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Effects of Nitrite, Nitrate, and Humic Acid on the Photodegradation of Dimethyl, Diethyl, and Dipropyl Phthalic Acid Ester.

Record Type:	Electronic resources : Monograph/item
Title/Author:	Effects of Nitrite, Nitrate, and Humic Acid on the Photodegradation of Dimethyl, Diethyl, and Dipropyl Phthalic Acid Ester./
Author:	Lu, Xiaofei.
Published:	Ann Arbor : ProQuest Dissertations & Theses, : 2020,
Description:	210 p.
Notes:	Source: Dissertations Abstracts International, Volume: 81-12, Section: B.
Contained By:	Dissertations Abstracts International81-12B.
Subject:	Analytical chemistry. -
Online resource:	http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=27960094
ISBN:	9798641709772

Effects of Nitrite, Nitrate, and Humic Acid on the Photodegradation of Dimethyl, Diethyl, and Dipropyl Phthalic Acid Ester.
Lu, Xiaofei.

Effects of Nitrite, Nitrate, and Humic Acid on the Photodegradation of Dimethyl, Diethyl, and Dipropyl Phthalic Acid Ester. - Ann Arbor : ProQuest Dissertations & Theses, 2020 - 210 p.

Source: Dissertations Abstracts International, Volume: 81-12, Section: B.

Thesis (Ph.D.)--University of Massachusetts Lowell, 2020.

This item must not be sold to any third party vendors.

Phthalic Acid Esters (PAEs) have been intensively used in the manufacturing of plastics and other products. During the whole life cycle of these products, PAEs can be readily released into the environment and pose risks to public health and the ecosystem because of their reproductive and developmental toxicity, carcinogenicity, and chronic organ toxicity to human and wildlife. Knowledge on the occurrence, behavior, and fate of PAEs in the environment is essential for assessing the risk and making policies to control the PAEs. Photodegradation studies of PAEs were conducted in this study to elucidate the behavior and fate of PAEs in the environment.A LC-MS/MS method was developed at first to quantify and identify the PAEs and their photodegradation intermediate products. LC mobile phase conditions including type of organic solvent, organic solvent content, and flow rate were evaluated to find out the best combination for separation and quantitation purposes. Effects of Electrospray Ionization (ESI) parameters including capillary voltage, sampling cone voltage, extraction cone voltage, source temperature, desolvation temperature, cone gas flow rate, and desolvation gas flow rate on the ionization efficiency were systematically investigated and optimized using One-Variable-at-A-Time (OVAT) strategy. The optimized LC-MS/MS method was used to identify and quantify the photodegradation intermediate products of PAEs. The direct photodegradation of Dimethyl Phthalate (DMP), Diethyl Phthalate (DEP), and Dipropyl Phthalate (DPP) were conducted under UV and solar irradiation. Under UV irradiation, the photodegradation obeyed pseudo zero-order kinetics at initial stage. The photodegradation rate constants of the three PAEs followed the order of DMP < DEP < DPP under most tested conditions. The pH dependency of photodegradation rate constants followed the order of DMP > DEP > DPP, with the rate constant of DMP photodegradation highly pH dependent and the rate constant of DPP pH independent. The photodegradation caused by photo-hydroxylation induced by hydroxyl radical and other non-hydroxyl radical induced processes was estimated using iso-propanol as hydroxyl radical scavenger. It was found that the relative importance of photo-hydrolysis and photo-hydroxylation processes decreased, and the importance of other processes, possibly the direct bond dissociation, increased from DMP, DEP, to DPP with the increase of alkyl side chain length. Under solar irradiation at the sea level, there was no observable degradation at pH 7.0, while slight degradation was observed at pH 2.0 for all the three PAEs studied.The effects of nitrite, nitrate, and Humic Acid (HA) on the photodegradation of DMP, DEP, and DPP were studied under UV and solar irradiation. Under UV irradiation, the presence of nitrite or nitrate promoted the photodegradation of all the three PAEs. In general, the promotion effect of nitrite is more significant than that of nitrate. The promotion effects were pH dependent and the dependency was more significant for nitrite than nitrate. Low concentration of HA can promote the photodegradation but HA in high concentration promoted the photodegradation of PAEs to less degrees or even inhibited the photodegradation. Under solar irradiation, the photodegradation was promoted by the presence of nitrite, nitrate, or HA. The photodegradation of PAEs could undergo four pathways: direct bond dissociation, photo-hydrolysis, photo-hydroxylation, and photo-nitration. In the absence of photosensitizers, with the increase of alkyl side chain length of PAEs, the proportion of phthalic acid monoesters (PMEs) in the intermediate products increased and that of the hydroxyl PAEs decreased. The formation of mono-methyl Phthalate (MMP) was pH dependent, and the formation of mono-ethyl Phthalate (MEP) and mono-propyl Phthalate (MPP) was almost pH independent. We proposed that the formation of PMEs was the combination of photo-hydrolysis and direct bond dissociation, with the formation of MMP mainly through photo-hydrolysis and the formation of MEP and MPP mainly through direct bond dissociation. In the photodegradation with photosensitizers, the decomposition of substrate is mainly caused by the photo-hydroxylation induced by hydroxyl radical, while direct photolysis plays a minor role. The formation of nitration products was favored in acidic conditions. The accumulation of nitration products was enhanced under solar irradiation. Nitration process should be considered in studying the behavior and fate of PAEs in the aquatic environment and in assessing their potential risk to public health and the ecosystem.

