Evaluate UV-LEDs for UV/Chlorine Advanced Oxidation

紫外发光二极管（UV LEDs）正迅速成为一种有吸引力的水处理工具，用于消毒微生物和去除微污染物。与目前水处理厂采用的传统汞灯不同，它们结构紧凑，不含汞，并且可以立即打开和关闭。因此，它们有可能取代传统的紫外线灯。led在水处理中的一个更新颖的应用是高级氧化工艺（AOPs）。在以紫外线为基础的AOPs中，紫外线被用来将化学物质分解成活性的“自由基”物种，这些物质可以迅速破坏水中的污染物。迄今为止，大多数基于紫外线的AOPs使用汞灯来产生紫外线。然而，在不同的已知AOPs中，使用紫外光子将氯分解成自由基的UV/Cl2可能特别适合使用led作为光源。这是因为氯在紫外发光二极管比传统汞灯更有效地发光的波长上显示出很高的紫外线吸收率。不幸的是，没有关于UV led相对于汞灯在UV/Cl2去除微污染物方面的性能的信息，也没有关于可能产生的副产品以及它们是否有毒的信息。例如，氯酸盐，已知是由使用传统紫外线灯的UV/Cl2过程中产生的自由基形成的，安大略省政府目前将饮用水中的氯酸盐控制在每升1毫克，因为它具有毒性。据推测，当使用led时，由于其低强度和低能量的紫外线输出，导致氯酸盐的特定自由基可能不太占优势。这将是第一个通过量化led相对于低压和中压汞灯的竞争力来评估UV/Cl2 AOP的研究，该研究基于(1)对微污染物的控制和(2)氯酸盐和其他相关副产品的生产。

Ultraviolet light-emitting diodes (UV LEDs) are fast becoming an attractive water treatment tool to disinfect the microorganisms and to remove the micropollutants. Different from the conventional mercury lamps which are currently adopted by the water treatment plants, they are compact, mercury-free, and can be turned on and off instantly. As such, they have the potential to replace conventional UV lamps. One of the more novel applications for LEDs in water treatment is in advanced oxidation processes (AOPs). In UV-based AOPs, UV light is used to split chemicals into reactive 'radical' species that can quickly destroy pollutants in water. To-date, most UV-based AOPs employ mercury lamps to generate the UV light. However, among the different known AOPs, UV/Cl2, which uses UV photons to split chlorine into radicals, may be particularly well-suited to using LEDs as the light source. This is because chlorine shows a high UV absorptivity at the wavelengths where UV LEDs can produce light more efficiently than conventional mercury lamps. Unfortunately, there is no information on the performance of UV LEDs relative to mercury lamps in the context of micropollutant removal by UV/Cl2, nor is there information on the byproducts that may be generated and whether or not they may be toxic. For example, chlorate, is known to form from radicals produced during UV/Cl2 processes that employ conventional UV lamps, and the government of Ontario currently regulates chlorate at 1 mg/L in drinking water due to its toxicity. It is hypothesized that the specific radicals leading to chlorate may be less predominant when using LEDs due to their low intensity and low energy UV output. This will be the first study evaluating the UV/Cl2 AOP by quantifying the competitiveness of LEDs relative to low and medium pressure mercury lamps on the basis of (1) the control of micropollutants and (2) the production of chlorate and other relevant byproducts.