An XPS Study of Sphalerite Activation by Copper

Abstract

X-ray photoelectron spectroscopy (XPS) was used to study the kinetics and mechanisms of sphalerite activation in a 10-4 M CuSO4 solution at pH 9.2. The activation was fast during the first 10 min, after which the rate decreased exponentially. The increase in the amount of copper ion uptake was accompanied by the displacement of zinc ions from the sphalerite surface, indicating that the mechanism of copper uptake is one of displacement rather than adsorption. The XPS data show that the kinetics of activation increased considerably in a deoxygenated CuSO4 solution. Both the conventional XPS and synchrotron radiation XPS (SR-XPS) analyses show that copper activation involves a mechanism in which Cu2+ ions are reduced to the Cu(I) state, while the sulfur in ZnS is oxidized. Activation in the absence of oxygen and at an open circuit results in the formation of a CuS-like product, while in an air-saturated solution copper polysulfides are formed. The latter mechanisms are supported by the appearance of two distinct S(2p) doublets representing S- and S0 species at higher binding energies. When copper-activated sphalerite was conditioned in an air-saturated solution of pH 9.2, the CuS-like activation product is oxidized in preference to unactivated ZnS. The oxidation resulted in a loss of copper from the sphalerite surface, which may be detrimental to flotation.

A highly efficient polysulfide mediator for lithium–sulfur batteries

“…4a) shows a 1:1 ratio of the two S2p 3/2 contributions at 161.7 and 163.1 eV, ascribed to the terminal (S T À 1 ) and bridging sulfur (S B 0 ) atoms, respectively. This assignment is in accord with the chain structure of Li 2 S 4 , where the sulfur atoms at both ends have a formal charge of ( À 1), while those in the middle bear a formal charge of (0) 32,39 . Figure 4e displays the XPS Mn 2p 3/2 spectra of d-MnO 2 , which is mainly composed of Mn 4 þ , with its nearsurface enriched in Mn 3 þ relative to the bulk 40 .…”

“…When the cell was discharged to 2.15 V, the presence of longchain polysulfides is evidenced by strong S2p 3/2 contributions at 161.7 (S T À 1 ) and 162.9 eV (S B À 2 ) (Fig. 5a) 32,39 , with their 1:2 ratio suggesting a chain length approximately equal to Li 2 S 6 owing to the 2:4 ratio of terminal/bridging sulfur in this LiPS. Elemental sulfur was also detected at this and other intermediate states of discharge, consistent with incomplete reaction and/or the disproportionation of metastable polysulfides such as Li 2 S 8 to form Li 2 S 6 and sulfur as previously reported 45 .…”

Surface-enhanced redox chemistry of polysulphides on a metallic and polar host for lithium-sulphur batteries

“…The assignment is based on comparison with values reported for copper polysulphides 32 and the similarity of the spectrum to that of other polysulphides we synthesized ( Supplementary Fig. 4a,b).…”

Subaqueous Disposal of Mill Tailings

“…The activation product was assumed to be CuS-like, as shown by Yoon and his co-workers (Kartio et al, 1996;Yoon and Chen, 1996;Chen andYoon, 1997, 1999a& b). Table 3 shows the effect of concentration of Fe3+ ions in deoxygenated pH 2 buffer solution in Cell 2, whereas Cell 1 contained copper-activated sphalente in 104 M ICEX solution at pH 6.8.…”