ISBN: 9798641709772Subjects--Topical Terms:

3168300
Analytical chemistry.
Subjects--Index Terms:

Humic acid

Effects of Nitrite, Nitrate, and Humic Acid on the Photodegradation of Dimethyl, Diethyl, and Dipropyl Phthalic Acid Ester.
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500 $a Source: Dissertations Abstracts International, Volume: 81-12, Section: B.
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502 $a Thesis (Ph.D.)--University of Massachusetts Lowell, 2020.
506 $a This item must not be sold to any third party vendors.
520 $a Phthalic Acid Esters (PAEs) have been intensively used in the manufacturing of plastics and other products. During the whole life cycle of these products, PAEs can be readily released into the environment and pose risks to public health and the ecosystem because of their reproductive and developmental toxicity, carcinogenicity, and chronic organ toxicity to human and wildlife. Knowledge on the occurrence, behavior, and fate of PAEs in the environment is essential for assessing the risk and making policies to control the PAEs. Photodegradation studies of PAEs were conducted in this study to elucidate the behavior and fate of PAEs in the environment.A LC-MS/MS method was developed at first to quantify and identify the PAEs and their photodegradation intermediate products. LC mobile phase conditions including type of organic solvent, organic solvent content, and flow rate were evaluated to find out the best combination for separation and quantitation purposes. Effects of Electrospray Ionization (ESI) parameters including capillary voltage, sampling cone voltage, extraction cone voltage, source temperature, desolvation temperature, cone gas flow rate, and desolvation gas flow rate on the ionization efficiency were systematically investigated and optimized using One-Variable-at-A-Time (OVAT) strategy. The optimized LC-MS/MS method was used to identify and quantify the photodegradation intermediate products of PAEs. The direct photodegradation of Dimethyl Phthalate (DMP), Diethyl Phthalate (DEP), and Dipropyl Phthalate (DPP) were conducted under UV and solar irradiation. Under UV irradiation, the photodegradation obeyed pseudo zero-order kinetics at initial stage. The photodegradation rate constants of the three PAEs followed the order of DMP < DEP < DPP under most tested conditions. The pH dependency of photodegradation rate constants followed the order of DMP > DEP > DPP, with the rate constant of DMP photodegradation highly pH dependent and the rate constant of DPP pH independent. The photodegradation caused by photo-hydroxylation induced by hydroxyl radical and other non-hydroxyl radical induced processes was estimated using iso-propanol as hydroxyl radical scavenger. It was found that the relative importance of photo-hydrolysis and photo-hydroxylation processes decreased, and the importance of other processes, possibly the direct bond dissociation, increased from DMP, DEP, to DPP with the increase of alkyl side chain length. Under solar irradiation at the sea level, there was no observable degradation at pH 7.0, while slight degradation was observed at pH 2.0 for all the three PAEs studied.The effects of nitrite, nitrate, and Humic Acid (HA) on the photodegradation of DMP, DEP, and DPP were studied under UV and solar irradiation. Under UV irradiation, the presence of nitrite or nitrate promoted the photodegradation of all the three PAEs. In general, the promotion effect of nitrite is more significant than that of nitrate. The promotion effects were pH dependent and the dependency was more significant for nitrite than nitrate. Low concentration of HA can promote the photodegradation but HA in high concentration promoted the photodegradation of PAEs to less degrees or even inhibited the photodegradation. Under solar irradiation, the photodegradation was promoted by the presence of nitrite, nitrate, or HA. The photodegradation of PAEs could undergo four pathways: direct bond dissociation, photo-hydrolysis, photo-hydroxylation, and photo-nitration. In the absence of photosensitizers, with the increase of alkyl side chain length of PAEs, the proportion of phthalic acid monoesters (PMEs) in the intermediate products increased and that of the hydroxyl PAEs decreased. The formation of mono-methyl Phthalate (MMP) was pH dependent, and the formation of mono-ethyl Phthalate (MEP) and mono-propyl Phthalate (MPP) was almost pH independent. We proposed that the formation of PMEs was the combination of photo-hydrolysis and direct bond dissociation, with the formation of MMP mainly through photo-hydrolysis and the formation of MEP and MPP mainly through direct bond dissociation. In the photodegradation with photosensitizers, the decomposition of substrate is mainly caused by the photo-hydroxylation induced by hydroxyl radical, while direct photolysis plays a minor role. The formation of nitration products was favored in acidic conditions. The accumulation of nitration products was enhanced under solar irradiation. Nitration process should be considered in studying the behavior and fate of PAEs in the aquatic environment and in assessing their potential risk to public health and the ecosystem.
590 $a School code: 0111.
650 4 $a Analytical chemistry. $3 3168300
650 4 $a Environmental science. $3 677245
653 $a Humic acid
653 $a LC-MS/MS
653 $a Nitrate
653 $a Nitrite
653 $a Photodegradation
653 $a Phthalic acid esters
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710 2 $a University of Massachusetts Lowell. $b Chemistry. $3 3547370
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791 $a Ph.D.
792 $a 2020
793 $a English
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