Comparison of Liquid and Gas-Phase Photooxidation of MTBE: Synthetic and Field Samples

Abstract

The feasibility of photooxidation treatment of methyl \Itert\N-butyl ether (MTBE) in water was investigated using two systems: (1) a slurry falling film photoreactor and (2) an integrated air stripping with gas phase photooxidation system. Methyl \Itert\N-butyl ether-contaminated synthetic water and field samples from contaminated sites were used for these studies. Using a TiO\d2 slurry (0.1 g/L; Degussa P25) flowing down at a rate of up to 0.26 L/min over the inner surface of a glass tube surrounding a 1-kW medium pressure mercury lamp, more than 99% of MTBE in the synthetic samples, initially at 1 mg/L, was degraded within 90 min. The major degradation products from MTBE were \Itert\N-butyl alcohol, \Itert\N-butyl formate, and small amounts of acetone. However, the degradation of MTBE and its byproducts in contaminated groundwater samples was hindered significantly by dissolved metals uch as Fe\U2+\N, chloride ions, and aromatic organic species. Integrating air stripping with gas-phase photocatalysis is an effective alternative that would not be affected by the water chemistry. The reaction rates for MTBE degradation in the gas phase are orders of magnitude faster than in aqueous solution.