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Organic Sulfur Compounds (organic + sulfur_compound)
Kinds of Organic Sulfur Compounds Selected AbstractsUse of Topological Indices of Organic Sulfur Compounds in Quantitative Structure-Retention Relationship StudyMOLECULAR INFORMATICS, Issue 9 2005F. Safa Abstract Structure-gas chromatographic retention index models were developed for some organic sulfur compounds at four different temperatures (60, 80, 100 and 120,°C) using only topological descriptors. At first, regression models were generated for each temperature separately with high values of multiple correlation coefficient and Fisher-ratio statistics. The results of cross validation test using leave-one-out (Q2,0.956) and leave-two-out (Q2,0.953) methods showed good predictive ability of the models developed. Then, a single combined quantitative structure-retention relationship model, added temperature as a parameter, was also developed for all the temperatures, showing good statistical parameters (R=0.991 and F=728.474). The stability and validity of the combined model were verified by both internal (Q2>0.970) and external validation (Q=0.993) techniques. The results of the study indicated the efficiency of the classical topological descriptors in simultaneous prediction of retention index values of sulfur compounds at different temperatures. The topological descriptors well covered the molecular properties known to be relevant for gas chromatographic retention data, such as molecular size and degree of branching. [source] Volatile organic sulfur compounds in anaerobic sludge and sediments: Biodegradation and toxicityENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 12 2006Robin C. van Leerdam Abstract A variety of environmental samples was screened for anaerobic degradation of methanethiol, ethanethiol, propanethiol, dimethylsulfide, and dimethyldisulfide. All sludge and sediment samples degraded methanethiol, dimethylsulfide, and dimethyldisulfide anaerobically. In contrast, ethanethiol and propanethiol were not degraded by the samples investigated under any of the conditions tested. Methanethiol, dimethylsulfide, and dimethyldisulfide were mainly degraded by methanogenic archaea. In the presence of sulfate and the methanogenic inhibitor bromoethane sulfonate, degradation of these compounds coupled to sulfate reduction occurred as well, but at much lower rates. Besides their biodegradability, also the toxicity of methanethiol, ethanethiol, and propanethiol to methanogenesis with methanol, acetate, and H2/CO2 as the substrates was assessed. The 50% inhibition concentration of methanethiol on the methane production from these substrates ranged between 7 and 10 mM. The 50% inhibition concentration values of ethanethiol and propanethiol for the degradation of methanol and acetate were between 6 and 8 mM, whereas hydrogen consumers were less affected by ethanethiol and propanethiol, as indicated by their higher 50% inhibition concentration (14 mM). Sulfide inhibited methanethiol degradation already at relatively low concentrations: methanethioldegradation was almost completely inhibited at an initial sulfide concentration of 8 mM. These results define the operational limits of anaerobic technologies for the treatment of volatile organic sulfur compounds in sulfide-containing wastewater streams. [source] Quantitative Recovery of Elemental Sulfur and Improved Selectivity in a Chromium-Reducible Sulfur DistillationGEOSTANDARDS & GEOANALYTICAL RESEARCH, Issue 1 2009Jens Gröger soufre réductible par le chrome; CRS; soufre élémentaire; selectivité; efficacité de distillation Chromium-reducible sulfur (CRS) distillations are intended to recover only reduced inorganic sulfur compounds (RIS) including elemental sulfur. However, the quantitative recovery of elemental sulfur is not ensured in common CRS-distillations. The new method presented here was designed to remedy this deficiency. An increase in ethanol concentration assured the quantitative recovery of elemental sulfur in various forms and, in addition, all other RIS-compounds were quantitatively recovered. Furthermore, the selectivity of the procedure was improved by an additional filtration step to eliminate zinc particles from the Cr(II)-solution. Thus, the recovery of sulfates and organic sulfur compounds was significantly