Hydrogen sulfide, potential

Corrosion protection is indispensable, especially concerning certain vulnerable parts of the aircraft such as the combustion chamber and turbine. The potential hazards are linked to the presence of sulfur in various forms mercaptans, hydrogen sulfide, free sulfur, and sulfides. 

Conversion Processes. Most of the adsorption and absorption processes remove hydrogen sulfide from sour gas streams thus producing both a sweetened product stream and an enriched hydrogen sulfide stream. In addition to the hydrogen sulfide, this latter stream can contain other co-absorbed species, potentially including carbon dioxide, hydrocarbons, and other sulfur compounds. Conversion processes treat the hydrogen sulfide stream to recover the sulfur as a salable product. 

Potential Processes. Sulfur vapor reacts with other hydrocarbon gases, such as acetjiene [74-86-2] (94) or ethylene [74-85-1] (95), to form carbon disulfide. Higher hydrocarbons can produce mercaptan, sulfide, and thiophene intermediates along with carbon disulfide, and the quantity of intermediates increases if insufficient sulfur is added (96). Light gas oil was reported to be successflil on a semiworks scale (97). In the reaction with hydrocarbons or carbon, pyrites can be the sulfur source. With methane and iron pyrite the reaction products are carbon disulfide, hydrogen sulfide, and iron or iron sulfide. Pyrite can be reduced with carbon monoxide to produce carbon disulfide. 

Similar to the pH meter, gas meters employ specific ion electrodes. The electrodes generate a potential proportional to the activity of a specific ion in solution. The calibration is achieved in standard solution and results read in mV or concentration in mg/L or ppm on the meter. The water can be adapted to monitor the concentration of carbon dioxide, hydrogen sulfide, ammonia, chloride, calcium, potassium and sodium to name a few. 

Fig. 2.2 Potential-pH diagram for the stable equilibria of the system sulfur-water at 25 °C (gaseous hydrogen sulfide is designated in italic letters) (Reproduced from [3], Copyright NACE International 2010)...

This new method can eliminate the potential hazard of excess sulfide in the effluent and the formation of gaseous hydrogen sulfide. In operation, the FeS is added to wastewater to supply sufficient sulfide ions to precipitate metal sulfides that have lower solubilities than FeS. Typical reactions include the following51-62 ... 

Male Wistar rats were administered 330 or 660 mg/kg of ethanol intraperitoneally 30 minutes before being exposed to 800 ppm of hydrogen sulfide for a maximum of 20 minutes, which was a potentially fatal hydrogen sulfide exposure (Beck et al. 1979). Mean times to unconsciousness in animals that were exposed to hydrogen sulfide with ethanol pretreatment at either of these dose levels were approximately 35% less than times to unconsciousness without ethanol pretreatment (Beck et al. 1979). The clinical relevance of these findings, which used potentially fatal doses of both ethanol and hydrogen sulfide, is unclear. 

As hydrogen sulfide is a neurotoxic agent, an inhalation study examining potential developmental neurotoxicity is needed. Such studies should include a battery of tests to examine the function of the nervous system in the offspring of animals exposed to hydrogen sulfide during gestation or for various periods before adulthood. 

Effect. Potential biomarkers of the subclinical effects of hydrogen sulfide are decreases in the activities of the heme synthesis enzymes, ALA-S and Haem-S (Jappinen and Tenhunen 1990). These effects have nothing to do with the mechanism of toxicity, however. Neurological indices are also used as biomarkers of effect for hydrogen sulfide (Gaitonde et al. 1987 Kilbum 1993 Stine et al. 1976 Tvedt et al. 1991b). 

Reliable evaluation of the potential for human exposure to hydrogen sulfide depends in part on the reliability of supporting analytical data from environmental samples and biological specimens. In reviewing data on hydrogen sulfide levels monitored or estimated in the environment, it should also be noted that the amount of chemical identified analytically is not necessarily equivalent to the amount that is bioavailable. 

Exposure Levels in Humans. Occupational studies often do not report exposure levels. Additional information is needed on the exposure levels among populations living in the vicinity of hazardous waste sites and other potential sources of hydrogen sulfide, such as hot springs and waste water treatment plants. 

Braunstein H, Tomasulo M. 1978. Hydrogen sulfide-producing Cilrobacler diversus. A re-emphasis of the potential ability of all Enterobacteriaceae to manifest this quality. Am J Clin Pathol 69 418-420. 

Lewis Bases. A variety of other ligands have been studied, but with only a few of the transition metals. There is still a lot of room for scoping work in this direction. Other reactant systems reported are ammoni a(2e), methanol (3h), and hydrogen sulfide(3b) with iron, and benzene with tungsten (Tf) and plati num(3a). In a qualitative sense all of these reactions appear to occur at, or near gas kinetic rates without distinct size selectivity. The ammonia chemisorbs on each collision with no size selective behavior. These complexes have lower ionization potential indicative of the donor type ligands. Saturation studies have indicated a variety of absorption sites on a single size cluster(51). 

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