PDF Publication Title:
Text from PDF Page: 174
164 Ralf Steudel duced compounds like thiosulfate and tetrathionate, probably via the follow- ing reactions: 2S2O2 ! S4O2þ2e ð21Þ 36 H2OþS4O2 !HSSSOþHSO ð22Þ 634 In cultures of sulfur bacteria the reactions at Eqs. (20)–(22) are catalyzed by appropriate enzymes. The sulfane monosulfonate formed in the reaction at Eq. (22) is unstable and decomposes to polythionate anions and elemental sulfur which are the components of Raffo and Selmi sols as shown above; see Eqs. (10) and (11). These reactions take place, for example, if cultures of Acidithiobacillus ferrooxidans (formerly Thiobacillus ferrooxidans) are “in- cubated” (mixed) with tetra- or pentathionate at 30 C in air. After some time all polythionate anions with up to 17 sulfur atoms could be detected by ion-pair chromatography in the filtrated aqueous phase while the sulfur globules excreted extracellularly were isolated and extracted by CS2. Accord- ing to a HPLC analysis this extract contained S8 and small amounts of the homocycles S6, S7, and S12 [53]. Other types of sulfur bacteria produce globules which seem to consist of organic polysulfanes R-Sn-R although the chain-terminating groups have not been identified yet [54, 55]. Many times it has been observed that sulfur bacteria enter chemical plants in which sulfur compounds are treated. Sulfate reducing bacteria (SRB) produce sulfide ions which may then be used by oxidizing bacteria like thiobacilli to generate sulfur sols consisting of polythionates. In this way, serious disturbances of the production conditions may occur. This holds in particular for desulfurization plants of the Stretford and Sulfolin type in which hydrogen sulfide is oxidized to elemental sulfur which is sup- posed to crystallize rapidly to be separated by flotation [5]. Mixed cultures of sulfur bacteria are used industrially for the desulfuriza- tion of wastewater and waste gases by biological conversion to elemental sul- fur which has colloidal properties [56, 57]. References 1. P. P. von Weimarn, B. W. Malyschew, Kolloid-Z 1911, 8, 216; P. P. von Weimarn, Kolloid- chem. Beihefte 1926, 22, 38. 2. M. Raffo, Kolloid-Z. 1908, 2, 358. 3. F. Selmi, J. Prakt. Chem. 1852, 57, 49 and references cited therein. 4. H. Freundlich, P. Scholz, Kolloidchem. Beihefte 1922, 16, 234. 5. R. Steudel, Ind. Eng. Chem. Res. 1996, 35, 1417. 6. H. Debus, J. Chem. Soc. 1888, 53, 278. The “new allotrope d-sulfur” proposed in this publication is in reality a mixture of long-chain polythionic acids (see the Section 3.3: Selmi Sols). 7. B. Meyer, Sulfur, Energy, and Environment, Elsevier, Amsterdam,1977, p. 63. 8. V. K. LaMer, R. H. Dinegar, J. Am. Chem. Soc. 1950, 72, 4847. 9. J. Boulege, Phosphorus Sulfur 1978, 5, 127; see also ref. [8].PDF Image | Topics in Current Chemistry
PDF Search Title:
Topics in Current ChemistryOriginal File Name Searched:
Elemental-Sulfur-und-Sulfur-Rich-Compounds-I.pdfDIY PDF Search: Google It | Yahoo | Bing
Sulfur Deposition on Carbon Nanofibers using Supercritical CO2 Sulfur Deposition on Carbon Nanofibers using Supercritical CO2. Gamma sulfur also known as mother of pearl sulfur and nacreous sulfur... More Info
CO2 Organic Rankine Cycle Experimenter Platform The supercritical CO2 phase change system is both a heat pump and organic rankine cycle which can be used for those purposes and as a supercritical extractor for advanced subcritical and supercritical extraction technology. Uses include producing nanoparticles, precious metal CO2 extraction, lithium battery recycling, and other applications... More Info
CONTACT TEL: 608-238-6001 Email: greg@infinityturbine.com (Standard Web Page)