π-π Stacking-driven Self-Assembly Enables Low-Odor, Highly Selective Xanthate Collectors for Galena Flotation

Xanthates are the most widely employed collectors in industrial sulfide mineral flotation; however, they often cause severe malodor pollution and exhibit limited selectivity when separating sulfide minerals with similar surface properties. In this study, we applied a molecular self-assembly strategy by incorporating a nitrogen-containing linker and a dibenzyl motif into an ethyl xanthate framework to synthesize a novel xanthate collector, O-(2-(bis(phenylmethyl)amino)ethyl) xanthate (PAEX). DFT calculations indicate that the negative electrostatic potential of PAEX remains localized on the sulfur-containing xanthate moiety (which preserves the reactive center). Meanwhile, the benzyl groups provide a polarizable surface that improves π-π stacking-dominated intermolecular interactions, thereby intrinsically suppressing volatilization into the gas phase. Electronic nose measurements further confirm the low-odor advantage of PAEX, indicating that the characteristic sulfide response decreases by more than 74.78% compared with conventional isobutyl xanthate. Flotation experiments with galena and sphalerite demonstrate that PAEX achieves highly selective galena collection across a wide pH range. Interfacial characterizations demonstrate that PAEX coordinates with Pb(II) sites on the galena surface through the sulfur atoms of the xanthate group, forming PAEX(S)-Pb surface complexes. Moreover, PAEX adopts an ordered, upright adsorption configuration that forms a stable and compact hydrophobic film, significantly enhancing the wettability contrast between galena and sphalerite. Overall, the π-π stacking-assisted self-assembly strategy effectively overcomes odor and selectivity limitations of conventional xanthate collectors, providing strong industrial potential for green mineral processing and the efficient separation of complex sulfide ores.