TY - JOUR
T1 - Mechanism of nitrite formation by nitrate photolysis in aqueous solutions
T2 - The role of peroxynitrite, nitrogen dioxide, and hydroxyl radical
AU - Goldstein, Sara
AU - Rabani, Joseph
PY - 2007/8/29
Y1 - 2007/8/29
N2 - Photolysis of aqueous NO3- with λ ≥ 195 nm is known to induce the formation of NO2- and O2 as the only stable products. The mechanism of NO3- photolysis, however, is complex, and there is still uncertainty about the primary photoprocesses and subsequent reactions. This is, in part, due to photoisomerization of NO3- to ONOO- at λ < 280 nm, followed by the formation of •OH and •NO2 through the decomposition of ONOOH (pKa = 6.5-6.8). Because of incomplete information concerning the mechanism of peroxynitrite (ONOOH/ONOO-) decomposition, previous studies were unable to account for all observations. In the present study aqueous nitrate solutions were photolyzed by monochromatic light in the range of 205-300 nm. It is shown that the main primary processes at this wavelength range are NO3 - → hv •NO2 + O •- (reaction 1) and NO3- → hv ONOO- (reaction 2). Based on recent knowledge on the mechanisms of peroxynitrite decomposition and its reactions with reactive nitrogen and oxygen species, we determined Φ(1) and Φ(2) using different experimental approaches. Both quantum yields increase with decreasing the excitation wavelength, approaching Φ(1) = 0.13 and Φ(2) = 0.28 at 205 nm. It is also shown that the yield of nitrite increases with decreasing the excitation wavelength. The implications of these results on UV disinfection of drinking water are discussed.
AB - Photolysis of aqueous NO3- with λ ≥ 195 nm is known to induce the formation of NO2- and O2 as the only stable products. The mechanism of NO3- photolysis, however, is complex, and there is still uncertainty about the primary photoprocesses and subsequent reactions. This is, in part, due to photoisomerization of NO3- to ONOO- at λ < 280 nm, followed by the formation of •OH and •NO2 through the decomposition of ONOOH (pKa = 6.5-6.8). Because of incomplete information concerning the mechanism of peroxynitrite (ONOOH/ONOO-) decomposition, previous studies were unable to account for all observations. In the present study aqueous nitrate solutions were photolyzed by monochromatic light in the range of 205-300 nm. It is shown that the main primary processes at this wavelength range are NO3 - → hv •NO2 + O •- (reaction 1) and NO3- → hv ONOO- (reaction 2). Based on recent knowledge on the mechanisms of peroxynitrite decomposition and its reactions with reactive nitrogen and oxygen species, we determined Φ(1) and Φ(2) using different experimental approaches. Both quantum yields increase with decreasing the excitation wavelength, approaching Φ(1) = 0.13 and Φ(2) = 0.28 at 205 nm. It is also shown that the yield of nitrite increases with decreasing the excitation wavelength. The implications of these results on UV disinfection of drinking water are discussed.
UR - http://www.scopus.com/inward/record.url?scp=34548211407&partnerID=8YFLogxK
U2 - 10.1021/ja073609+
DO - 10.1021/ja073609+
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AN - SCOPUS:34548211407
SN - 0002-7863
VL - 129
SP - 10597
EP - 10601
JO - Journal of the American Chemical Society
JF - Journal of the American Chemical Society
IS - 34
ER -