title: Conversion characteristics and mechanism analysis of gaseous dichloromethane degraded by a VUV light in different reaction media.
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 biodegradation.
authors.affiliation: College of Biological and Environmental Engineering, Zhejiang University of Technology, Hangzhou 310032, China. yjm@zjut.edu.cn
authors.forename: Jianming
authors.initials: J
authors.lastname: Yu
authors.forename: Wenji
authors.initials: W
authors.lastname: Cai
authors.forename: Jianmeng
authors.initials: J
authors.lastname: Chen
authors.forename: Li
authors.initials: L
authors.lastname: Feng
authors.forename: Yifeng
authors.initials: Y
authors.lastname: Jiang
authors.forename: Zhuowei
authors.initials: Z
authors.lastname: Cheng
mesh_terms: D000393:Air Pollutants / Q000737:chemistry*; D052918:Environmental Restoration and Remediation / Q000379:methods*; D007700:Kinetics; D008752:Methylene Chloride / Q000737:chemistry*; D009584:Nitrogen / Q000737:chemistry; D055668:Photochemical Processes; D014466:Ultraviolet Rays; D014618:Vacuum
chemical_list: D000393:Air Pollutants; D008752:Methylene Chloride; D009584:Nitrogen