A Novel Bipolar Surfactant, BETX, for Selective Flotation of Chalcopyrite: Folding-Synergistic Mechanism Based on Intramolecular Weak Interactions

Surfactants with multiple polar groups have shown promising applications, while the molecular mechanism that distinguishes them from conventional surfactants remains unclear. Herein, a novel surfactant, BETX, which contains two polar groups was designed, and the effect of intramolecular interaction on its molecular mechanism was elucidated. MD simulations, DFT calculations, and UV spectroscopy revealed that the BETX molecules fold due to π–π stacking and various other weak interactions, which enhances the binding ability of BETX to Cu2+ while reducing that to Fe3+. Interestingly, the synergism of ionic xanthate groups and nonionic thionocarbamate groups enables the thionocarbamate groups to react with Cu2+ in aqueous solutions. This selective synergistic behavior endowed BETX with excellent selective flotation ability for chalcopyrite, with a dosage an order of magnitude lower than that of traditional collectors. ToF-SIMS, FTIR, and XPS demonstrated that BETX interacts with chalcopyrite through the xanthate group and the deprotonated thionocarbamate group. Each N and S atom in the molecule can form chemical bonds with copper sites. Comparative assessments of Cu2+ binding between unfolded bipolar surfactants with rigid structures have confirmed the reinforcing effect of folding synergism in BETX molecules. The revelation of this intramolecular folding-synergistic mechanism holds profound significance, offering crucial insights into the operational mechanisms of multipolar surfactants and facilitating precise molecular design for future advancements.