TY - JOUR
T1 - Polychromatic UV photon irradiance measurements using chemical actinometers based on NO3- and H2O2 Excitation
T2 - Applications for industrial photoreactors
AU - Goldstein, Sara
AU - Rabani, Joseph
PY - 2008/5/1
Y1 - 2008/5/1
N2 - Ultraviolet light (UV) is a proven technology for disinfecting and decontaminating drinking water. For this purpose, both low-pressure monochromatic and medium-pressure polychromatic mercury arc lamps are commonly being used. Methods for photon irradiance measurements of monochromatic light are not necessarily appropriate for polychromatic light, and there is a need for the latter especially when large volumes of water are involved. The present manuscript reports a comparative study of polychromatic UV photolysis of aqueous N03- containing RH (RH = HC02-, CH3OH, or C2H5OH) and H20 2 containing CH3OH, all in aerated buffered aqueous solutions. The UV photolysis of NO3- generates ONOO - OH, and NO2 intermediates and the stable NO 2- ion. The maximum yield of NO2- is obtained in the presence of RH. The UV photolysis of H2O2 generates OH radicals, which in the presence of CH3OH form formaldehyde. The H2O2/CH3OH actinometer is limited to low and moderate light intensities because the reaction mechanism involves competition between second-and first-order processes. Therefore, the NO3- actinometer is preferable at high photon irradiance despite the relatively low quantum yield of N02- and its dependence on the excitation wavelength. The two actinometers are compared to radiometry and to iodide/iodate actinometer. The latter is limited to the 200-280 nm range due to the absorption of the photoproduct I3 -. The NO3-/C2H5OH actinometer is particularly useful for large volumes of water in industrial high-intensity UV photoreactors as the actinometer solution can be safely disposed.
AB - Ultraviolet light (UV) is a proven technology for disinfecting and decontaminating drinking water. For this purpose, both low-pressure monochromatic and medium-pressure polychromatic mercury arc lamps are commonly being used. Methods for photon irradiance measurements of monochromatic light are not necessarily appropriate for polychromatic light, and there is a need for the latter especially when large volumes of water are involved. The present manuscript reports a comparative study of polychromatic UV photolysis of aqueous N03- containing RH (RH = HC02-, CH3OH, or C2H5OH) and H20 2 containing CH3OH, all in aerated buffered aqueous solutions. The UV photolysis of NO3- generates ONOO - OH, and NO2 intermediates and the stable NO 2- ion. The maximum yield of NO2- is obtained in the presence of RH. The UV photolysis of H2O2 generates OH radicals, which in the presence of CH3OH form formaldehyde. The H2O2/CH3OH actinometer is limited to low and moderate light intensities because the reaction mechanism involves competition between second-and first-order processes. Therefore, the NO3- actinometer is preferable at high photon irradiance despite the relatively low quantum yield of N02- and its dependence on the excitation wavelength. The two actinometers are compared to radiometry and to iodide/iodate actinometer. The latter is limited to the 200-280 nm range due to the absorption of the photoproduct I3 -. The NO3-/C2H5OH actinometer is particularly useful for large volumes of water in industrial high-intensity UV photoreactors as the actinometer solution can be safely disposed.
UR - http://www.scopus.com/inward/record.url?scp=52049100628&partnerID=8YFLogxK
U2 - 10.1021/es702563b
DO - 10.1021/es702563b
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C2 - 18522101
AN - SCOPUS:52049100628
SN - 0013-936X
VL - 42
SP - 3248
EP - 3253
JO - Environmental Science and Technology
JF - Environmental Science and Technology
IS - 9
ER -