Conversion characteristics and mechanism analysis of gaseous dichloromethane degraded by a VUV light in different reaction media  

作　　者：Jianming Yu Wenji Cai Jianmeng Chen Li Feng Yifeng Jiang Zhuowei Cheng 

机构地区：[1].College of Biological and Environmental Engineering, Zhefiang University of Technology, Hangzhou 310032, China [2]Environmental Science and Engineering Research Institute, Zhefiang University of Technology, Hangzhou 310032, China

出　　处：《Journal of Environmental Sciences》2012年第10期1777-1784,共8页环境科学学报（英文版）

基　　金：supported by the National Natural Science Foundation of China (No. 20976165,21207115);the Ph.D.Programs Foundation of Ministry of Education of China(No. 20093317110003);the Zhejiang Provincial Funds for Distinguished Young Scientists (No. R5090230)

摘　　要：The photodegradation of gaseous dichloromethane （DCM） by a vacuum ultraviolet （VUV） light in a spiral reactor was investigated with different reaction media and initial concentrations. Through the combination of direct photolysis, O3 oxidation and HO. oxidation, DCM was ultimately mineralized into inorganic compounds （such as HC1, CO2, H20, etc.） in the air with relative humidity （RH） of 75%-85%. During the photodegradation process, some small organic acids （including formic acid, acetic acid） were also detected and the intermediates were more soluble than DCM, providing a possibility for its combination with subsequent biodegradation. Based on the detected intermediates and the confirmed radicals, a photodegradation pathway of DCM by VUV was proposed. With RH 75%- 80% air as the reaction medium, the DCM removal followed the second-order kinetic model at inlet concentration of 100-1000 mg/m3. Kinetic analysis showed that the reaction media affected the kinetic constants of DCM conversion by a large extent, and RH 80% air could cause a much lower half-life for its conversion. Such results supported the possibility that VUV photodegradation could be used not only for the mineralization of DCM but also as a pretreatment before biodegradation.The photodegradation of gaseous dichloromethane （DCM） by a vacuum ultraviolet （VUV） light in a spiral reactor was investigated with different reaction media and initial concentrations. Through the combination of direct photolysis, O3 oxidation and HO. oxidation, DCM was ultimately mineralized into inorganic compounds （such as HC1, CO2, H20, etc.） in the air with relative humidity （RH） of 75%-85%. During the photodegradation process, some small organic acids （including formic acid, acetic acid） were also detected and the intermediates were more soluble than DCM, providing a possibility for its combination with subsequent biodegradation. Based on the detected intermediates and the confirmed radicals, a photodegradation pathway of DCM by VUV was proposed. With RH 75%- 80% air as the reaction medium, the DCM removal followed the second-order kinetic model at inlet concentration of 100-1000 mg/m3. Kinetic analysis showed that the reaction media affected the kinetic constants of DCM conversion by a large extent, and RH 80% air could cause a much lower half-life for its conversion. Such results supported the possibility that VUV photodegradation could be used not only for the mineralization of DCM but also as a pretreatment before biodegradation.

关 键 词：DICHLOROMETHANE VUV photodegradation MECHANISM carbon balance kinetic analysis 

分 类 号：X788[环境科学与工程—环境工程] O753.2[理学—晶体学]