The use of the Auger parameter and of chemical state plots 16,17 was found to be useful for highlighting the chemical state of the elements on sulfide minerals but, in the previous works, sulfur speciation by means of XPS and XAES was carried out without any attempt of curve fitting of the X-ray induced Auger SKLL signal. 15 The identification of sulfur species at the surfaces of the minerals is thus essential to clarify and thus to control the oxidation mechanism. Sphalerite (ZnS) on the other hand, is also bio-oxidized but in this case the mechanism which takes place should have the polysulfides as intermediate.
15 Pyrite (FeS 2) for example, is known to be bio-leached according to a mechanism that leads to the formation of sulfate ions: thiosulfates are proposed to be present as intermediates. In fact, it is acknowledged, that different sulfide minerals follow different bio-oxidation paths. 9Īuthors have been involved over the last decade in research on arsenic bearing sulfide minerals oxidation 10–14 and bio-oxidation and particular attention was devoted to the investigation of the surface alteration of the minerals by means of surface analytical techniques (XPS and XAES) in order to clarify the mechanism of oxidative dissolution especially for enargite.
Sulfur speciation is of crucial importance for studies on portable storage devices (rechargeable Li–S batteries), 1–3 on mineral processing and oxidation processes, 4,5 on tribology, 6,7 on sorbents for desulfurization 8 and on corrosion phenomena. Introduction The problem of sulfur speciation at the surfaces of materials is of general interest, involving chemists, geochemists, physics and material scientists. Also for the surface of mineral sulfides, terminal S atoms and central S atoms in the polysulfide chains can successfully be identified. An application of this approach tested on commercial alkali polysulfides is provided for the curve fitting of SKLL signals and sulfur speciation of three different sulfide minerals enargite (Cu 3AsS 4), chalcopyrite (CuFeS 2) and arsenopyrite (FeAsS). This behavior can be rationalized with the fact that the negative charge in polysulfide chains is located mainly on sulfur atoms in the terminal position indeed, sulfur present as central S shows a binding energy shift of −0.6 eV with respect to elemental sulfur (S 8), and sulfur in terminal S a shift of −2.4 eV. K 2S n, sulfur atoms both in central or terminal positions are found on the same line with slope −1 indicating similar final state effects. On the other hand, for a given polysulfide, e.g. −3 irrespective of the cation indicating similar initial state effects. Sulfur atoms in the central or terminal position, respectively, are found on a line with slope ca. The different sulfur chemical states present on the surface (sulfide S 2−, central S and terminal S in polysulfide chains) could be unambiguously assigned in the chemical state plot. In high concentrations, hydrogen sulfide can cause death by means of respiratory paralysis, and sulfur dioxide is known to be one of the causes of acid rain and a dangerous component in air pollution.The identification of surface sulfide and polysulfide species based on the curve fitting of S2p photoelectron spectra and, for the first time, of X-ray excited S KLL Auger spectra has been performed. Sulfuric acid is commonly known as battery acid. An important manufactured chemical, sulfuric acid, is produced using sulfur. Even one of Jupiter’s moons owes it’s colors to various forms of sulfur.
Sulfur is found in meteorites, volcanoes, and hot springs. Obtained from: pure form or as sulfide/sulfate mineralsĪs a minor component of fats, body fluids, and skeletal materials, this pale yellow element is essential to human life. Name origin: Sanskrit sulvari, arabic sufra