decreased by a factor of up to 35, depending on the compound analysed. Exhaustive testing with a variety of pure phases, rock and soil samples demonstrated the precision and accuracy of the new method. The new protocol eliminated the constraints of previous procedures. The improved distillation efficiency for elemental sulfur ensured the quantitative recovery of all RIS-compounds in a single-step distillation. Des distillations du soufre réductible par le chrome (CRS) ont été effectuées afin de récupérer uniquement les composés soufrés inorganiques (RIS: reduced inorganic sulfures) dont le soufre élémentaire. La procédure classique de distillation CRS ne permet pas néanmoins la récupération totale du soufre élémentaire. Une nouvelle méthode, présentée ici, a été développée pour remédier à ce problème. L'augmentation de la concentration en éthanol assure la récupération totale du soufre élémentaire sous différentes formes et, de plus, celle de tous les autres composés RIS. La sélectivité de la procédure a été améliorée par l'ajout d'une étape de filtration, qui élimine des particules de zinc provenant de la solution Cr(II). Ceci a entraîné une diminution jusqu'à un facteur 35 du taux d'extraction des sulfates et des composés soufrés organiques, selon les composés analysés. Des tests extensifs sur différentes phases pures et des échantillons de roches et de sols ont montré la précision et la justesse de cette nouvelle méthode. Le nouveau protocole élimine les contraintes des procédures passées. L'amélioration de l'efficacité de cette distillation concernant le soufre élémentaire garantit une récupération fiable de tous les composés RIS par une distillation en une seule étape. [source] Removal of H2S and volatile organic sulfur compounds by silicone membrane extractionJOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 1 2009I. Manconi Abstract BACKGROUND: This study explores an alternative process for the abatement and/or desulfurization of H2S and volatile organic sulfur compounds (VOSC) containing waste streams, which employs a silicone-based membrane to simultaneously remove H2S and VOSC. An extractive membrane reactor allows the selective withdrawal of VOSC and H2S simultaneously from the waste stream, while preventing direct contact between the waste stream and the absorbing solution and/or the biological treatment system. The influence of the sulfur compounds, membrane characteristics, extractant and pH was studied. RESULTS: Sulfide and the VOCS studied, i.e. methanethiol (MT), ethanethiol (ET) and dimethylsulfide (DMS) were removed from the synthetic wastewater using a silicone rubber membrane. Methanethiol showed the highest (8.72 × 10,6 m s,1) overall mass transfer coefficient (kov) and sulfide the lowest kov value (1.23 × 10,6 m s,1). Adsorption of the VOCS into the silicone membrane reduced the overall mass transfer coefficient. The kov when using Fe(III)EDTA, as extractant (5.81 × 10,7 m s,1) for sulfide extraction was one order of magnitude lower than with anaerobic water (2.54 × 10,6 m s,1). On the other hand, the sulfide removal efficiency with Fe(III)EDTA, was higher (84%) compared with anaerobic water (60%) as extractant. An additional mass transfer resistance was formed by elemental sulfur which remained attached to the membrane surface. CONCLUSIONS: Extraction of sulfide and VOCS from a synthetic wastewater solution through a silicone rubber membrane is a feasible process as alternative to the techniques developed to treat VOSC emissions. Optimizing the aqueous absorption liquid can increase the efficiency of extraction based processes. Copyright © 2008 Society of Chemical Industry [source] Use of Topological Indices of Organic Sulfur Compounds in Quantitative Structure-Retention Relationship StudyMOLECULAR INFORMATICS, Issue 9 2005F. Safa Abstract Structure-gas chromatographic retention index models were developed for some organic sulfur compounds at four different temperatures (60, 80, 100 and 120,°C) using only topological descriptors. At first, regression models were generated for each temperature separately with high values of multiple correlation coefficient and Fisher-ratio statistics. The results of cross validation test using leave-one-out (Q2,0.956) and leave-two-out (Q2,0.953) methods showed good predictive ability of the models developed. Then, a single combined