Interactions occurring between halide ions and aqueous ammonia under ultra violet light with low pressure mercury lamps.
Item
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Title
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Interactions occurring between halide ions and aqueous ammonia under ultra violet light with low pressure mercury lamps.
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Identifier
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AAI3245094
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identifier
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3245094
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Creator
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Beckles, Yvette.
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Contributor
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Adviser: Vasil Diyamandoglu
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Date
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2007
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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, Civil
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Abstract
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Ultraviolet (UV) technology is currently applied as a viable alternative in drinking water and wastewater applications, namely: disinfection and advanced oxidation processes (AOP). Nevertheless, little is known about the interactions that may occur between indigenous water constituents when exposed to UV irradiation. Such interactions may occur as secondary reactions, resulting in changes to effluent streams that might not meet mandatory regulations.;The indigenous water constituents investigated in this research included the interactions of individual halide ions, i.e. bromide (Br-) chloride (Cl-) and iodide (I-) with ammonia (NH3). The findings revealed that Br- and Cl - promote ammonia photo-oxidation in both acidic (pH 5) and alkaline (pH 8--10) solutions. I- was unable to enhance the oxidation of ammonia. The solution pH and oxygen concentration were depressed during ammonia oxidation while the halide ion concentrations remained unchanged. The extent to which halide ions were able to augment ammonia oxidation was found to be dependent on the type and concentration of the halide ion, as well as the initial solution pH. Nitrite (NO2-) and nitrate (NO3-) were produced as the major final stable products with the yields being associated with the solution pH during the irradiation. Bromate (BrO3-) and sulfur hexafluoride (SF6) were used as electron (e -) scavengers to demonstrate that e- may be scavenged from the Charge Transfer to Solvent (CTTS) state of halide ions and that during ammonia photo-oxidation, e- are generated.;Irradiation of a wastewater sample spiked with ammonia and its pH adjusted to 10 showed that ammonia oxidation in the presence of halide ions (chloride) occurs simultaneously with TOC degradation by UV irradiation. Approximately 30% of both TOC and ammonia degraded after 360 minutes of irradiation, while approximately 88% of the dissolved oxygen was consumed after 120 minutes of irradiation. Nitrite and nitrate were formed in the irradiating solution.;A reaction scheme proposed for the NH3/Cl- system and simulation of the reactions, demonstrated that the scavenging of electrons from the CTTS state of irradiated halide ions, forming an additional supply of hydroxyl (OH) and superoxide (O2-) radicals in solution was responsible for the enhanced rate of NH3 oxidation observed.
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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.
