Unraveling H2O2-stimulated surface oxidation of non-magnetic pyrrhotite and pentlandite by underlying electronic structures

Abstract

The selective flotation of pentlandite from non-magnetic pyrrhotite is a long-standing issue. To contribute to solving this issue, we report our fundamental understanding of the selective depression of non-magnetic pyrrhotite in pentlandite flotation using H2O2. Reactions of H2O2 were studied using chronopotentiometry (CP) tests and dissolved oxygen (DO) tests. Surface oxidations were studied with surface composition depth profiles of X-ray photoelectron spectrometry (XPS) and time-of-flight secondary ion mass spectrometry (ToF-SIMS). It was found that H2O2 reduction stimulated the surface oxidation of non-magnetic pyrrhotite, meanwhile, H2O2 reduction on pentlandite was balanced by the oxidation of H2O2. The different responses to H2O2 conditioning were attributed to the distinct electronic structures of pyrrhotite and pentlandite, which were calculated based on density functional theory (DFT). For pyrrhotite, the higher S 3p band center than its Fe 3d band center suggests a strong interaction between surface sulfur anions and H2O2 redox reaction intermediates such as OH* and OOH*, resulting in easy sulfur oxidation. For pentlandite, the lower S 3p band center than its metal d band centers suggests a weak interaction between the sulfur anions and the H2O2 redox reaction intermediates, protecting sulfur from oxidation and rendering high catalysis effects to active metallic centers.