The Relationship between Mineral Structure and Floatability Discussed from the Principle of Coordination Field

This study investigated the relationship between mineral crystal structure and floatability from the perspective of ligand field theory, explaining the influence of crystal structure on mineral floatability. The iron ions in hematite and pyrite possess d⁵ and d⁶ electronic configurations respectively, with 0 and 3 pairs of π electrons correspondingly. This difference prevents xanthate collectors from forming feedback π−bonds with hematite while enabling strong feedback π−bond formation with pyrite, resulting in strong collecting power of xanthate for pyrite but none for hematite. The Jahn−Teller effect explains the differential collecting behavior of xanthate towards copper oxide and copper sulfide minerals. In oxidized copper minerals, electrons occupying the dz² orbital repel xanthate molecules, thereby hindering the interaction between Cu²⁺ ions and xanthate-type collectors. For sphalerite containing d¹⁰ zinc ions, ions such as copper, gold, and silver exhibit high polarizability, which enhances the covalent interaction between these ions and collector molecules, thereby activating sphalerite. In pyrrhotite crystals with single S coordination, Fe²⁺ possesses only one pair of π electrons, leading to weak π back−bonding interaction with xanthate. The absence of vacant d−orbitals further hinders the formation of strong inner−sphere coordination complexes, making pyrrhotite less floatable than pyrite. For iron−bearing sphalerite containing tetrahedrally coordinated Fe²⁺ ions, the single π−electron pair results in weak π back−bonding with xanthate, creating distinct floatability characteristics compared to pyrite. In chalcopyrite, copper possesses more 3d π electron pairs than iron, leading to stronger covalent coordination with xanthate-type collectors, establishing copper as the reactive site. Additionally, spin−coupling effects of iron ions enhance the activity of copper ions.