Inhibition mechanism of highly selective flotation separation of scheelite and calcite by novel complexes: based on the undirected coordination of rare earth ions

Developed a new Er-CMC reagent for flotation separation of scheelite and calcite. • The WO 3 grade of the optimal system is 73.14%, with a recovery rate of 96%. • The influence of complex stability on flotation was investigated using automatic potentiometric titration and quantum chemical calculations. • The non directional coordination of Er ions adapts to the undulating surface of calcite (104) and can tightly adhere to form a stable irregular pentahedral structure. Scheelite and calcite share analogous surface characteristics, hindering their flotation separation, while traditional depressants suffer from excessive dosage and poor selectivity. This work fabricates a stable, high-selectivity composite depressant consisting of lanthanide Er 3+ and macromolecular CMC for effective scheelite-calcite separation. At a depressant dosage of 1 mg/L and an Er 3+ to CMC ratio of 1:2, this composite depressant elevated the scheelite concentrate grade to 73.12%. Potentiometric titration, density functional theory (DFT) calculations and FTIR spectroscopy were adopted to reveal the underlying mechanism. Er 3+ can bind to the long carbon chains of CMC at arbitrary angles to form stable complexes. Subsequently, irregular pentahedral coordination structures are constructed via interactions between Er 3+ and oxygen atoms in CO 3 2− . These complexes tightly attach to the calcite surface and generate a hydrophilic film, thereby blocking the adsorption of collectors. This coordination flotation strategy highlights lanthanides’ unique mineral processing merits and guides novel flotation reagent development. Download: Download high-res image (167KB) Download: Download full-size image