It is difficult to separate molybdenite and chalcopyrite by froth flotation due to the good floatability of the two minerals. In this paper, the separation of copper-molybdenum sulfide minerals was realized by using pullulan polysaccharide (PU) as the depressant. The flotation test results showed that the copper concentrate grade increased from 16.24 to 29.86%, and the copper concentrate recovery reached 83.55% under low alkali conditions. The selective separation mechanism of the two minerals by PU was revealed through contact angle measurements, ζ-potential measurements, Fourier transform infrared (FTIR) spectroscopy analyses, and X-ray photoelectron spectroscopy (XPS) analyses. The ζ-potential and contact angle results showed that PU is more easily adsorbed on molybdenite to strengthen the hydrophilicity of molybdenite. The FTIR and XPS results showed that PU is adsorbed on molybdenite by physical interactions, and hydrophobic interactions and hydrogen bonding play a major role.

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.

Bulk flotation is usually used in the flotation of Cu-Fe sulfide ore, and the subsequent concentrate is difficult to be separated because the minerals have adsorbed the collector. In this paper, flotation tests showed that calcium hypochlorite (Ca(ClO)2) had a stronger depression effect on pyrite...