大气液相中对氯甲苯与超氧阴离子自由基光化学反应

文章利用 365 nm 紫外光辐照核黄素(Rf)与对氯甲苯(PCT)混合溶液, 探讨对氯甲苯与超氧阴离子自由基( $ O_{2}^{-}\cdot $)在大气液相中的光化学反应。考察 PCT 和核黄素初始浓度、溶液初始 pH 值及液滴尺寸等因素对光致反应的影响, 并对光致转化产物进行气相色谱-质谱 (gas chromatography-mass spectrometry, GC-MS) 分析。分析结果表明: Rf 经 365 nm 紫外光激发可产生 $ O_{2}^{-}\cdot $, PCT 与 $ O_{2}^{-}\cdot $ 的二级反应速率常数为 $ 2.66\ \mathrm{L}/(\mathrm{mol}\cdot\mathrm{s}) $; PCT 的转化速率随 Rf 浓度的增加先增加后降低, 而随初始 pH 值的增加而降低; 液滴尺寸对 PCT 的转化速率有较大影响, 光照 5 min 时 PCT 液滴直径为 2~3 mm 的转化速率是其溶液的 6.3 倍。

In this paper, the photochemical reaction of p-chlorotoluene(PCT) with superoxide anion radical( $ O_{2}^{-}\cdot $) in atmospheric aqueous phase was investigated by irradiating a mixture of riboflavin (Rf) and PCT with 365 nm ultraviolet light. The influences of PCT and Rf initial concentration, initial pH value of the solution and droplet size on the photoinduced reaction were investigated, and the photoinduced conversion products were analyzed using gas chromatography-mass spectrometry (GC-MS). The results show that $ O_{2}^{-}\cdot $ can be generated by Rf under 365 nm ultraviolet light excitation, and the second-order reaction rate constant of PCT with $ O_{2}^{-}\cdot $ is $ 2.66\ \mathrm{L}/(\mathrm{mol}\cdot\mathrm{s}) $. The conversion rate of PCT first increases and then decreases with the increase of Rf concentration, and decreases with the increase of initial pH value. The droplet size has a great influence on the conversion rate of PCT. The conversion rate of PCT when the droplet diameter is 2-3 mm is 6.3 times that of the solution under 5 min illumination.