Treatment of Carcinogenic Volatile Organic Contaminants Using Uv and Uv/hydrogen Peroxide Advanced Oxidation Process

Mandona, Choolwe Milimo

Graduate Thesis Or Dissertation

Treatment of Carcinogenic Volatile Organic Contaminants Using Uv and Uv/hydrogen Peroxide Advanced Oxidation Process Public Deposited

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Citeable URL: https://scholar.colorado.edu/concern/graduate_thesis_or_dissertations/z316q203z

Abstract

Volatile organic compounds (VOCs) are chemicals that are potentially hazardous to human health and the environment. Some VOCs have been shown to cause cancer in animals and are classified as potential human carcinogens. The United States Environmental Protection Agency (USEPA) is considering regulating as many as 16 VOCs as a group instead of individually. This approach of regulating chemicals implies that these grouped chemicals could be remediated by a single technology or perhaps a group of technologies. Advanced oxidation processes (AOPs) such as ultra-violet (UV) light in combination with hydrogen peroxide (UV/H₂O₂) are potential treatment processes for VOC removal. Given the applicability of AOP as a VOC treatment technology, there are fundamental gaps to understand and predict the transformation of VOCs. There is a need to understand the removal efficiencies of individual VOCs with AOP and how the treatment process is affected by changes in the water matrix. Eleven VOCs were studied for their reactivity with UV and OH radicals using a low pressure mercury vapor UV radiation source emitting principally at 253.7nm. These VOCs include one aromatic organic, benzene; two chlorinated alkenes, trichloroethylene and tetrachloroethylene; four chlorinated ethanes, 1,1,2,2- tetrachloroethane, 1,1,1,2-tetrachloroethane, 1,1-dichloroethane, 1,2-dichloroethane;two chlorinated methanes, dichloromethane and carbon tetrachloride and two chlorinated propanes, 1,2-dichloropropane and 1,2,3-trichloropropane. The aromatic organic and chlorinated alkenes showed the highest reactivity during both direct photolysis and UV induced OH radical oxidation. There was little or no removal of the chlorinated alkanes when exposed to UV only. Degradation using UV/H₂O₂ AOP was evident among all 11 VOCs. Experimentally, 1,1, 2,2-terachloroethane showed the lowest reactivity along with carbon tetrachloride. A common feature among the two chemicals is that they have the highest number of chlorine atoms in the group which fundamentally affect their reaction with OH radicals. To ensure the effective degradation of all VOCs in a single UV AOP system, optimization and design of UV-based hydroxyl radical oxidation systems should be based on the most chlorinated VOCs if the new regulation is enforced. UV-based AOP should be used for those compounds most amenable to oxidation while other technologies fill in for the slower reacting compounds.

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