quantitative structure-retention relationship model, added temperature as a parameter, was also developed for all the temperatures, showing good statistical parameters (R=0.991 and F=728.474). The stability and validity of the combined model were verified by both internal (Q2>0.970) and external validation (Q=0.993) techniques. The results of the study indicated the efficiency of the classical topological descriptors in simultaneous prediction of retention index values of sulfur compounds at different temperatures. The topological descriptors well covered the molecular properties known to be relevant for gas chromatographic retention data, such as molecular size and degree of branching. [source] Development of a novel process for the biological conversion of H2S and methanethiol to elemental sulfurBIOTECHNOLOGY & BIOENGINEERING, Issue 1 2003Jan Sipma Abstract The feasibility of anaerobic treatment of wastewater containing methanethiol (MT), an extremely volatile and malodorous sulfur compound, was investigated in lab-scale bioreactors. Inoculum biomass originating from full-scale anaerobic wastewater treatment facilities was used. Several sludges, tested for their ability to degrade MT, revealed the presence of organisms capable of metabolizing MT as their sole source of energy. Furthermore, batch tests were executed to gain a better understanding of the inhibition potential of MT. It was found that increasing MT concentrations affected acetotrophic organisms more dramatically than methylotrophic organisms. Continuous reactor experiments, using two lab-scale upflow anaerobic sludge bed (UASB) reactors (R1 and R2), aimed to determine the maximal MT load and the effect of elevated sulfide concentrations on MT conversion. Both reactors were operated at a hydraulic retention time (HRT) of about 7 hours, a temperature of 30°C, and a pH of between 7.3 and 7.6. At the highest influent MT concentration applied, 14 mM in R1, corresponding to a volumetric loading rate of about 50 mM MT per day, 87% of the organic sulfur was recovered as hydrogen sulfide (12.2 mM) and the remainder as volatile organic sulfur compounds (VOSCs). Upon decreasing the HRT to 3.5 to 4.0 h at a constant MT loading rate, the sulfide concentration in the reactor decreased to 8 mM and MT conversion efficiency increased to values near 100%. MT conversion was apparently inhibited by the high sulfide concentrations in the reactor. The specific MT degradation rate, as determined after 120 days of operation in R1, was 2.83 ± 0.27 mmol MT g VSS,1 day,1. During biological desulfurization of liquid hydrocarbon phases, such as with liquefied petroleum gas (LPG), the combined removal of hydrogen sulfide and MT is desired. In R2, the simultaneous addition of sodium sulfide and MT was therefore studied and the effect of elevated sulfide concentrations was investigated. The addition of sodium sulfide resulted in enhanced disintegration of sludge granules, causing significant washout of biomass. Additional acetate, added to stimulate growth of methanogenic bacteria to promote granulation, was hardly converted at the termination of the experimental period. © 2003 Wiley Periodicals, Inc. Biotechnol Bioeng 82: 1,11, 2003. [source] Sulfur-Selective Desulfurization of Dibenzothiophene and Diesel Oil by Newly Isolated RhodococcuserythropolisNCC-1CHINESE JOURNAL OF CHEMISTRY, Issue 3 2007Yu-Guang Li Abstract A dibenzothiophene (DBT)-desulfurizing bacteria strain was isolated from oil-contaminated soils and identified as Rhodococcuserythropolis NCC-1. Strain NCC-1 was found to convert DBT to hydroxybiphenyl (2-HBP) via the 4S pathway and also be able to use organic sulfur compounds other than DBT as a sole sulfur source. The strain could desulfurize 4,6-dimethyldibenzothiophene (4,6-DMDBT), which is one of the most recalcitrant dibenzothiophene derivatives to hydrodesulfurization. When two type of oils, a model oil [n -hexadecane (n -C16) containing DBT] and a hydrodesulfurized diesel oil with various organic sulfur compounds, were treated with Rhodococcuserythropolis NCC-1 cells, the total sulfur content significantly decreased, from 150 to 20 mg/L for n -C16 and from 554 to 274 mg/L for diesel oil. The newly isolated strain NCC-1 is considered to have good potential for application in the biodesulfurization of fossil fuels. [source] | |||||||||||||