The role of gellan gum in the selective flotation separation of fluorite from calcite: An experimental and molecular dynamics simulation study

Abstract

Fluorite as the main source of fluorine generally coexists with calcite. The highly similar floatabilities and physicochemical properties make it tough to separate these two minerals. Herein, gellan gum (GG) was used as depressant to separate fluorite from calcite for the first time. Several experiments and tests were utilized to explain the inhibiting performance and mechanism of GG. Flotation experiments illustrated that GG displayed an outstanding depression performance for the calcite flotation, whereas it hardly depressed fluorite. Zeta potential analyses, surfaces wettability measurements and Fourier transform infrared (FTIR) indicated that GG strongly adhered onto calcite and prevented the NaOL from adhering on it. Adsorption amount measurements indicated that the GG adhered onto calcite with a higher amount compared to fluorite. X-ray photoelectron spectroscopy (XPS) tests pointed out that GG adsorbed onto calcite and fluorite surfaces by strong chemisorption and weak physisorption, respectively. Atomic force microscopy (AFM) measurements implied visually that GG adsorbed denser and stronger on the calcite than fluorite. Molecular dynamics (MD) simulations demonstrated that compared with fluorite, more GG adsorbed on the calcite surface due to the reaction between hydroxyl groups and the mineral surface, as evidenced by higher diffusion coefficient for water (Dwater) value, smaller interaction distance, and higher relative concentration of GG on the calcite surface. Therefore, GG could be employed as a promising flotation depressant in separating fluorite from calcite.