The effect of solution pH and peroxide in the TiO₂-induced photocatalysis of chlorinated aniline

Chlorinated anilines are frequently used in the industry as starting materials for chemical synthesis. This type of compounds can end up as pollutants in wastewater. 2-Chloroaniline (2-ClA) was selected irradiating under monochromatic UV light at 300 nm. The reaction rate could be enhanced by introducing low level of H2O2into the UV/TiO2system. Excess H2O2could not increase the HO{radical dot} generation but retarded the reaction rate. The pH effect was also investigated in UV/TiO2and UV/TiO2/H2O2systems. All the experimental results show that pH is a sensitive parameter to the rate of degradation. Low reaction rate at acidic pH could be accounted by the dark adsorption test which has also proven the photocatalysis of TiO2may contribute to a two-step process: (1) 2-ClA pre-adsorbed onto TiO2and (2) photoexcitation of TiO2. At high pH, rate enhancement could be observed at UV/TiO2system because of the increase generation of HO{radical dot}. However, the introduction of H2O2slowdown the decay rate at such alkaline medium.