Sulfur-containing species origin

Carbon-, nitrogen-, and sulfur-containing species account for most of the mass of aerosol particles. In spite of years of effort by many investigators, the exact chemical forms of carbon, sulfur, and nitrogen in these particles are not known nor are the formation mechanisms of these species known with certainty. There are many reasons for this situation, including the complexity of the system and the dependence of the apparent chemical composition on the analytical methods used. For example, wet chemical analyses of sulfur and nitrogen species report only ions in solution. These ions, however, may be originally water soluble (e.g., sulfate and ammonium from ammonium sulfate), or they may be ionic products of hydrolyzable species such as amides (1). Of course, insoluble species will not be detected by wet chemical techniques. 

The analysis in Reference 54 shows sulfur-bonding groups have nearly the same fluoro/hydroxy difference. While perhaps irrelevant for the current study, it is nonetheless interesting that it is for these sulfur-containing species that the original mimicry was devised in Reference 53a. 

Fig. 10. Catalytic cycle proposed for the final step of methanogenesis, involving a NinlF430 intermediate, modified for this review from a mechanism originally proposed by Jaun [83]. The F430 macrocyclic ligand is represented by a disk. Axial coordination to Ni by sulfur-containing species is likely, but not explicitly shown. The overall charge on the F430 species is not known nor indicated. Reproduced with modifications, with permission, from Reference [83], 1990, by Verlag Helvetica Chimica Acta, Basel, Switzerland...

The catalyst of Cheekatamarla and Lane lost 75% of its original surface area when etposed for more than 50 h to the sulfur containing feed, whereas only a 50% reduction in surface area was observed for the low sulfur feed [268]. In parallel, the dispersion of the platinum decreased from 51 to 35%. These workers explained these observations by two types of sulfur species being present on the catalyst surface firstly, physically adsorbed sulfur species and, secondly, their oxidised products, which were then irreversibly bound to the catalyst sites by chemical adsorption. The activity of the catalyst could be completely re-gained when it was reduced in 20 vol.% hydrogen (with a balance of helium) for 30 min at 800 °C. 

Eudistones A and B were obtained from an undetermined species of Eudistoma from the Seychelles Islands. Tintamine, shermilamine E and cydoshermil-amine D are three sulfur-containing pyridoacridines. These new alkaloids were extracted from Cystodytes viola-tinctus, whose specific name refers to the animal s color and whose origin is the lagoon of Mayotte. Tintamine is the first example of a pyridoacridine associated with a tropolone and shermilamine E is a rare example of an N-oxide derivative isolated from a marine organism. 

Sulfur is a rather exceptional element for several aspects. It can assume various oxidation states [1] and in these oxidation states it exists in a great number of different chemical forms. Sulfur is a constituent of a large number of industrial products (H2SO4, rubber vulcanization, for instance) and is also at the origin of a major pollutant (SO2) [2]. Sulfur can exist in more than ten allotropic forms at room temperature, that is, in a variety not found with any other element [3-5]. Orthorhombic sulfur is the most stable form at room temperature. It contains crown-shaped Sg molecules, which are stacked in a complex array. It can also be mentioned that the liquid and gaseous phases of sulfur are very complex [6, 7]. Undoubtedly, the existence of catenated species is a general feature of sulfur chemistry and is the basic reason for its complexity. 

Barix process Barium is fust added to the resin in the form of a liquid hydroxide. Subsequently, the resin is heated in the absence of oxygen and broken into its original components. Barium plays the role of catalyst in this depolymerization process and reacts with the sulfur in the cationic functional groups to form barium sulfate, which in turn acts as a binder for the metallic species in the waste. Moreover, the barium hydroxide adjusts the pH so that the metals contained in the resins stay in the residue after the steps of drying and destruction (IAEA, 2002). 

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