Web Release Date: March 18,
Treatment of Volatile Organic Chemicals on the EPA Contaminant Candidate List Using Ozonation and the O3/H2O2 Advanced Oxidation Process
and
Department of Environmental Health Sciences, Environmental Science and Engineering Program, University of California at Los Angeles, Los Angeles, California 90095, and Department of Civil and Environmental Engineering, Duke University, Durham, North Carolina 27708
Received for review October 3, 2005
Revised manuscript received February 16, 2006
Accepted February 27, 2006
Abstract:
Seven volatile organic chemicals (VOCs) on the EPA Contaminant Candidate List together with 1,1-dichloropropane were studied for their reaction kinetics and mechanisms with ozone and OH radicals during ozonation and the ozone/hydrogen peroxide advanced oxidation process (O3/H2O2 AOP) using batch reactors. The three aromatic VOCs demonstrated high reactivity during ozonation and were eliminated within minutes after ozone addition. The high reactivity is attributed to their fast, indirect OH radical reactions with kOH,M of (5.3-6.6) × 109 M-1 s-1. Rates of aromatic VOC degradation are in the order 1,2,4-trimethylbenzene > p-cymene > bromobenzene. This order is caused by the selectivity of the direct ozone reactions (kO3,M ranges from 0.16 to 304 M-1 s-1) and appears to be related to the electron-donating or -withdrawing ability of the substituent groups on the aromatic ring. The removal rates for the five aliphatic VOCs are much lower and are in the order 1,1-dichloropropane > 1,3-dichloropropane > 1,1-dichloroethane > 2,2-dichloropropane > 1,1,2,2-tetrachloroethane. The second-order indirect rate constants for the aliphatic VOCs range from 0.52 × 108 to 5.5 × 108 M-1 s-1. The relative stability of the carbon-centered intermediates seems to be related to the relative reactivity of the aliphatic VOCs with OH radicals. Except for 1,3-dichloropropane, ozonation and the O3/H2O2 AOP are not effective for the removal of other aliphatic VOCs. Bromide formation during the ozonation of bromobenzene indicates that bromate can be formed, and thus, ozonation and O3/H2O2 AOP may not be suitable for the treatment of bromobenzene.
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