Gas-phase photocatalytic degradation of trichloroethylene and formation of reaction products on immobilized titanium dioxide
Abstract
The main research objective was to investigate gas-phase photocatalytic degradation of trichloroethylene over immobilized anatase TiO$\sb2$ thin film inside periodic rib-roughened photocatalytic annular reactors illumined with near-UV light. Research efforts were focused on designing and evaluating bench scale available photocatalytic annular reactors, identifying and quantifying photocatalytic degradation intermediates/products from photocatalysis of TCE vapor, investigating photocatalysis reaction mechanisms, proposing possible degradation or formation scheme of chlorinated organic pollutants, and developing heterogeneous reaction model to simulate the photocatalysis of TCE vapor in the photocatalytic annular reactors. Some possible photocatalysis affecting factors including reactant concentrations, water vapor content, and reaction time were also examined. High conversion of TCE in short reaction time was successfully demonstrated by tested photocatalytic annular reactors. Enhancement of TCE conversion could be accomplished by increasing oxygen concentrations as well as reactor space times and reducing mass transfer resistance with inserting turbulence promoters inside photocatalytic reactors. However, dramatic inhibition of the photocatalysis of TCE was observed in the presence of water vapor. At least nine chlorinated organic compounds and two predominant Cl-containing inorganic species were identified from photocatalysis of TCE. The possible reaction scheme involving oxygen oxidation, chlorination, Cl subtraction, carbon-carbon cleavage, and proton subtraction and addition reactions for the photocatalytic degradation of TCE and formation of chlorinated organic intermediates/products was proposed in this investigation. The species that might have had an important role in the overall photocatalytic process observed might have been H, Cl, and O atoms, hydroxyl radicals, and various organic radical intermediates. Inhibition of chlorination reaction of organic species is expected to take place in the presence of higher oxygen concentrations.
Degree
Ph.D.
Advisors
Marinas, Purdue University.
Subject Area
Civil engineering|Chemical engineering
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