XPS CHARACTERIZATION OF CHALCOPYRITE, TETRAHEDRITE, AND TENNANTITE SURFACE PRODUCTS AFTER DIFFERENT CONDITIONING .1. AQUEOUS-SOLUTION AT PH

Characterization of the surface products formed by the interaction of aqueous solution at pH 10 with mineral samples of chalcopyrite (CuFeS2 ), tetrahedrite (Cu12Sb4S13), and tennantite (CU(12)AS(4)S(13)) was ca rried out by X-ray photoelectron spectroscopy(XPS). The experimental d ata collected directly after treatment with aqueous solution and after successive sputtering have led us to determine the in-depth distribut ion of the different types of surface products formed by the diffusion of metal atoms from the bulk structure to the interface and their int eraction with aerated water. In general, the following in-depth surfac e composition was found for the investigated mineral samples: (i) the outermost thin layer consists of hydrophilic species, mainly ferric or cupric (depending on the mineral sample) oxides/hydroxides and adsorb ed water, (ii) the next layer is a sulfur-enriched structure with a gr adually changing composition with hydrophobic properties which vary si gnificantly among the minerals, and (iii) the innermost layer has a bu lk mineral composition and structure. In the case of chalcopyrite the separation between the outermost hydrophilic layer (iron oxides/hydrox ides) and the internal hydrophobic sulfur-rich layer is more pronounce d than for other mineral samples. This is the reason that the outermos t hydrophilic thin layer can be relatively easily removed mechanically and/or by dissolution during a strong agitation. This involves a stro ng increase in the hydrophobicity of chalcopyrite. In the case of tetr ahedrite and tennantite the outermost hydrophilic layer consists mainl y of copper oxides/hydroxides and it is not well separated from the re st of the surface structure. This implies that the two minerals remain hydrophilic. Tetrahedrite forms the copper oxides/hydroxides product much more quickly with a major amount of cupric species, whereas tenna ntite oxidation, under the same conditions, yields a small amount of c uprous surface species, The differences in surface composition of thes e three minerals, caused by the different mobilities of copper atoms i n their crystalline structures, are vitally important for their separa tion in the presence of surfactants. It should be noted that although tetrahedrite and tennantite contain a significant amount of other elem ents, they are not concentrated in the outermost layer. On the contrar y their surface concentrations are several times lower than those foun d for the bulk composition.