Flotation separation of fluorite and calcite using anhydrous glucose and aluminum sulfate as a combined depressant

The effective flotation separation of fluorite and calcite is a critical problem in the mineral processing industry owing to their similar physicochemical characteristics. In this study, the effect of glucose (Glu) and Al3+ on the flotation separation of fluorite and calcite was studied using micro-flotation experiments, scanning electron microscopy (SEM), solution chemistry calculation, X-ray photoelectron spectroscopy (XPS), and density functional theory (DFT). The micro-flotation experiments demonstrate that the combination of Glu and Al3+ had a significant depression effect on calcite. However, it slightly affected fluorite flotation. The SEM results indicate that Glu and Al3+ had a greater tendency of absorption on the calcite surface than that of fluorite. The solution chemistry calculation and XPS analysis exhibit that the increased selective depression of Glu on calcite with the addition of Al3+ was due to the formation of Al (OH) 3 and Al2O3 on the calcite surface. The DFT results exhibit that Ca-O bonds were formed when Glu interacted with fluorite. Additionally, Ca-O, C–H, and H-O bonds were formed when Glu interacted with the surface of calcite. The surface bonding characteristics of Glu with fluorite and calcite led to a difference in the adsorption energy. The glucose and Al2O3 glucose formed on the surface of calcite improved the adsorption through Al-O bond, which increased the adsorption sites on the surface of calcite and enhanced the depression effect of Glu on calcite.