Conversion characteristics and kinetic analysis of gaseous α-pinene degraded by a VUV light in various reaction media

The photodegradation of gaseous alpha-pinene by a vacuum ultraviolet (VUV) light was investigated under different process parameters and reaction media. The degradation of alpha-pinene was examined at nominal concentrations ranging from 50 to 1000 ppm, and resulted from the combination of direct photolysis, OH center dot oxidation and O-3 oxidation, in which O-3 oxidation played a dominant role. A high conversion efficiency of alpha-pinene was achieved at a moderate relative humidity (RH) of 35-40% with an efficient utilization of the electrical energy. The conversion of alpha-pinene were remarkably reduced while a RH was increased to 75-80% since a higher RH inhibited the production of ozone and further affected the conversion of alpha-pinene adversely. The alpha-pinene conversion followed the first-order kinetic model at the low initial concentrations (50-200 ppm), and the second-order kinetic model provided a good fit to the data at the high concentrations (400-1000ppm). The kinetic models including the initial target concentrations and the produced ozone amounts were developed to describe their mutual relationships. Preliminary results indicate that the VUV photooxidation was an appropriate technology for conversion of alpha-pinene not only as a single treatment but also as a pretreatment followed by the subsequent biodegradation. (C) 2010 Elsevier B.V. All rights reserved.