Comparison of Chlorine Dioxide and Ozone as Oxidants for the Degradation of Volatile Organic Compounds

Abstract

The presence of hazardous volatile organic compounds (VOCs) in both indoor and outdoor air is a grave issue in environmental pollution. The exposure of these compounds may cause chronic disease or adverse effects in humans. The major sources of these toxic compounds are due to improper waste disposal by chemical manufacturers, the waste stream from food processing, industrial sources, and decay of living cells. Therefore, the reduction of VOCs by oxidative reactions is the primary goal of this thesis project. Both chlorine dioxide and ozone are used to evaluate the degradation characteristics of dimethyl trisulfide, isoprene, 1-bromopropane, 2,3-butanedione, and 1,1,2-trichloroethane. Gas chromatography coupled to mass spectroscopy (GC-MS) and Fourier Transform infrared spectrometry (FTIR) were used to characterize the gas phase reaction products of these compounds. The results show that dimethyl trisulfide and isoprene were substantially degraded into other by-products, including methane sulfonyl chloride and sulfur dioxide, during oxidation by chlorine dioxide and ozone, respectively. In contrast, 1-bromopropane, 2,3-butanedione and 1,1,2-trichloroethane have slow reaction kinetics and did not break down completely. Degradation of dimethyl trisulfide by chlorine dioxide and ozone follows the second-order kinetics with half-lives of 2.2 min and 24 min, respectively. On the other hand, isoprene follows the first order reaction kinetics with rate constants of 0.4051 min-1 and 0.02244 min-1 and half-lives of 1.73 min and 32 min for degradation using ozone and chlorine dioxide, respectively. The oxidative degradation of 1-bromopropane, dimethyl trisulfide, and 2,3-butanedione by chlorine dioxide was more efficient than their reactions with ozone. However, the degradation of isoprene and 1,1,2-trichloroethane showed a greater reactivity toward ozone compared to chlorine dioxide. Most of the reaction products of oxidative degradation such as acetone, ethanol, formic acid, and dimethyl ether are chemically benign. But there are also by-products such as methane sulfonyl chloride, sulfur dioxide, chloroform, and cyanogen bromide that require further toxicological study.