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Aromatic photonitration in homogeneous and heterogeneous aqueous systems
Davide Vione1, Valter Maurino, Claudio Minero
1Dipartimento di Chimica Analitica, Università di Torino, Via P. Giuria 5, I-10125 Torino, Italy.
Environmental Science and Pollution Research International
|October 11, 2003
Summary
This study shows that near-UV light can nitrate aromatic compounds in water. Photocatalysis using TiO2 enhances this process, revealing new roles for nitrite in natural environments.
Area of Science:
- Environmental Chemistry
- Photochemistry
- Catalysis
Background:
- Aromatic compounds are widespread in natural waters and the atmosphere.
- Nitrite is a common species in aquatic and atmospheric systems.
- Understanding nitration pathways is crucial for environmental chemistry.
Purpose of the Study:
- To investigate the photoinduced nitration of aromatic compounds in aqueous solutions.
- To explore the role of nitrite and nitrate photolysis in this process.
- To evaluate the enhancement effect of titanium dioxide (TiO2) photocatalysis.
Main Methods:
- Near-UV photolysis of nitrate and nitrite in aqueous solution.
- Photocatalytic oxidation of nitrite using TiO2 suspensions.
- Using phenol as a model aromatic compound and probe for nitrogen dioxide (*NO2/N2O4).
Main Results:
- Photoinduced nitration of phenol was observed via reaction with *NO2 or N2O4.
- The nitration process was enhanced by the photocatalytic oxidation of nitrite to *NO2 by TiO2.
- Aromatic photonitration in the liquid phase was identified as a significant pathway for nitroaromatic formation.
Conclusions:
- Liquid-phase aromatic photonitration is a relevant pathway for nitroaromatic formation in natural waters and atmospheric hydrometeors.
- Photocatalytic oxidation of nitrite by TiO2 enhances aromatic nitration.
- This study suggests a novel role for nitrite in natural waters and atmospheric aerosols through photoinduced oxidation to nitrogen dioxide.