Efficient separation of cassiterite from quartz using a bis(2-ethylhexyl) phosphate collector

Bis(2-ethylhexyl) phosphate (HDEHP) was introduced as a novel collector for the flotation separation of cassiterite from quartz. Under the optimized flotation conditions (pH 8.0±0.2, HDEHP concentration of 15.0×10 -5 mol/L), a cassiterite concentrate assaying 74.01% SnO 2 was obtained with a recovery of 94.63%, demonstrating excellent separation performance. Compared with benzohydroxamic acid (BHA), HDEHP exhibited superior selectivity over a broader pH range. The adsorption mechanism was systematically investigated through contact angle measurements, zeta potential analysis, FTIR, XPS, ToF‑SIMS, AFM, and DFT calculations. The results indicate that HDEHP chemisorbs onto the cassiterite surface primarily via its PO(OH) groups, which coordinate with surface Sn sites to form a stable hydrophobic layer. In contrast, its interaction with quartz remained weak. DFT simulations further revealed that electron transfer and orbital hybridization occur between the oxygen atoms of HDEHP and surface Sn atoms, leading to stable chemical bonding and enhanced adsorption. Consequently, due to its strong and selective adsorption on cassiterite, HDEHP serves as an effective collector for the flotation separation of cassiterite from quartz.