太阳光下水中2,4,6-三氯酚的光解机制研究

Studies on the photodecomposition mechanism of 2,4,6-trichlorophenol in water under sunlight irradiation

对比研究了太阳光下2,4,6-三氯酚(2,4,6-TCP)在纯水,可溶性有机质(DOM)溶液和实际地表水中的光解情况.结果表明,2,4,6-TCP在纯水中主要为直接光解和自敏化光解,涉及的活性物种为单线态氧;在DOM水溶液中主要为直接光解和敏化光解,涉及的活性物种为单线态氧和羟基自由基;2,4,6-TCP在纯水,DOM溶液和实际地表水中的光解速率均随溶液含氧量的提高而增加.太阳光可见区对2,4,6-TCP直接光解没有贡献,UVA贡献为72.60%,而当有DOM存在时,可见光区对2,4,6-TCP的光解贡献为12.39%,UVA的贡献为52.73%.2,4,6-TCP在实际地表水中的光解与在DOM水溶液中的光解类似,都表现为通氮抑制光解,通氧促进光解,并且光谱贡献率也十分接近,表明溶解氧和DOM是2,4,6-TCP在地表水中间接光解的主要影响因素.

The photodecompositions of 2,4,6-trichlorophenol （2,4,6-TCP） in pure water, dissolved organic matter （DOM） solution, and actual surface water were studied comparatively. The results indicate that there are three pathways in the photodecomposition of 2,4,6-TCP, including direct photolysis, sensitized photolysis, and self-sensitized photolysis. Direct photolysis and self-sensitized are found to be involved in the photolysis of 2,4,6-trichlorophenol in pure water, with singlet oxygen as main active species. Besides direct photolysis, sensitized photolysis of 2,4,6-trichlorophenol is also found in presence of DOM with singlet oxygen and hydroxyl radical as main active species. The degradation rates of 2,4,6-trichlorophenol in pure, DOM-contained and actual surface water all increase with the oxygen content in solution. The visible light has no contribution for the direct photolysis of 2,4,6-TCP, and UVA contribution is 72.60%. While in presence of dissolved organic matter, about 12.39% contribution of visible light is found, and the contribution of UVA is 52.73% in DOM solution. The photolysis of 2,4,6-trichlorophenol in actual surface water is similar to that in DOM solution, in which DO and DOM are the dominant factors in the indirect photolysis of 2,4,6-TCP.