Transport sulfur extraction

This scheme for electron transport through the cytochrome bc1 complex is known as the Q cycle. The role of the iron-sulfur protein was confirmed by extracting this protein from the cytochrome bc1 complex. If the iron-sulfur protein is removed, electron transfer from UQH2 to cytochrome c is prevented. This shows that the iron-sulfur protein operates upstream of cytochrome cj, even though its E° is more positive than that of the cytochrome (see fig. 14.7 and table 14.1). 

The definition of environmental chemistry given above is illustrated for a typical environmental pollutant in Figure 2.3. Pollutant sulfur dioxide is generated in the anthrosphere by combustion of sulfur in coal, which has been extracted from the geosphere. The S02 is transported to the atmosphere with flue gas and oxidized by chemical and photochemical processes in the atmosphere to sulfuric acid. The sulfuric acid, in turn, falls as acidic precipitation, where it may have detrimental effects, such as toxic effects, on trees and other plants in the biosphere. Eventually the sulfuric acid is carried by stream runoff in the hydrosphere to a lake or ocean, where its ultimate fate is to be stored in solution in the water or precipitated as solid sulfates and returned to the geosphere. 

Sulfur dioxide can be prepared by several methods, the most common of which is the combustion of sulfur or pyrites (FeS2). A variety of furnaces have been developed for carrying out this reaction. Each type of furnace produces sulfur dioxide of different purities. After production, the sulfur dioxide is normally cooled and compressed to convert it to liquid form. Liquid sulfur dioxide is more easily stored and transported than the gaseous form. Sulfur dioxide is also obtained as the byproduct of a number of industrial operations, especially the smelting of metallic ores. Smelting is the process by which a metal is extracted from its ore by heating in air. Since many ores are sulfides, this process often results in the formation of sulfur dioxide, which can be captured as a byproduct of the operation. Finally, sulfur dioxide can be produced by the direct combustion of sulfur itself ... 

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