Civil and Urban Engineering Department, Tandon School of Engineering, New York University, Brooklyn, New York 11201, USA.
Environ Sci Process Impacts. 2024 Jun 19;26(6):1052-1063. doi: 10.1039/d4em00084f.
Accurate quantum yields are crucial for modeling photochemical reactions in natural and engineered treatment systems. Quantum yields are usually determined using a single representative light source such as xenon lamps to mimic sunlight or UVC light for water treatment. However, photodegradation modeling can be improved by understanding the wavelength dependence of quantum yields and the potential errors introduced by the experimental setup. In this study, we investigated the effects of experimental setup on measured quantum yields using four photoreactor systems and up to 11 different light sources. When using a calibrated spectroradiometer to measure incident irradiance on an open solution surface, apparent quantum yields were up to two times higher if light reflection and light screening were not accounted for in the experimental setup. When the experimental setup was optimized to allow for accurate irradiance measurements, quantum yields were reproducible across photoreactors. The optimized experimental setup was then used to determine quantum yields of uridine, atrazine, -nitroanisole (PNA), sulfamethoxazole, and diclofenac across the UV spectrum. No significant wavelength dependence of quantum yields was observed for sulfamethoxazole and diclofenac, in contrast to wavelength-dependent quantum yields for uridine, atrazine, and PNA. These reference values can be used for determining wavelength-dependent quantum yields of other compounds of interest. Additionally, more accurate results can be obtained when using (1) an actinometer with similar light absorption and photoreactivity compared to that of the target chemical, (2) optically transparent actinometer solutions that can account for light reflection within reaction vessels, and (3) a quantum yield that corresponds to the spectrum of the selected light source.
准确的量子产率对于模拟自然和工程处理系统中的光化学反应至关重要。量子产率通常使用单一代表性光源（如氙灯）来确定，以模拟阳光或 UVC 光用于水处理。然而，通过了解量子产率的波长依赖性以及实验设置引入的潜在误差，可以改进光降解建模。在这项研究中，我们使用四个光反应器系统和多达 11 种不同的光源，研究了实验设置对测量量子产率的影响。当使用校准的分光辐射计测量开放溶液表面的入射辐照度时，如果实验设置中没有考虑光反射和光屏蔽，则表观量子产率最高可提高两倍。当实验设置得到优化以允许进行准确的辐照度测量时，量子产率在光反应器之间具有重现性。然后，使用优化的实验设置来确定尿嘧啶、莠去津、-硝基苯甲醚 (PNA)、磺胺甲恶唑和双氯芬酸在整个 UV 光谱范围内的量子产率。与尿嘧啶、莠去津和 PNA 的波长依赖性量子产率相反，磺胺甲恶唑和双氯芬酸的量子产率没有明显的波长依赖性。这些参考值可用于确定其他感兴趣化合物的波长依赖性量子产率。此外，当使用 (1) 与目标化学物质具有相似光吸收和光反应性的光化剂，(2) 能够考虑反应容器内光反射的光学透明光化剂溶液，以及 (3) 与所选光源光谱相对应的量子产率时，可以获得更准确的结果。
