Photosensitized degradation of caffeine: Role of fulvic acids and nitrate

► Caffeine photodegradation occurs slowly in water. ► Caffeine photodegradation is enhanced in the presence of fulvic acids. ► Caffeine indirect photolysis at 10 μM and higher reacts via the hydroxyl radical. ► Nitrate enhances caffeine’s hydroxyl radical pathway. ► Photolysis at low initial concent...

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Vydáno v:Chemosphere (Oxford) Ročník 86; číslo 2; s. 124 - 129
Hlavní autoři: Jacobs, Laura E., Weavers, Linda K., Houtz, Erika F., Chin, Yu-Ping
Médium: Journal Article
Jazyk:angličtina
Vydáno: Kidlington Elsevier Ltd 2012
Elsevier
Témata:
Applied sciences
Benzopyrans
Benzopyrans - chemistry
Caffeine
Caffeine - chemistry
chemistry
Degradation
Dissolved organic matter
effluents
Environmental Restoration and Remediation
Exact sciences and technology
Fulvic acid
fulvic acids
Hydrogen-Ion Concentration
Hydroxyl Radical
Hydroxyl Radical - chemistry
hydroxyl radicals
iron
Irradiation
isopropyl alcohol
Nitrates
Nitrates - chemistry
oxygen
Pathways
Photolysis
Pollution
Radicals
rivers
solar radiation
streams
Sunlight
Waste Disposal, Fluid
Waste water
Wastewater
women
Ohio
Georgia
United States
North America
America
USA, Erie L., Old Woman Creek
USA, Florida, Suwannee R
Dissolved organic matter
Fulvic acid
Photolysis
Wastewater
Caffeine
Organic matter
Pollutant behavior
Nitrogen compounds
Environmental factor
Nitrates
Alkaloid
Selfpurification
Surface water
Water pollution
Waste water discharge
Photosensitizer
Organic compounds
Photochemical degradation
ISSN:0045-6535, 1879-1298, 1879-1298
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Shrnutí:► Caffeine photodegradation occurs slowly in water. ► Caffeine photodegradation is enhanced in the presence of fulvic acids. ► Caffeine indirect photolysis at 10 μM and higher reacts via the hydroxyl radical. ► Nitrate enhances caffeine’s hydroxyl radical pathway. ► Photolysis at low initial concentration caffeine ( <0.1 μM) occurs more quickly. The photolysis of caffeine was studied in solutions of fulvic acid isolated from Suwannee River, GA (SRFA) and Old Woman Creek Natural Estuarine Research Reserve, OH (OWCFA) with different chemical amendments (nitrate and iron). Caffeine degrades slowly by direct photolysis (>170 h in artificial sunlight), but we observed enhanced photodegradation in waters containing the fulvic acids. At higher initial concentrations (10 μM) the indirect photolysis of caffeine occurs predominantly through reaction with the hydroxyl radical (OH ) generated by irradiated fulvic acids. Both rate constant estimates based upon measured OH steady-state concentrations and quenching studies using isopropanol corroborate the importance of this pathway. Further, OH generated by irradiated nitrate at concentrations present in wastewater effluent plays an important role as a photosensitizer even in the presence of fulvic acids, while the photo-Fenton pathway does not at neutral or higher pH. At lower initial concentrations (0.1 μM) caffeine photolysis reactions proceed even more quickly in fulvic acid solutions and are influenced by both short- and long-lived reactive species. Studies conducted under suboxic conditions suggest that an oxygen dependent long-lived radical e.g., peroxyl radicals plays an important role in the degradation of caffeine at lower initial concentration.
Bibliografie:ObjectType-Article-1
SourceType-Scholarly Journals-1
ObjectType-Feature-2
content type line 23
ISSN:0045-6535
1879-1298
1879-1298
DOI:10.1016/j.chemosphere.2011.09.052