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Abstract: Synchrotron XPS and Cu [L.sub.2,3]-edge NEXAFS spectroscopic data for a natural tetrahedrite surface prepared by fracture under UHV were in accord with the composition of the mineral and its [...]

The feasibility of investigating the adsorption of n-octanohydroxamate collector on copper and iron oxide minerals with static secondary ion mass spectrometry has been assessed. Secondary ion mass spectra were determined for abraded surfaces of air-exposed copper metal, malachite, pseudomalachite and magnetite that had been conditioned in aqueous potassium hydrogen n-octanohydroxamate solution, as well as for the corresponding bulk CuII and FeIII complexes. In each case, the chemical species present at the solid/vacuum interface of a similarly prepared surface were established by X-ray photoelectron spectroscopy. The most abundant positive and negative metal-containing fragment ions identified for the bulk complexes were also found to be diagnostic secondary ions for the collector adsorbed on the oxide surfaces. The relative abundances of those diagnostic ions varied with, and could be rationalised by, the monolayer or multilayer coverage of the adsorbed collector. However, the precise mass values for the diagnostic ions were not able to corroborate the different bonding in the copper and iron hydroxamate systems that had been deduced from photoelectron and vibrational spectra. Parent secondary ions were able to provide supporting information on the co-adsorption of hydroxamic acid at each conditioned surface. [ABSTRACT FROM AUTHOR]

X-ray photoelectron and absorption spectra have been obtained for natural specimens of cubanite and compared with the corresponding spectra for chalcopyrite. Synchrotron X-ray photoelectron spectra of surfaces prepared by fracture under ultra-high vacuum revealed some clear differences for the two minerals, most notably those reflecting their different structures. In particular, the concentration of the low binding energy S species formed at cubanite fracture surfaces was approximately double that produced at chalcopyrite surfaces. However, the core electron binding energies for the two S environments in cubanite were not significantly different, and were similar to the corresponding values for the single environment in chalcopyrite. High binding energy features in the S 2 p and Cu 2 p spectra were not related to surface species produced either by the fracture or by oxidation, and most probably arose from energy loss due to inter-band excitation. Differences relating to the Fe electronic environments were detectable, but were smaller than expected from some of the observed physical properties and Mössbauer spectroscopic parameters for the two minerals. X-ray absorption and photoelectron spectra together with the calculated densities of states for cubanite confirmed an oxidation state of CuI in the mineral. It was concluded that the best formal oxidation state representation for cubanite is CuI(Fe2)VS. [ABSTRACT FROM AUTHOR]

X-ray photoelectron and absorption spectra have been obtained for natural specimens of cubanite and compared with the corresponding spectra for chalcopyrite. Synchrotron X-ray photoelectron spectra of surfaces prepared by fracture under ultra-high vacuum revealed some clear differences for the two minerals, most notably those reflecting their different structures. In particular, the concentration of the low binding energy S species formed at cubanite fracture surfaces was approximately double that produced at chalcopyrite surfaces. However, the core electron binding energies for the two S environments in cubanite were not significantly different, and were similar to the corresponding values for the single environment in chalcopyrite. High binding energy features in the S 2 p and Cu 2 p spectra were not related to surface species produced either by the fracture or by oxidation, and most probably arose from energy loss due to inter-band excitation. Differences relating to the Fe electronic environments were detectable, but were smaller than expected from some of the observed physical properties and Mössbauer spectroscopic parameters for the two minerals. X-ray absorption and photoelectron spectra together with the calculated densities of states for cubanite confirmed an oxidation state of CuI in the mineral. It was concluded that the best formal oxidation state representation for cubanite is CuI(Fe2)VS. [ABSTRACT FROM AUTHOR]