Li Chenguang, Zhang Yanlei, Yin Shiqi, Wang Qin, Li Yuanyuan, Liu Qiang, Liu Liuqingqing, Luo Xianxiang, Chen Lingyun, Zheng Hao, Li Fengmin
Institute of Coastal Environmental Pollution Control, Ministry of Education Key Laboratory of Marine Environment and Ecology, College of Environmental Science and Engineering, Sanya Oceanographic Institute, Ocean University of China, Qingdao 266100, China.
Institute of Coastal Environmental Pollution Control, Ministry of Education Key Laboratory of Marine Environment and Ecology, College of Environmental Science and Engineering, Sanya Oceanographic Institute, Ocean University of China, Qingdao 266100, China; Marine Ecology and Environmental Science Laboratory, Pilot National Laboratory for Marine Science and Technology, Qingdao 266071, China.
J Hazard Mater. 2023 Oct 5;459:132127. doi: 10.1016/j.jhazmat.2023.132127. Epub 2023 Jul 23.
p-Phenylenediamines (PPDs), an important type of rubber antioxidants, have received little study on their environmental fate, particularly for their vital photodegradation process in water environment. Accordingly, N-(1,3-dimethylbutyl)-N'-phenyl-1,4-phenylenediamine (6PPD), as a representative of PPDs, was investigated experimentally and theoretically for its photodegradation in water. Rapid photodegradation occurred when 6PPD was exposed to illumination especially UV region irradiation. Under acidic conditions, the photodegradation of 6PPD accelerated mainly due to the increased absorption of long wavelength irradiation by ionized 6PPD. Nine photodegradation products (e.g., 6PPD-quinone (6PPDQ)) of 6PPD were identified by an ultra-performance liquid chromatography QTOF mass spectrometry. Molar yields of photoproducts such as 6PPDQ, aniline, 4-aminodiphenylamine, and 4-hydroxydiphenylamine were 0.03 ± 0.00, 0.10 ± 0.01, 0.03 ± 0.02, and 0.08 ± 0.01, respectively. Mechanisms involved in 6PPD photodegradation include photoexcitation, direct photolysis, self-sensitized photodegradation, and O oxidation, as demonstrated by electron paramagnetic resonance (EPR) analysis, scavenging experiments, and the time-dependent density functional theory (TD-DFT). Notably, the toxicity of the reaction solution formed during the photodegradation of 6PPD was increased by the formation of highly toxic products (e.g., 6PPDQ). This study provides the first explanation for photodegradation mechanisms of 6PPD and confirms the pathway of 6PPDQ produced by the photoreaction in water environment.
对苯二胺（PPDs）是一类重要的橡胶抗氧化剂，但其环境归宿方面的研究较少，尤其是在水环境中的关键光降解过程。因此，以N-（1,3-二甲基丁基）-N'-苯基对苯二胺（6PPD）作为PPDs的代表，对其在水中的光降解进行了实验和理论研究。当6PPD暴露于光照尤其是紫外区域照射时，会发生快速光降解。在酸性条件下，6PPD的光降解加速，主要是由于离子化的6PPD对长波长辐射的吸收增加。通过超高效液相色谱QTOF质谱鉴定出了6PPD的9种光降解产物（如6PPD-醌（6PPDQ））。6PPDQ、苯胺、4-氨基二苯胺和4-羟基二苯胺等光产物的摩尔产率分别为0.03±0.00、0.10±0.01、0.03±0.02和0.08±0.01。电子顺磁共振（EPR）分析、清除实验和含时密度泛函理论（TD-DFT）表明，6PPD光降解涉及的机制包括光激发、直接光解、自敏化光降解和O氧化。值得注意的是，6PPD光降解过程中形成的反应溶液的毒性因高毒性产物（如6PPDQ）的形成而增加。本研究首次解释了6PPD的光降解机制，并证实了水环境中光反应产生6PPDQ的途径。
