Mechanism of flotation separation of scheelite from calcite using sulfonated phenolic resin as a novel depressant

To address the challenge of separating scheelite and calcite due to their similar physicochemical properties, this study employed sulfonated phenolic resin (SPR) as a depressant and evaluated its impacts on the flotation behavior of scheelite and calcite in the system with sodium oleate (NaOL) as a collector. The mechanism of SPR on scheelite and calcite surfaces was investigated by contact angle measurements, Zeta potential analysis, infrared spectroscopy, X-ray photoelectron spectroscopy and density functional theory simulations. The results demonstrated that scheelite and calcite could be effectively separated with a significant recovery difference of 51.33 % under conditions of 60.0 mg/L SPR at pH 9.5. Mechanism studies revealed SPR was adsorbed on the mineral surface through the interaction between the oxygen atoms in the sulfonic acid group and calcium ions. Moreover, SPR was more strongly adsorbed on calcite, with an adsorption energy of −81.05 kJ/mol on calcite, while the adsorption energy on scheelite was −57.89 kJ/mol. Consequently, SPR occupied more calcium adsorption sites on the calcite surface, significantly hindering the subsequent adsorption of NaOL on calcite, while causing minimal interference with NaOL adsorption on scheelite. This differential adsorption behavior enhanced the floatability contrast between the two minerals, thereby achieving the selective flotation separation of scheelite from calcite.