Sulfide formation

Various patents (22—24) have been issued claiming the use of tetrakis(hydroxymethyl)phosphonium sulfate in, for example, water treating, pharmaceuticals (qv), and in the oil industry where this compound shows exceptional activity toward the sulfate-reducing bacteria that are a primary cause of hydrogen sulfide formation and consequent problems associated with souring and corrosion (25). 

Shipment nd Stora.ge, Sulfur monochloride is minimally corrosive to carbon steel and iron when dry. If it is necessary to avoid discoloration caused by iron sulfide formation or chloride stress cracking, 310 stainless steel should be used. Sulfur monochloride is shipped in tank cars, tank tmcks, and steel dmms. When wet, it behaves like hydrochloric acid and attacks steel, cast iron, aluminum, stainless steels, copper and copper alloys, and many nickel-based materials. Alloys of 62 Ni—28 Mo and 54 Ni—15 Cr—16 Mo are useful under these conditions. Under DOT HM-181 sulfur monochloride is classified as a Poison Inhalation Hazard (PIH) Zone B, as well as a Corrosive Material (DOT Hazard Class B). Shipment information is available (140). 

Adhesives in the Tire Industry. Cobalt salts are used to improve the adhesion of mbber to steel. The steel cord must be coated with a layer of brass. During the vulcanization of the mbber, sulfur species react with the copper and zinc in the brass and the process of copper sulfide formation helps to bond the steel to the mbber. This adhesion may be further improved by the incorporation of cobalt soaps into the mbber prior to vulcanization (53,54) (see Tire cords). 

Sulfur Corrosion Chromium is the most important material in imparting resistance to sulfidation (formation of smfidic scales similar to oxide scales). The austenitic alloys are generally used because of their superior mechanical properties and fabrication qualities, despite the fact that nickel in the alloy tends to lessen resistance to sulfidation somewhat. 

The influence of Zn-deposition on Cu(lll) surfaces on methanol synthesis by hydrogenation of CO2 shows that Zn creates sites stabilizing the formate intermediate and thus promotes the hydrogenation process [2.44]. Further publications deal with methane oxidation by various layered rock-salt-type oxides [2.45], poisoning of vana-dia in VOx/Ti02 by K2O, leading to lower reduction capability of the vanadia, because of the formation of [2.46], and interaction of SO2 with Cu, CU2O, and CuO to show the temperature-dependence of SO2 absorption or sulfide formation [2.47]. 

Goodfellow, W.D. and Blaise, B. (1988) Sulfide formation and hydrothermal alteration of hemipelagic sediment in Middle Valley, northern Juan de Fuca Ridge. Can. Mineral, 26, 675-696. 

Major problems in oil and gas operations result from the biogenic formation of hydrogen sulfide (H2S) in the reservoir. The presence of H2S results in increased corrosion, iron sulfide formation, higher operating costs, and reduced revenue and constitutes a serious environmental and health hazard. 

The effects of tin/palladium ratio, temperatnre, pressnre, and recycling were studied and correlated with catalyst characterization. The catalysts were characterized by chemisorption titrations, in situ X-Ray Diffraction (XRD), and Electron Spectroscopy for Chemical Analysis (ESCA). Chemisorption studies with hydrogen sulfide show lack of adsorption at higher Sn/Pd ratios. Carbon monoxide chemisorption indicates an increase in adsorption with increasing palladium concentration. One form of palladium is transformed to a new phase at 140°C by measurement of in situ variable temperature XRD. ESCA studies of the catalysts show that the presence of tin concentration increases the surface palladium concentration. ESCA data also indicates that recycled catalysts show no palladium sulfide formation at the surface but palladium cyanide is present. 

The last reaction perhaps involves an intermediate such as 33a which expells a proton and dimethyl sulfide. Formation of the Schiff s base with t-butylamine, reduction with sodium borohydride and hydrogenolysis of the benzyl ether produces sulfonterol (28). Despite the fact that the methylene hydrogen of sulfonterol must be much less acidic than of the corresponding urea proton on carbuterol or the sulfonamide proton on soterenol, good bioactivity is retained. 

Hydrogen sulfide formation has been demonstrated in pediatric intravenous amino acid solutions used to treat infants with high protein requirements (Decsi and Koletzko 1993). Levels up to 1.96 ppm were found, presumably formed by sulfide liberation from cysteine derivatives during heat sterilization. 

Peroxynitrite easily oxidizes nonprotein and protein thiyl groups. In 1991, Radi et al. [102] have shown that peroxynitrite efficiently oxidizes cysteine to its disulfide form and bovine serum albumin (BSA) to some derivative of sulfenic acid supposedly via the decomposition to nitric dioxide and hydroxyl radicals. Pryor et al. [124] suggested that the oxidation of methionine and its analog 2-keto-4-thiomethylbutanic acid occurred by two competing mechanisms, namely, the second-order reaction of sulfide formation and the one-electron... 

