Effect of Fe³⁺ on the Activation of Fluorite and Its Flotation Separation from Calcite in Floating Scheelite Tailings

In the flotation of scheelite, fluorite and calcite, the addition of inhibitors often increases the difficulty of the subsequent flotation separation of fluorite and calcite. The activation effect of Fe³⁺ on suppressed fluorite in floating scheelite tailings and its effect on flotation separation from calcite were studied through flotation test, adsorption capacity test, Zeta potential measurement and solution chemical calculation. The results of single mineral flotation test showed that the inhibition effect of Fe³⁺ on calcite was much greater than that of fluorite. When water glass was added separately, two minerals were inhibited simultaneously. Under the conditions of pH 8.0, 300 mg/L sodium silicate and 1.5×10⁻⁴ mol/L sodium oleate, the recovery rates of fluorite and calcite were 13.49% and 16.83%, respectively. When Fe³⁺ was introduced into the water glass system, Under the conditions of pH 8.0, 75 mg/L sodium silicate, 3×10⁻⁴ mol/L Fe³⁺ and 1.5×10⁻⁴ mol/L sodium oleate, the flotation recovery rates of fluorite and calcite were 82.01% and 15.64%, respectively. The addition of Fe³⁺ can improve the floatability of suppressed fluorite and selectively activate fluorite in water glass system. The mechanism analysis showed that Fe³⁺ was more likely to adsorb on the surface of calcite, which hindered the adsorption of sodium oleate. The hydrolyzed components Fe(OH)₂⁺ and Fe(OH)₄⁻ of Fe³⁺ in solution selectively reacted with the hydrolyzed components Si(OH)₄ and SiO(OH)₃⁻ of water glass on fluorite surface to form Fe⁺− water glass polymer after adding Fe³⁺ to water glass system. The hydrolyzed components of water glass on the surface of fluorite were reduced, and the floatability of fluorite was restored. However, Fe⁺− water glass polymer were more adsorbed on the surface of calcite, which further inhibited the flotation of calcite.