Environmental Engineering Reference
In-Depth Information
pH 4
pH 5
0.18
0.18
pH 6
pH 7
pH 8
pH 8
pH 9
pH 10
pH 11
0.14
0.14
0.1
0.1
0.06
0.06
0.02
0.02
278
298
318
353
278 288 298 308 318 328 338 348 358
Temperature (K)
•
of NO
2
-
photolysis with variation in temperature at a specific
wavelength at 308 nm for various pH (
a
) and at 351 nm (
b
) at pH 8.
Data source
Zellner et al.
(
1990
)
Fig. 4
Quantum yields of HO
These results allow the hypothesis that the temperature dependence of
Φ
HO
for
NO
2
-
photolysis is independent of wavelength, despite a decline of the absolute
Φ
HO
value with increasing wavelength (Fig.
4
) (Zellner et al.
1990
).
On the other hand, the
Φ
HO
of NO
3
-
photolysis has been determined for
a NO
3
-
concentration of 3
×
10
-3
M in the range 4
≤
pH
≤
11, at temperature
between 278-353 K and 308 nm irradiation (Table
5
) (Zellner et al.
1990
). The
absorption coefficient of NO
3
-
at 308 nm is
ε
308
=
6.5 L mol
-1
cm
-1
(Meyerstein
and Treinin
1961
). It has been shown that the quantum yields at each temperature
are generally independent of pH in the range 4
≤
pH
≤
9. At higher pH's, the
quantum yield is typically decreased (Fig.
5
).
Fig. 5
Quantum yields of
HO
pH 4
pH 5
0.044
•
of NO
3
-
photolysis with
variation in temperature at a
specific wavelength (308 nm)
for various pH.
Data source
Zellner et al. (
1990
)
pH 6
pH 7
pH 8
pH 9
pH 10
pH 11
0.033
0.022
0.011
0
278
298
318
353
Temperature (K)
