Sulfate sediment

Peck, M.R., Klessa, D.A. and Baird, D.J. (2002) A tropical sediment toxicity test using the dipteran Chironomus crassiforceps to test metal bioavailability with sediment pH change in tropical acid-sulfate sediments, Environmental Toxicology and Chemistry 21 (4), 720-728. 

Pretreatment steps before extraction include drying of the sample, which can be performed as air-drying, freeze-drying, or drying by mixing the sample with sodium sulfate. Sediment samples have been air-dried or freeze-dried before extraction [33,113-115]. 

G58. Rogozovskaya, M.Z., N.K. Luk yanova, T.I. Konochuk, "The properties of the calcium sulfate sediment formed in brine treatment for the production of chlorine", Khim. prom., v9, 10, pp770-772 (1977)... 

Authigenic barium sulfate or barite [13462-86-7] is found in relatively high concentrations in sediments covering active diverging oceanic plate boundaries. It occurs as rounded masses containing up to 75% BaSO or as a dispersed constituent of the sediment. Its origins are uncertain, but it is likely that it is associated with hydrothermal actions. 

Iron oxide yellows can also be produced by the direct hydrolysis of various ferric solutions with alkahes such as NaOH, Ca(OH)2, and NH. To make this process economical, ferric solutions are prepared by the oxidation of ferrous salts, eg, ferrous chloride and sulfate, that are available as waste from metallurgical operations. The produced precipitate is washed, separated by sedimentation, and dried at about 120°C. Pigments prepared by this method have lower coverage, and because of their high surface area have a high oil absorption. 

Strontium Sulfate. Strontium sulfate, SrSO, occurs as celestite deposits in beds or veins in sediments or sedimentary rocks. Celestite has a specific gravity of ca 3.97, a Mohs hardness of 3.0—3.5, and is colodess-to-yeUow and often pale blue. Strontium sulfate forms colorless or white rhombic crystals with a specific gravity of 3.96 and an index of refraction of 1.622—1.631. It decomposes at 1580°C and has a solubiUty of 0.0113 g per 100 mL of water at 0°C. 

These bacteria are anaerobic. They may survive but not actively grow when exposed to aerobic conditions. They occur in most natural waters including fresh, brackish, and sea water. Most soils and sediments contain sulfate reducers. Sulfate or sulfite must be present for active growth. The bacteria may tolerate temperatures as high as about 176°F (80°C) and a pH from about 5 to 9. 

Coagulation involves the addition of chemicals to alter the physical state of dissolved and suspended solids. This facilitates their removal by sedimentation and filtration. The most common primary coagulants are alum ferric sulfate and ferric chloride. Additional chemicals that may be added to enhance coagulation include activate silica, a complex silicate made from sodium silicate, and charged organic molecules called polyelectrolytes, which include large-molecular-weight polyacrylamides, dimethyl-diallylammonium chloride, polyamines, and starch. 

In sedimentation the water to be treated flows slowly through a tank, allowing the suspended material in the water to fall to the base of the tank. The use of coagulating compounds, such as aluminum and ferric sulfate, increases the efficiency. 

If the water is permanently hard due to MgS04, and lime is added, the precipitates calcium sulfate, CaS04, and magnesium hydroxide, Mg(OH)4, result, which are removed by sedimentation. 

Permanent hardness can also be due to the presence of CaS04, in which case the addition of soda (sodium carbonate), NaiC03, produces sodium sulfate, Na2S04, and calcium carbonate, CaCO, this precipitate once again is removed by sedimentation. 

Precipitation involves the alteration of the ionic equilibrium to produce insoluble precipitates. To remove the sediment, chemical precipitation is allied with solids separation processes such as filtration. Undesirable metal ions and anions are commonly removed from waste streams by converting them to an insoluble form. The process is sometimes preceded by chemical reduction of the metal ions to a form that can be precipitated more easily. Chemical equilibrium can be affected by a variety of means to change the solubility of certain compounds. For e.xample, precipitation can be induced by alkaline agents, sulfides, sulfates, and carbonates. Precipitation with chemicals is a common waste stream treatment process and is effective and reliable. The treatment of sludges is covered next. 

The purple protein is reddish in solutions and purple in the ammonium sulfate precipitate. The molecular weight is 39,000 by the sedimentation equilibrium method. The purple protein is brightly red-fluorescent, but the fluorescence characteristics cannot be related to the luminescence of Latia (Fig. 6.1.5 Shimomura and Johnson, 1968c). 

Dissimilatory sulfate reducers such as Desul-fovibrio derive their energy from the anaerobic oxidation of organic compounds such as lactic acid and acetic acid. Sulfate is reduced and large amounts of hydrogen sulfide are generated in this process. The black sediments of aquatic habitats that smell of sulfide are due to the activities of these bacteria. The black coloration is caused by the formation of metal sulfides, primarily iron sulfide. These bacteria are especially important in marine habitats because of the high concentrations of sulfate that exists there. 

The case of bacterial reduction of sulfate to sulfide described by Berner (1984) provides a useful example. The dependence of sulfate reduction on sulfate concentration is shown in Fig. 5-4. Here we see that for [SO ] < 5 mM the rate is a linear function of sulfate concentration but for [SO4 ] > 10 itiM the rate is reasonably independent of sulfate concentration. The sulfate concentration in the ocean is about 28 mM and thus in shallow marine sediments the reduction rate does not depend on sulfate concentration. (The rate does depend on the concentration of organisms and the concentration of other necessary reactants - organic carbon in this case.) In freshwaters the sulfate concentration is... 

Sediments Dry with sodium sulfate extract with acetone/methylene chloride concentrate GC/FPD No data 73-95 Belisle and Swineford 1988... 

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