Comparative DFT Study of Hydration Interactions of Representative Flotation Collector Head Groups

During flotation, the hydration behavior of collector head groups plays an important role in determining collector hydrophilicity and interfacial adsorption behavior. However, although computation-assisted flotation studies have extensively investigated collector–mineral interactions, systematic comparisons of the intrinsic hydration characteristics of different collector head groups under unified computational conditions remain limited. In this work, density functional theory (DFT) calculations using the B3LYP functional with Grimme dispersion correction were conducted to investigate the hydration interactions between water molecules and representative head groups of five sulfide mineral collectors, including xanthate (X), dithiocarbamate (DTC), dithiophosphate (DTP), dithiophosphinate (3418A), and thiocarbamate (Z-200), and five oxide mineral collectors, including oleate (OA), oxidized paraffin soap (OPS–C12), dodecyl sulfonate (DS), styrene phosphonic acid (SPA), and salicylhydroxamic acid (BHA). The results show that oxide mineral collectors exhibit significantly stronger hydration interactions than sulfide mineral collectors. Sulfide collectors mainly form weak S···H–O hydrogen bonds with relatively long H-bond distances (2.27–2.61 Å), whereas oxide collectors predominantly form stronger O···H–O hydrogen bonds with shorter distances (1.66–2.24 Å). The total hydration binding energies of sulfide collectors range from −150 to −290 kJ/mol, while those of oxide collectors range from −244 to −491 kJ/mol. Among the studied collectors, SPA exhibits the strongest hydration tendency due to its highly charged phosphonate group, whereas Z-200 shows the weakest hydration interaction. The results indicate that hydration behavior is strongly influenced by head group type, charge state, and hydrogen-bond characteristics.