The photocatalytic oxidation of low concentration MTBE on titanium dioxide from groundwater in a falling film reactor

This study is focused on three main objectives: 1) to determine the feasibility of using a falling film slurry photocatalytic reactor for the degradation of methyl tertiary-butyl ether (MTBE) in water, 2) to assess tbefeasibility of MTBE photo-oxidation on TiO2 at low initial MTBE concentrations (< 1 mg/L, and 3) to compare the effectiveness of MTBE pboto-oxidation on TiO2 in synthetically-contaminated water, and in actual MTBE-contaminated groundwater samples. The MTBE degradation rates observed in a laminar falling film photocatalytic reactor for synthetic samples, with concentrations ranging from 50 mug/L to I mg/L, were high, achieving nearly complete (99(+)%) degradation of 1 mg/L MTBE and its byproducts in less than 120 minutes. The calculated single-pass conversions were as high as 60%, corresponding to residence times of approximately 5 seconds in the falling film reactor. The observed degradation products of MTBE oxidation were predominantly tert-butyl alcohol (TBA) and tertbutyl formate (TBF). However, tests conducted using groundwater samples showed significantly reduced photoactivity of TiO2 towards the degradation of MTBE. Aromatic species and dissolved metal and chloride ions present in the field samples compete with MTBE and molecular oxygen on the TiO2 surface, and hence delay and retard MTBE degradation.