Stereoelectric masking of calcite by a chain-type AA/AMPS polymer for precise flotation of scheelite

The flotation separation of calcium-bearing minerals remains challenging due to their similar crystal structures and calcium active sites. Conventional depressants like sodium silicate are required in large dosages, leading to significant issues with wastewater treatment and economic viability. Herein, a novel depressant scheme combining poly(acrylic acid-2-acrylamido-2-methylpropane sulfonic acid) (AA/AMPS) and sodium oleate (NaOl) was employed for flotation separation of calcite from scheelite. The underlying mechanism was elucidated through surface analysis and density functional theory (DFT) calculations. The results demonstrate that at a pulp pH of 8.0 and with a low AA/AMPS dosage of merely 4 × 10 −6 mg/L, a scheelite concentrate with a WO 3 grade of 69.8% was obtained from the artificial mixed ore. This concentrate exhibited superior grade and recovery compared to those achieved using traditional sodium silicate and other reported novel depressants, while requiring a significantly lower reagent dosage. The study confirms that the –SO 3 − groups in AA/AMPS engage in strong, specific chemisorption with the active sites on the calcite surface via an electronic effect. The pronounced differences in adsorption thermodynamics and electrostatic repulsion enable AA/AMPS to achieve highly selective masking of the active sites on calcite. Consequently, this research presents an efficient depressant for the scheelite separation. These findings indicate that AA/AMPS is an efficient and environmentally benign depressant, demonstrating promising potential for industrial scheelite flotation.