Sulfate, activation from elemental sulfur

NKK s Bio-SR process is another iron-based redox process which instead of chelates, uses Thiobacillusferroidans )2iQ. - 2i to regenerate the solution (9). This process absorbs hydrogen sulfide from a gas stream into a ferric sulfate solution. The solution reacts with the hydrogen sulfide to produce elemental sulfur and ferrous sulfate. The sulfur is separated via mechanical means, such as filtering. The solution is regenerated to the active ferric form by the bacteria. 

The chemical composition of particulate pollutants is determined in two forms specific elements, or specific compounds or ions. Knowledge of their chemical composition is useful in determining the sources of airborne particles and in understanding the fate of particles in the atmosphere. Elemental analysis yields results in terms of the individual elements present in a sample such as a given quantity of sulfur, S. From elemental analysis techniques we do not obtain direct information about the chemical form of S in a sample such as sulfate (SO/ ) or sulfide. Two nondestructive techniques used for direct elemental analysis of particulate samples are X-ray fluorescence spectroscopy (XRF) and neutron activation analysis (NAA). 

The element sulfur occurs in the two protein amino acids, cysteine and methionine. Plants, unlike animals, synthesize these two amino acids using inoiganic sulfur (present principally as sulfate in most aerobic soils) as a sulfur source. Thus, the formation of the sulfur amino acids by plants is of considerable importance, not only because of its intrinsic interest as a plant activity but also bemuse a supply of sulfur amino adds from plants (either directly or indirectly) is essential for human health and nutrition. Moreover, in some plant foodstu, espedally legumes, the sulfur amino adds are present in such low amounts that they hmit the availabihty of the protein. This is of special concern in some developing countries in which plant foodstuffs comprise the bulk of the food intake. 

Like pesticides, heavy metals are traditionally tested by enzyme inhibition or modulation of catalytic activity. Several metalloproteins behave as chelators for specific metals with no known catalytic reactions. Such heavy metal binding sites exist in metallothioneins and in various protein elements of bacterial heavy metal mechanisms and have been exploited for specific detection through affinity events. Nevertheless and as previously mentioned, bacterial resistance mechanisms can also be linked to catalytic pathways. For instance, c5rtochromes c3 and hydrogenases from sulfate and sulfur reducing bacteria [284,285] are well suited for bioremediation purposes because they can reduce various metals such as U(V) and Cr(VI) [286,287]. Cytochrome c3 has been reported to catalyse Cr(VI) and U(VI) reduction in Desulfovibrio vulgaris [288,289], suggesting... 

World sulfur reserves. The earth s crust contains about 0.6% S, where it occurs as elemental S (brimstone) in deposits associated with gypsum and calcite combined S in metal sulfide ores and mineral sulfates as a contaminant in natural gas and crude oils as pyritic and organic compounds in coal and as organic compounds in tar sands (Tisdale and Nelson, 1966). The elemental form commonly occurs near active or extinct volcanoes, or in association with hot mineral spings. Estimates by Holser and Kaplan (1966) of the terrestrial reservoirs of S suggest that about 50% of crustal S is present in relatively mobile reservoirs such as sea water, evaporites, and sediments. The chief deposits of S in the form of brimstone and pyrites are in Western European countries, particularly in France, Spain, Poland, Japan, Russia, U.S.A., Canada, and Mexico. World production of S in the form of brimstone and pyrites was approximately 41 Tg in 1973 other sources accounted for about 8 Tg, making a total of 49 Tg (Anon, 1973). Byproduct S from sour-gas, fossil fuel combustion, and other sources now accounts for over 50% of S used by western countries, as shown in Fig. 9.1. This percentage may increase as pollution abatement measures increase the removal of SO2 from fossil fuel, particularly in the U.S.A. Atmospheric S, returned to the earth in rainwater, is also a very important source of S for plants. 

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