Goldstein Sara, Rabani Joseph
Institute of Chemistry and The Accelerator Laboratory, The Hebrew University of Jerusalem, Jerusalem 91904, Israel.
Environ Sci Technol. 2008 May 1;42(9):3248-53. doi: 10.1021/es702563b.
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 NO3- containing RH (RH = HCO2-, CH3OH, or C2H5OH) and H2O2 containing CH3OH, all in aerated buffered aqueous solutions. The UV photolysis of NO3- generates ONOO-, *OH, and *NO2 intermediates and the stable NO2- 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 NO2- 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.
紫外线（UV）是一种经证实的用于饮用水消毒和净化的技术。为此，低压单色汞弧灯和中压多色汞弧灯都被广泛使用。单色光光子辐照度的测量方法不一定适用于多色光，特别是在涉及大量水的情况下，对多色光测量方法的需求尤为迫切。本论文报道了在曝气缓冲水溶液中，对含RH（RH = HCO2-、CH3OH或C2H5OH）的硝酸盐水溶液和含CH3OH的过氧化氢进行多色紫外光解的对比研究。硝酸根离子的紫外光解会产生过氧亚硝酸根离子、羟基自由基和二氧化氮自由基中间体以及稳定的亚硝酸根离子。在RH存在的情况下可获得最高产率的亚硝酸根离子。过氧化氢的紫外光解会产生羟基自由基，在甲醇存在时会生成甲醛。过氧化氢/甲醇光化学 actinometer 仅限于低光强和中等光强，因为反应机制涉及二级和一级过程之间的竞争。因此，尽管亚硝酸根离子的量子产率相对较低且其依赖于激发波长，但在高光子辐照度下，硝酸根离子 actinometer 更可取。将这两种 actinometer 与辐射测量法以及碘化物/碘酸盐 actinometer 进行了比较。由于光产物I3-的吸收，后者仅限于200 - 280 nm范围。硝酸根离子/C2H5OH actinometer 对于工业高强度紫外光反应器中的大量水特别有用，因为 actinometer 溶液可以安全处置。
