The floatability of fluorite and calcite exhibit similar properties, rendering their flotation separation challenging. Macromolecular polysaccharide reagents containing the polyhydroxyl group have shown broad promising application. The selectivity of polysaccharide is relatively low. In this study, the introduction of Fe³⁺ was employed to enhance the selective adsorption capacity of Pullulan polysaccharide towards fluorite and calcite minerals, thereby achieving effective flotation separation. Furthermore, the mechanism underlying intramolecular interactions was elucidated. The DFT calculation and XPS analysis revealed that the adsorption of Fe³⁺ on the calcite surface was more favorable, leading to the formation of a Ca-O-Fe structure. The MD simulation, XPS analysis, and Zeta potential analysis revealed that the Fe-OH groups on the surface of calcite reacted with the -OH groups in Pullulan and formed bonds, resulting in the formation of a Calcite-Fe-Pullulan structure. This facilitated the attachment of a significant number of Pullulan molecules to the calcite surface. The formation of a hydrophilic layer on the outer surface of calcite by Pullulan, in contrast to the absence of such layer on fluorite’s surface, results in an increased disparity in surface floatability between these two minerals, thereby enhancing the efficiency of flotation separation.

The paper systematically investigated the flotation behavior and interaction mechanisms of andalusite and quartz under sodium dodecyl sulfonate (SDS) through integrated experimental and computational approaches, including zeta potential measurements, Fourier-transform infrared (FTIR) spectroscopy, Materials Studio (MS)-based quantum chemical calculations, and single-mineral flotation tests. The results of zeta potential and infrared spectroscopy analysis indicated that SDS underwent strong chemical adsorption on the surface of andalusite, while the adsorption effect on the surface of quartz was not obvious. MS calculations showed that the {100} surface energy of andalusite was the lowest, and it was the most important dissociation surface. After SDS was adsorbed on the {100} surface of andalusite, the aluminum atoms on the surface of andalusite lost electrons, resulting in a significant increase in the number of positive charges they carried. The activity of oxygen atoms was enhanced, while the number of charges carried by silicon atoms changed relatively little. It was indicated that SDS adsorbed the active sites of Al atoms on the surface of andalusite. The results of the pure mineral flotation test further verified the accuracy of the previous test results, indicating that andalusite and quartz had a good flotation separation effect under the SDS system.