Photocatalytic transformations of hydrocarbons at the sea water/air interface under solar radiation

The kinetics and mechanisms of photocatalytic oxidation of dodecane and toluene have been considered in pure water and in synthetic sea water on different titanium dioxide powders under simulated solar radiation. Diluted hydrocarbons disappear in pure water in the presence of TiO2 and simulated solar radiation with a half live of ca. 2 h for dodecane (2.9 × 10−4 M) and 5 min for toluene (5.4 × 10−4M), respectively, and are mineralized for more than 95%. Possible mechanisms are presented based on detected intermediates and related systems. In synthetic sea water little changes in degradation rates are observed, probably attributable to modifications of the surface properties of the catalyst. No chlorinated compounds have been detected. Thin films of dodecane and dodecane/toluene mixtures have also been considered in the presence of TiO2 as micrometer powder, dispersed powder and silanized particles with hydrophobic properties. Whereas TiO2 P25 either naked or dispersed in 1-octanol, after initial activity at the water/oil interface sinks, leading to a decrease of efficiency, Aerosil T805 exhibits a sustained activity.