5-Methyl-2-mercaptobenzoxazole Adsorbed onto Chalcocite (Cu2S): An XPS and X-AES Study

XPS (X-ray Photoemission Spectroscopy) and X-AES (X-ray excited Auger Electron Spectroscopy) studies have been carried out on the reaction between natural chalcocite and solutions of 5-methyl-2-mercaptobenzoxazole, a new synthetic flotation collector and a derivative of mercaptobenzoxazole (C8H7NOS) (MMBO). The XPS Cu(2p), Cu(3s), S(2p), N(1s), O(1s), and C(1s) lines and Cu L3M4.5M4.5 X-ray excited Auger electron spectra were detected for the Cu-MMBO complex and for chalcocite surfaces before and after immersion in MMBO solutions at different concentrations (from 10-6 to 10-3M) and in water. The S(2p), N(1s), O(1s), and C(1s) lines were recorded for MMBO bulk sample. The analysis of Cu L3M4.5M4.5 Auger spectra and the binding energy shift of the S(2p) and N(1s) peaks from the MMBO during the adsorption suggest that a chemical bond is formed between collector and chalcocite. The chemical bond occurring between copper atoms and collector species does not vary with the solution concentration; in fact there is no alteration in either the shape or the binding energy of the S(2p) and N(1s) lines. On the basis of Cu L3M4.5M4.5 Auger spectra and the quantitative analysis of the S(2p) and Cu(3s) peaks, it seems possible to separate monolayer and multilayer adsorption from each other. No evidence of any Cu(II) species on the surface was found.