Dandan Wu

Through flotation test and combined with analyses of surface morphology, roughness, chemical composition, wettability, electrochemical characteristics and quantum chemical calculations, the NaIO4 selective depression mechanism was further revealed. Flotation test results show that under the solution pH of 9.0, with the concentrations of NaIO4 and PBX being 3×10-3 mol/L and 3×10-4 mol/L respectively, efficient separation of chalcocite and molybdenite can be achieved by using NaIO4. After the addition of NaIO4, the difference in flotation recovery between chalcocite and molybdenite increased to 87.56%. NaIO4 exerts a strong oxidative corrosion effect on chalcocite. Its surface roughness Ra increases from 9.35 nm to 20.20 nm, accompanied by a remarkable rise in the relative content of surface oxygen and copper hydroxide, as well as an obvious enhancement in the characteristic intensity of SO42-. The contact angle drops from 96.54° to 52.48°, leading to a substantial reduction in surface hydrophobicity. In contrast, molybdenite presents no obvious changes in roughness, elemental composition after treatment with sodium periodate, indicating its well-maintained stable surface properties. DFT calculation results reveal that NaIO4 can form stable Cu-O bonds on the chalcocite (0 0 1) surface via electronic interactions between Cu 3d and O 2p orbitals, thereby achieving efficient adsorption. Meanwhile, NaIO4 competes with PBX and forms I-S bonds.

The effect of the Fenton reagent, an environmentally compatible oxidant, on the separation of chalcocite and molybdenite was systematically investigated in this study. Microflotation tests revealed that the Fenton reagent exerts a significantly stronger depressive effect on chalcocite than on molybdenite, enabling efficient separation of the two minerals. At fixed sodium butyl xanthate (SBX) concentration and kerosene concentration of 5 × 10^-5 mol/L and Fenton reagent concentration ([FeSO₄]/[H₂O₂] = 1:1) of 1 × 10^-4 mol/L, under pH = 6, the separation was further enhanced, with chalcocite recovery dropping to 0.05% and molybdenite recovery reaching 95.03%. In the artificial mixed mineral system, both SBX concentration and kerosene concentration of ([SBX]/[kerosene] = 1:1) 5 × 10^-5 mol/L and Fenton reagent concentration ([FeSO₄]/[H₂O₂] = 1:1) of 1 × 10^-4 mol/L, under pH = 6, Cu recovery declined substantially from 89.42 to 12.76%, while Mo recovery remained at 87.24%, yielding a recovery differential of 74.48%. Surface characterization through LEIS, AFM, SEM-EDS, and contact angle measurements revealed that Fenton reagent treatment selectively increased the hydrophilicity of chalcocite. Chalcocite exhibited significantly higher increases in impedance, roughness, and surface oxygen content compared to molybdenite, indicating more extensive surface oxidation. ToF-SIMS analyses and XPS further confirmed strong oxidation on chalcocite surfaces, in contrast with only mild oxidation on molybdenite. This differential oxidation facilitated the formation of Cu(OH)₂, which acts as the primary depressant on chalcocite, thereby effectively depressing its floatability. The DFT results indicate that the adsorption energy of ^•OH molecules on the Cu sites on the surface of chalcocite is -144.79 kJ/mol and the bond length of Cu-O is 2.187 Å, with a population of 0.28. The adsorption energy of ^•OH molecules on the S sites on the surface of molybdenite is -7.85 kJ/mol, the bond length of S-O is 3.541 Å, and the population is close to zero. This suggests that ^•OH molecules are more likely to interact with the copper sites on the surface of chalcocite (001). Overall, as a stable, effective, and environmentally compatible oxidant, the Fenton reagent demonstrated strong potential for the industrial separation of copper-molybdenum sulfides.