Synchrotron XPS, NEXAFS, and ToF-SIMS studies of solution exposed chalcopyrite and heterogeneous chalcopyrite with pyrite

The surface species present on two pure chalcopyrite samples (one with a smooth fracture surface; one with a rough fracture surface) and one heterogeneous sample containing both chalcopyrite and pyrite have been studied using synchrotron X-ray photoelectron spectroscopy (SXPS), near-edge X-ray Absorption Fluorescence Spectroscopy (NEXAFS), and time-of-flight secondary ion mass spectrometry (ToF-SIMS). The measurements were performed for samples fractured in N₂ and for samples subsequently exposed to pH 1 HCl solution for 2 h. The comparison of freshly fractured and solution exposed mineral surfaces has allowed for the investigation of the role of other mineral phases on the development of chalcopyrite surface species, and the role of chalcopyrite grain size on surface species development. Analysis of the chalcopyrite region of each sample indicates that increased surface roughness and the presence of pyrite in intimate contact with chalcopyrite increases the formation of surface sulfur species that are implicated in the formation of passivating layers on leached chalcopyrite surfaces. ToF-SIMS analysis of the chalcopyrite and pyrite regions of the heterogeneous sample support the conclusions obtained from the synchrotron surface analysis experiments.