Application of unmodified activated carbon for removal of odor from wastewater treatment facilities.
Item
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Title
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Application of unmodified activated carbon for removal of odor from wastewater treatment facilities.
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Identifier
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AAI9986296
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identifier
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9986296
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Creator
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Adib, Foad.
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Contributor
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Advisers: Reza M. Khanbilvardi | Teresa J. Bandosz
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Date
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2000
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Language
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English
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Publisher
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City University of New York.
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Subject
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Engineering, Environmental | Engineering, Sanitary and Municipal | Engineering, Civil
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Abstract
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Unmodified activated carbons (UAC) can be used to effectively remove H2S, as the leading malodorant, from the air streams at the wastewater treatment facilities. Upon adsorption in pores of UAC, H2S is immobilized through oxidation by oxygen to more stable elemental sulfur or sulfuric acid, which deposit in the pores of carbon. The general mechanism for the process includes initial chemisorption of both oxygen and hydrogen sulfide on the surface of carbon and the following surface reaction between the adsorbed species. Presence of a high level of humidity in the influent is a necessary condition for the process. The reactions take place in a thin film of water that forms inside the pores of carbon and serves as the reaction medium.;The surface pH of carbon has a dominant effect on the process. Unlike molecular H2S, hydrosulfide ion can be easily oxidized. A pH value around 4.5, which is only high enough for mild dissociation of H2S, is sufficient for its effective removal. The effect of pore structure is not as vivid as surface chemistry in the performance of carbons, but carbons with higher pore volume, especially microporous volume, provide more removal capacity.;Oxidized carbons, despite their lower capacities, show a higher selectivity toward formation of sulfuric acid than UACs. Similar effect is observed when nitrogen is incorporated into the carbon. Nearly all of sulfuric acid and a lot of sulfur radical content can be removed by washing at ambient temperature. Oxidized carbons provide a benefit of oxidation-during-washing of the sulfur radicals whereas UACs generally give way to the formation of bulky insoluble polysulfides. The latter will permanently deposit in the pores and can not be removed by simple methods.;A rate expression is provided for the process based on the Langmuir-Hinshelwood surface reaction model. Sulfur deposition is introduced to the rate expression as the fouling factor and an expression is derived based on the initial rate of the reaction and the square of available sites. The model can effectively predict the performance of carbon and can be used to design a bed of carbon to withstand a certain situation.
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Type
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dissertation
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Source
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PQT Legacy CUNY.xlsx
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degree
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Ph.D.
