Selective adsorption and surface wettability modulation of quartz by amide-based gemini collector GS-A6 for efficient apatite–quartz reverse flotation

The flotation removal of silica impurities from phosphate ore is a prerequisite for its subsequent processing and utilization. However, current cationic collectors used for silica removal in phosphate ore flotation suffer from low selectivity, hindering efficient apatite-quartz separation. This study investigated the efficient separation of quartz and apatite using amide-based gemini quaternary ammonium salt GS-A6 as a high-efficiency collector in reverse flotation. Through systematic flotation investigations and characterization analyses, the separation performance of GS-A6 was evaluated, and its adsorption behavior on mineral surfaces was elucidated. Flotation results indicate that under pH 7.0 and 3.0 mg/L GS-A6, a recovery of 94.68% apatite concentrate, P 2 O 5 grade of 39.98%, and separation efficiency of 91.51% was achieved, facilitating efficient separation of apatite from quartz. Surface wettability and SEM-EDS measurements indicate that GS-A6 strongly adsorbs onto quartz surfaces rather than apatite, selectively enhancing quartz surface hydrophobicity and thereby achieving excellent floatability of quartz. Zeta potential, FT-IR, and XPS analyses reveal that GS-A6′s strong adsorption on quartz surfaces stems from intense electrostatic attraction between its cations and negatively charged quartz surfaces, coupled with hydrogen bonding between the −C=O and N–H groups of the amide moiety in GS-A6 molecules and quartz surfaces. Consequently, GS-A6 functions as an efficient quartz collector in the purification of siliceous phosphate ores through reverse flotation.