % recovery. Mechanistic investigations utilizing a multimodal approach—including high-speed imaging, contact angle measurements, Fourier transform infrared (FTIR) spectroscopy, zeta potential analysis, and X-ray photoelectron spectroscopy (XPS)—elucidated the selective adsorption behavior. Under single-reagent conditions, NaOL shows negligible adsorption on either mineral, while TTPC undergoes electrostatic adsorption on both. During co-treatment, synergistic adsorption of TTPC and NaOL occurs exclusively on quartz, enhancing its floatability. Conversely, NaOL impedes TTPC adsorption on feldspar, maintaining its hydrophilicity. This amplified flotation response differential enables highly selective separation. A conceptual model elucidating the selective adsorption mechanisms on both mineral surfaces is proposed.