Influence of iron impurity on floatability of iron-bearing sphalerite

Iron impurity is the most common impurity element in sphalerite, and its content has a significant influence on the flotation behavior of sphalerite. To systematically investigate the mechanism by which iron content affects the flotation behavior of sphalerite, this study employed density functional theory (DFT) simulations combined with coordination chemistry principles to analyze the effects of iron content and its spin configuration on the electronic structure and floatability of sphalerite. The results indicate that as the iron content increases, the band gap of sphalerite gradually narrows. Under low iron content conditions, the reduced band gap favors the transfer of electrons, where iron impurities exist as high-spin Fe²⁺. The 3d orbitals of Fe²⁺ can provide a pair of π electrons, enabling the formation of a weak feedback π-bond with xanthate, thereby enhancing the floatability of sphalerite. In contrast, under medium and high iron content conditions, further narrowing of the band gap intensifies electrochemical interactions, promoting the oxidation of Fe²⁺ to Fe³⁺. Since Fe³⁺ lacks π electron pairs in its 3d orbitals, it cannot form a feedback π-bond with xanthate, leading to a significant decrease in the floatability of sphalerite. The theoretical calculations in this study are consistent with experimental flotation results, providing deeper insights from the perspective of coordination chemistry into how iron content influences the flotation behavior of sphalerite, and offering important theoretical support for the flotation of iron-bearing sphalerite.