Sulfur compounds oxides

Oxidative desulfurization of sulfur compounds Oxidation of thiophene and derivatives with hydrogen peroxide using Ti-Beta catalyst... 

The presence of sulfur compounds in the combustion process can affect the nitrogen oxides, as well. Thus, it is important to study sulfur compound oxidation not only to find alternative or new means of controlling the emission of objectionable sulfur oxides, but also to understand their effect on the formation and concentration of other pollutants, especially NO,. ... 

In this retrospective analysis of our current understanding of chemolithotrophic sulfur compound oxidation, I have sought to show how the hve research papers (and two reviews) on T. thioparus published by Peck and... 

Release to air prescribed substances Oxides of sulfur and other sulfur compounds Oxides of nitrogen and other nitrogen compounds Oxides of carbon... 

When the hrst photosynthetic sulfur-compound oxidizers hrst appeared, the development of full sulfureta would have been possible. Sulfate reducers would take sulfate from the external environment and eventually produce H2S. Then the photosynthetic oxidizers would reverse the steps, e.g.,... 

Sulfur Compound Oxidizing Bacteria in Industrial Applications. 181... 

Fig.1 The biological sulfur cycle. SB sulfur compound oxidizing bacteria SRB sulfate reducing bacteria...

In natural ecosystems the sulfur cycle should be in balance, meaning that the amount of sulfide that is oxidized should correspond to the amount of sulfate that is reduced. Such a balance can be found in a sulfuretum . This is a syntrophical community of bacteria in which H2S produced by sulfate reducing bacteria is reoxidized by the sulfur compound oxidizing bacteria. 

Table 1 Properties of some sulfur compound oxidizing bacteria ...

Apart from the above sulfide oxidation reactions, other sulfur compounds, such as sulfur and thiosulfate, can be oxidized by sulfur compound oxidizers. Furthermore, nitrate can be used as oxidant instead of oxygen. In Table 2 a list is shown of some other sulfur compound oxidation reactions occurring in chemotrophic sulfur compound oxidizing bacteria. It should be... 

Elemental sulfur is often observed as an intermediate product in the oxidation of sulfide to sulfate in sulfur compound oxidizing bacteria. It can be present in considerable concentrations but will eventually be further oxidized to sulfate. The elemental sulfur is stored in sulfur globules, which some bacteria deposit inside the cell membrane and others outside the cell membrane. Later in this chapter the properties of these sulfur globules are discussed. 

The optimum pH of growth of the bacteria differs per species. Neutral and acidiphilic sulfur compound oxidizing bacteria have been long known, mostly isolated from marine or freshwater sediments (e.g., [2, 5]). From highly alkaline salt lakes a number of alkaliphilic sulfur compound oxidizing bacteria have been isolated, both phototrophic [8] and chemotrophic [10, 16]. The technological relevance of alkaliphilic sulfur compound oxidizers is discussed later in this chapter. 

Sulfur globules produced by bacteria excreting the globules outside the cell membrane have also been studied. Especially for biotechnological applications these sulfur compound oxidizing bacteria are interesting since they allow an easy separation of the sulfur from the bacteria. In Fig. 5 sulfur globules can be seen which have been excreted by a Thiobacillus bacterium. 

In chemical oxidation reactions, the first oxidation step (forming of sulfide radicals) is catalyzed by metal-ions like Fe, and Cu. In most sulfur compound oxidizing bacteria, the first step in the oxidation of sulfide to sulfur is catalyzed by the enzyme flavocytochrome c [3]. In a number of bacteria with the capacity to oxidize sulfide to sulfur, flavocytochrome c has not been found and other cytochromes or quinones are believed to catalyze the oxidation of sulfide in these organisms. 

A limitation to the alkalinity of the liquid recycle is the optimum pH of growth of the bacteria in the bioreactor. Use of alkaliphilic sulfur compound oxidizing bacteria is therefore very interesting from a technological point of view. 

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