XPS Characterization of Chalcopyrite, Tetrahedrite, and Tennantite Surface Products after Different Conditioning. 2. Amyl Xanthate Solution at pH 10

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Characterization of the surface products formed by the interaction of amyl xanthate solution at pH 10 with mineral samples of chalcopyrite (CuFeS2), tetrahedrite (Cu12Sb4S13), and tennantite (Cu12As4S13) was carried out by X-ray photoelectron spectroscopy (XPS). The experimental data collected directly after solution treatment and after successive sputterings have led us to determine the in-depth distribution of the different types of surface products formed by the diffusion of atoms from the bulk to the interface region and their interaction with aerated aqueous xanthate solution. The xanthate adsorption takes place by an electrochemical mechanism which involves the formation of cuprous xanthate (hydrophobic species) and metal hydroxides (hydrophilic species). In general, the following in-depth surface composition was found for the investigated mineral samples in contact with the xanthate solution: (i) the outermost layer contains the cuprous xanthate complex, which causes hydrophobic properties, and a small amount of metal hydroxide species (depending on the mineral sample), and (ii) below this hydrophobic layer are gradual changes leading to a structure with a composition very similar to the one expected for the bulk mineral sample. All the mineral samples show a copper enrichment in the interface region formed as a result of diffusion of copper atoms to the interface provoked by the adsorbed xanthate molecules. Sulfur-enriched structures, which were observed after treatment in solution without xanthate, are not observed in the presence of xanthate solution. The adsorbed amount of xanthate as well as the structure of the outermost layer, which is responsible for the mineral sample's hydrophobicity, varied dramatically. Tetrahedrite shows the fastest kinetics of xanthate adsorption with the formation of multilayer coverage of surface cuprous xanthate. On chalcopyrite and tennantite the adsorbed amount of xanthate is much lower, close to a monolayer coverage. The differences in the surface composition of these three minerals are governed mainly by a different mobility of copper atoms in their crystalline structures in the presence of xanthate in solution. Other metal atoms present in the mineral samples, i.e. antimony, arsenic, iron, zinc, and silver, do not take a significant part in the formation of the outermost adsorption layer.