Fracture‐induced reconstruction of a chalcopyrite (CuFeS₂) surface

Abstract

Two factors contributing to the high binding energy asymmetry of the S 2p XPS peak for virginal chalcopyrite (CuFeS 2 / surfaces have been identified. The Cu, Fe and S 2p spectra of freshly fractured surfaces of chalcopyrite have been found to display a loss feature at ∼2.6 eV that is attributed to an interband transition S 3p → Fe 3d, from occupied S levels to unoccupied Fe levels. For leached chalcopyrite systems, intensity on that side of the S 2p peak sometimes has been interpreted erroneously in terms of oxidized species such as polysulphides. A second prominent S 2p component has been determined at a binding energy of 161.9 eV and identified as the sulphide dimer S 2 2− . With supporting evidence, a simultaneous surface reconstruction and redox reaction model has been developed for the fracturing of chalcopyrite, leading to an exposed surface phase of about two layers thick with a 50% pyritic content. The pyritic nature of the fractured chalcopyrite surface has implications for understanding the leaching chemistry of chalcopyrite.

The Influence of Impurity Monovalent Cations Adsorption on Reconstructed Chalcopyrite (001)-S Surface in Leaching Process

“…Furthermore, the electron densities of the unrelaxed and relaxed chalcopyrite (001)-S surfaces shown in Figure 3 assist in verifying that a bond was clearly formed between two sulfur atoms at the first atomic layer after relaxation, as the electron density of the uppermost S atoms at the relaxed (001)-S surface (Figure 3b) overlapped, definitely different from the unrelaxed (001)-S surface shown in Figure 3a. All these pieces of evidence, in addition to that observed in the experiment using synchrotron-or lab-based XPS techniques [20,27,28], support the formation of disulfides on the reconstructed (001)-S surface. the bottommost atomic layer (along the c axis) of the relaxed unit is significantly reduced due to reconstruction.…”

Ionic liquids for metal extraction from chalcopyrite: solid, liquid and gas phase studies

“…Apart from the common chalcopyrite peaks reported in the literature (1-3), one additional peak (4) was found at 162.9 ± 0.2 eV and this peak is commonly attributed to S 0 that originates either from elemental sulfur or is hypothesised to be the central atoms of long chain polysulfides, both eventualities are commonly reported to result from leaching. 27,33,35 The surface compositions of the leached samples have changed after the leaching, as expected. An additional peak was found in the spectrum of samples leached in [HC 4 im][HSO 4 ] solution at 163.8 ± 0.1 eV, which is normally reported for polysulfide species.…”

“…[33][34][35] The deconvoluted spectra in the S 2p region are shown in Fig. S8 and S9 and resultant comparison of cleaved and leached surfaces are summarised in Table 6.…”

Surface morphology ofCuFeS2: The stability of the polar(112)/(112¯)surface pa

“…De Oliveira and Duarte performed DFT-GGA calculations to investigate the geometry and electronic structure of the relaxed sulfur-and metal-terminated nonpolar (001) surfaces [22]. Their analysis predicted oxidation of S 2− to S − coupled with reduction of Fe 3+ to Fe 2+ at the surface, leading to the formation of surface disulfide S 2− 2 and iron disulfide Fe 2 S 2 phases, which have also been observed experimentally using x-ray photoelectron spectroscopy (XPS) [23,24]. De Oliveira et al reached similar conclusions using DFT-GGA calculations on an expanded set of nonpolar surfaces [25].…”