Sulfide, oxidation

Manganese dioxide Aluminum, hydrogen sulfide, oxidants, potassium azide, hydrogen peroxide, peroxosulfuric acid, sodium peroxide... 

Fig. 4. Schematic of a leather tanning faciUty fitted with a wastewater treatment plant. Treatment of the combined wastes using sulfide oxidation and waste effluent pH adjustment greatiy decreases the suspended soHds and BOD loading (3). Courtesy of Krieger Publishing Co.

The toxic nature of mercury and its compounds has caused concern over environmental pollution, and governmental agencies have imposed severe restrictions on release of mercury compounds to waterways and the air (see Mercury). Methods of precipitation and agglomeration of mercurial wastes from process water have been developed. These methods generally depend on the formation of relatively insoluble compounds such as mercury sulfides, oxides, and thiocarbamates. MetaUic mercury is invariably formed as a by-product. The use of coprecipitants, which adsorb mercury on their surfaces facihtating removal, is frequent. 

Direct l eaching of Concentrates. Sherri tt Gordon Mines, Ltd., has adapted the process first used on nickel sulfide ores to zinc sulfide oxidation with air in aqueous slurry under pressure (42,43). The concentrates are leached direcdy with return acid from the cells and the sulfide is converted to free sulfur ... 

The more soluble forms of barium such as the carbonate, chloride, acetate, sulfide, oxide, and nitrate, tend to be more acutely toxic (50). Mean lethal doses for ingested barium chloride were 300—500 mg/kg in rats and 7—29 mg/kg in mice (47). 

Like ammonia, hydrogen sulfide (oxid. no. S = —2) can act only as a reducing agent when it takes part in redox reactions. Most often the H2S is oxidized to elementary sulfur, as in the reaction... 

When N-sulfinylaziridine-2-carboxylate 242 (Scheme 3.89) was treated with LAH, followed by N-acetylation and sulfide oxidation, (+)-thiamphenicol (243) was isolated in 72 % yield [63], Thiamphenicol is a broad-spectrum synthetic antibacter-... 

The flotation of sulfidic, oxidic, and salt-type ores and, in special cases, silicate ores can be improved by the use of ether carboxylates as collectors [221,222]. In particular, the flotation of fluorite, barite, and scheelite is mentioned. Special synergistic combinations of ether carboxylates with fatty acids [223] and with vinyl- or alkylsulfonic acid polymer [224] are described. 

What are the relative contributions of these two sources Two approaches have been taken. One is to establish the geology and hydrology of a basin in great detail. This has been carried out for the Amazon (Stallard and Edmond, 1981) with the result that evaporites contribute about twice as much sulfate as sulfide oxidation. The other approach is to apply sulfur isotope geochemistry. As mentioned earlier, there are two relatively abundant stable isotopes of S, and The mean 34/32 ratio is 0.0442. However, different source rocks have different ratios, which arise from slight differences in the reactivities of the isotopes. These deviations are expressed as a difference from a standard, in the case of sulfur the standard being a meteorite found at Canyon Diablo, Arizona. 

It was concluded from this and related works that suppression of the photodissolution of n-CdX anodes in aqueous systems by ions results primarily from specific adsorption of X at the electrode surface and concomitant shielding of the lattice ions from the solvent molecules, rather than from rapid annihilation of photogenerated holes. The prominent role of adsorbed species could be illustrated, by invoking thermodynamics, in the dramatic shift in CdX dissolution potentials for electrolytes containing sulfide ions. The standard potentials of the relevant reactions for CdS and CdSe, as well as of the sulfide oxidation, are compared as follows (vs. SCE) [68] ... 

Other asymmetric sulfide oxidation methods (a) Bolm, C. and Bienewald, F. (1995) Angew. Chem. Int. Ed., 34, 2640 ... 

See Hydrazine and derivatives, above Hydrogen sulfide Oxidants Non-metal hydrides, above Potassium phosphinate Air, or Nitric acid Sulfur dioxide, below... 

During preparations for blasting the sulfide mineral copper pyrites, ammonium nitrate-based blasting cartridges exploded prematurely in the blast holes. This was attributed to exothermic interaction of acid ground-water with the sulfide-oxidant combination. 

Hydrogen peroxide Metals, Metal oxides, Metal salts Hydrogen sulfide Oxidants... 

Regarding the conditions for the biological oxidation, the optimum pH is in the range of 7-9, temperature of about 30°C, nutrients supply and the electric conductivity of the washing liquid must be kept between 30 and lOOmS/cm. In general, neutrophilic sulfide-oxidizing cultures of Thiobacillus species can be used, especially T. denitrificans. 

In the biotechnological arena, a process for removing H2S and mercaptans from a hydrocarbon stream, such as a LPG, was disclosed [171]. Sulfide oxidizing microorganisms, such as those from the genera Thiobacillus and Thiomicrospira, are employed to convert H2S to sulfur and mercaptans to disulfides. First a weakly basic stream, (e.g., a sodium bicarbonate solution) is used to extract the sulfur molecules from the hydrocarbon stream using an ordinary extraction column. The extracted sulfur molecules are then... 

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