In-sewer processes, e.g., hydrogen sulfide formation and fermentation, may cause corrosion, toxicity, and odor problems. 

Metcalf and Eddy, Inc. (1991), Wastewater Engineering — Treatment, Disposal and Reuse, 3rd edition revised by G. Tchobanoglous and F. L. Burton, McGraw-Hill, Inc., New York, p. 1334. Nielsen, P.H. and T. Hvitved-Jacobsen (1988), Effect of sulfate and organic matter on the hydrogen sulfide formation in biofilms of filled sanitary sewers, J. Water Pol. Contr. Fed., 60(5), 627-634. 

Anaerobic Processes — Sulfide Formation and Integrated Modeling... 

These two examples show the worldwide importance and the complexity of sulfide formation in sewers. 

Example 6.2 Hydrogen sulfide formation in a pressure main... 

The volumetric rate of hydrogen sulfide formation in each of the two pipes multiplied with the residence time gives the hydrogen sulfide concentration in the wastewater at the outlet ... 

Basic Aspects and Stoichiometry of Hydrogen Sulfide Formation... 

To establish the stoichiometry of the sulfide formation, Equation (6.3) must be combined with the oxidation process for the organic matter that is the actual electron donor for the heterotrophic sulfate-reducing bacteria. The procedure for the combination of the oxidation and the reduction process steps is the same as outlined in Section 2.1.3. If organic matter is considered simply as CH20, the combination of the oxidation process as depicted in Example 2.2 and the reduction reaction for sulfate shown in Equation (6.3) result in the following redox process ... 

Sulfate is typically found in all types of wastewater in concentrations greater than 5-15 gS nr i.e., in concentrations that are not limiting for sulfide formation in relatively thin biofilms (Nielsen and Hvitved-Jacobsen, 1988). In sewer sediments, however, where sulfate may penetrate the deeper sediment layers, the potential for sulfate reduction may increase with increasing sulfate concentration in the bulk water phase. Under specific conditions, e.g., in the case of industrial wastewater, it is important that oxidized sulfur components (e.g., thiosulfate and sulfite) other than sulfate may act as sulfur sources for sulfate-reducing bacteria (Nielsen, 1991). 

The temperature dependency of the sulfate reduction rate for single sulfate-reducing bacteria is high, corresponding to a temperature coefficient, a, of about 1.13, i.e., a change in the rate with a factor Q10 = 3.4 per 10°C of temperature increase. Because diffusion of substrate into biofilms or sediments is typically limiting sulfide formation, the temperature coefficient is reduced to about... 

The potential production of sulfide depends on the biofilm thickness. If the flow velocity in a pressure main is over 0.8-1 ms-1, the corresponding biofilm is rather thin, typically 100-300 pm. However, high velocities also reduce the thickness of the diffusional boundary layer and the resistance against transport of substrates and products across the biofilm/water interphase. Totally, a high flow velocity will normally reduce the potential for sulfide formation. Furthermore, the flow conditions affect the air-water exchange processes, e.g., the emission of hydrogen sulfide (cf. Chapter 4). 

The anaerobic residence time of the wastewater during transport is a factor that affects the level of sulfide concentration in the wastewater. The residence time in a pressure pipe is determined by the magnitude of wastewater inflow compared with the volume (length and diameter) of the pipe. The level of sulfide formation in a given pipe is subject to the diurnal variation of the inflowing... 

The first term in Equation (6.8) is basically equal to Equation (3) in Table 6.1, and thereby corresponds to the formation rate of sulfide. However, the areal sulfide formation rate is normally found to be lower in a gravity sewer than in a pressure main, probably because of the effects of the daily changing water level and flow conditions. The value of M is therefore typically lower than shown in Equation (3). Pomeroy and Parkhurst propose M =0.3210-3 m h-1. 

Focusing on sulfide formation, the sediment is often simply taken into account by considering it covered with a biofilm. The potential for sulfide production in terms of the surface flux will typically exceed what is observed for sewer biofilms, e.g., being 50-100% higher (Schmitt and Seyfried, 1992 Bjerre et al., 1998). 

A reliable concrete corrosion rate is difficult to predict. As already mentioned and also shown in Figure 4.4, it requires that several process and exchange rates in terms of primarily sulfide formation, emission to the sewer atmosphere, sulfide absorption and sulfide oxidation on the sewer walls can be determined. 

The concrete sewer network or pumping station that is considered is located downstream of systems with risk for a high sulfide formation. Such systems may primarily include pressure mains and also gravity sewers with permanent deposits of sewer solids. 

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