Effect of Carbon Chain Structure on the Quantum Chemical Properties of Xanthate Collector Molecules

Xanthates are commonly used as flotation collectors for sulfide ores, and the length and structure of the carbon chain will affect their capture performance. Based on density functional theory (DFT), the bond structure characteristics and frontier orbital energies of polar functional groups −OCSS⁻ of normal and isomeric xanthate ions with C₁ to C₅ carbon chain lengths were calculated, the orbital coefficient, Mulliken charge, electrophilicity and nucleophilicity of the S atoms were also calculated. The results show that the length of the carbon chain has no significant effect on the structural characteristics of the functional group bonds of the collector, the H atoms on the carbon chain have weak hydrogen bonding with the polar group S atoms, which increase with the growth of the carbon chain, resulting in subtle differences in the functional group bond structure. The two S atoms in the polar functional groups of xanthate ions have similar charges and are both nucleophilic, but the nucleophilicity of the S atoms varies, resulting in different adsorption abilities on mineral surfaces. Except for butyl and isobutyl xanthate ions, the energy difference between the highest occupied molecular orbital (HOMO) of isomeric xanthate ions and the lowest unoccupied orbital (LUMO) of pyrite is lower than that of the normal xanthate ions. This indicates that isomers are beneficial for enhancing the collection ability of collectors, which is consistent with the calculated binding energy of xanthate ions and Fe²⁺. Among them, isopropyl and isobutyl xanthate ions have higher binding energies with Fe²⁺.