Probing the interfacial role of hydrolysed polymaleic anhydride for efficient target adsorption in scheelite-calcite flotation system: experimental application and atomic-scale mechanisms

Tungsten, a strategic non-ferrous metal critical for advanced industrial applications, predominantly exists as underutilized scheelite resources characterized by fine-grained intergrowths with calcite that are challenging to separate. This study deciphers the atomic-scale mechanism underlying the selective flotation separation of scheelite from calcite mediated by hydrolyzed polymaleic anhydride (HPMA), a novel environmentally benign reagent, through integrated experimental characterization and computational simulations. Micro–flotation assays quantitatively demonstrated HPMA’s exceptional selectivity, suppressing calcite recovery from 91.64% to 18.61% at pH 7 (10 mg/L dosage) while preserving scheelite floatability. FTIR spectroscopy revealed HPMA preferentially adsorbs on calcite, efficiently hindering sodium oleate (NaOL) attachment, whereas NaOL selectively binds to scheelite. XPS analysis confirmed carboxyl (–COO-) group chemisorption at calcite’s Ca sites, evidenced by a 0.26 eV negative shift in Ca 2p3/2 binding energy and new Ca-O bond formation. Density functional theory (DFT) simulations quantified adsorption energetics: HPMA exhibited stronger affinity for calcite (104) surfaces (-278.8 kcal/mol) versus scheelite (112) (-80.1 kcal/mol). Mulliken bond population analysis quantified interfacial bonding nature. The calcite–HPMA interface formed polar covalent bonds (populations 0.23-0.28), contrasting with NaOL’s ionic interactions (population 0.13) on scheelite. This covalent advantage enables HPMA to preferentially passivate calcite surfaces, suppressing NaOL co-adsorption and facilitating selective scheelite recovery through differential surface reactivity modulation.