Langmuir Parameters and Destruction Rates of Organic Compounds Over Near-Ultraviolet Illuminated Titanium Dioxide
The photocatalytic oxidation rates to carbon dioxide of twenty two common organic contaminants in water were determined under identical conditions using a thin film of titanium dioxide illuminated with a 20 W blacklight fluorescent tube. The oxidation rates of each solute over a wide range of concentrations obey Langmuir-Hinshelwood kinetics with reasonable precision. The Langmuir parameters were determined and their significance is discussed in terms of adsorption and reaction characteristics. Oxidation rates for low- and high- concentration solutions were calculated, and the importance of adsorption characteristics is shown for the removal of low concentrations of impurities. A convenient general relationship for all solutes is shown to be an approximate adherence to apparent first-order kinetics for the disappearance of the solute. The apparent first-order rate constant are useful in comparing efficiencies of various photocatalysts and geometric arrangements of photocatalyst and light source. Photoreactors combining removal of impurities by adsorption with in situ destruction of the adsorbed impurities and regeneration of the adsorbent are described and some performance details given.