Fluorite flotation separation from calcite using guar gum as a depressant

• Guar gum enables selective fluorite-calcite separation by flotation. • Guar gum masks calcite hydrophilically, blocking collector adsorption. • Multi-technique analysis reveals the differential adsorption mechanism. • DFT simulations provide atomic-scale insight into the selectivity. As a strategically significant non-metallic mineral resource, fluorite faces considerable challenges in its flotation separation from associated calcite due to their highly similar surface properties and nearly identical responses to conventional reagents. Traditional depressants not only demonstrate inadequate selectivity in distinguishing these calcium-containing minerals but also raise environmental concerns. This study introduces guar gum (GG), a natural polysaccharide derived from renewable plant sources, as a highly selective depressant for calcite in fluorite flotation using sodium oleate (NaOL) as the collector. Systematic flotation tests revealed that GG strongly depresses calcite flotation while minimally affecting fluorite floatability. At an optimized concentration of 25 mg/L GG, calcite recovery drastically decreased to only 2.5 %, while fluorite recovery remained at approximately 85 %, demonstrating exceptional selectivity. Artificial mixed-ore flotation tests under carefully optimized conditions successfully upgraded the CaF 2 grade from 49.72 % to 79.48 % with a fluorite recovery of 92.25 %, confirming practical separation efficiency. Surface analysis through multiple characterization techniques verified that GG selectively adsorbs on calcite surfaces, rendering them hydrophilic and effectively blocking subsequent NaOL adsorption. Fourier transform infrared spectroscopy and density functional theory simulations provided crucial molecular-level insights, consistently revealing GG's significantly stronger adsorption affinity and more favorable interaction energy with calcite compared to fluorite. These fundamental findings offer a comprehensive molecular-level explanation for the observed differential flotation behavior. This research validates GG as an efficient, highly selective, and environmentally friendly depressant that enables effective separation of fluorite from calcite, providing a sustainable alternative to conventional reagents in mineral processing operations.