真空紫外光解二氯甲烷去除机理研究 - Journal of Environmental.DOC

Conversion characteristics and mechanism analysis of gaseous dichloromethane degraded by a VUV light in different reaction media Jianming Yu1, Wenji Cai 1, Jianmeng Chen1, *, Li Feng2, Yifeng Jiang1, Zhuowei Cheng2, * 1. College of Biological and Environmental Engineering, Zhejiang University of Technology, Hangzhou 310032, China. E-mail: yjm@zjut.edu.cn 2. Environmental Science and Engineering Research Institute, Zhejiang University of Technology, Hangzhou 310032, China. Received 31 December 2011; revised 25 April 2012; accepted 15 May 2012 Abstract: 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 HCl, CO2, H2O, 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 subsequent biodegradation. Key Words：ichloromethane; VUV photodegradation; mechanism; carbon balance; kinetic analysis DOI: 10.1016/S1001-0742(11)61021-8 ----------------------- * Corresponding a