Selective flotation of silicates from phosphates using Tetrabutyl Ammonium Chloride as a green collector

This study introduces Tetrabutyl Ammonium Chloride (TBAC) as a novel selective collector for silicates in the reverse flotation of apatite-quartz model sample. Zeta potential measurements, contact angle analysis, FTIR, and X-ray fluorescence spectroscopy (XPS) were employed to investigate reagent adsorption at mineral-water interfaces. FTIR analysis revealed the appearance of new peaks corresponding to C–H and C–N stretching in TBAC-treated quartz, but not in apatite, indicating TBAC's preferential adsorption on quartz surfaces. XPS analysis further supported FTIR results; a distinct N 1s peak at 401.5 eV was observed on TBAC-treated quartz, while no such peak appeared on apatite, confirming the absence of significant interaction. Zeta potential measurements showed a larger shift in surface charge for quartz than for apatite after TBAC treatment, particularly at higher pH levels, with a notable shift of +16.28 mV at pH 11 for quartz, compared to only +0.4 mV for apatite. Contact angle measurements also demonstrated that TBAC significantly increased quartz hydrophobicity—reaching values above 115°—while apatite showed minimal change. Flotation tests were conducted to evaluate the performance of TBAC as collector for apatite and quartz. In single mineral flotation, the highest quartz recovery (97 %) was achieved at pH 11 with a TBAC dosage of 150 g/ton while the apatite recovery was reduced to 31.6 %. The binary-mineral system showed a higher recovery of apatite with a commercial quartz collector at 52.4 %, compared to just 25.3 % when TBAC was used. Comparative tests with a conventional DA collector revealed that apatite recovery was significantly higher with DA (52.4 %) than with TBAC (25.3 %), emphasizing TBAC's limited interaction with phosphate minerals and its potential utility for silicate removal in reverse flotation processes.