Experimental and molecular dynamics simulation study on the flotation separation of fluorite from calcite with tara gum as depressant

Fluorite commonly coexists with calcite, whilst the separation of these two minerals is a longstanding challenge due to their closely similar surface properties. In this work, froth flotation was adopted to remove calcite from fluorite with tara gum (TG) innovatively performed as the calcite depressant. Flotation experiment results showed that TG exhibited strong depression performance for calcite in a broad pH range (6–8) in sodium oleate (NaOL) system. Zeta potential results confirmed that TG trended to selectively react on the calcite and prevented the function of NaOL onto calcite surface. X-ray photoelectron spectroscopy (XPS) measurement found that TG chemisorbed onto calcite, while physically adsorbed on the fluorite. Atomic force microscopy (AFM) tests indicated that TG densely adhered onto calcite surface and greatly enhanced its hydrophilicity, whereas it adsorbed weakly on the fluorite surface. Molecular dynamics (MD) simulations further concluded that TG could abundantly adhere to the calcite surface with higher intensity and capacity. Therefore, TG exhibited effective depression impact on calcite and achieved the separation of fluorite from calcite successfully.