The photocatalytic degradation of atrazine on nanoparticulate TiO2 films

The photocatalytic removal of atrazine from water was investigated using immobilised TiO2 films in a stirred tank reactor designed to maximise mass transfer. The degradation of atrazine was demonstrated with a number of breakdown products identified including the stable end product cyanuric acid. The process was monitored using high performance liquid chromatography (HPLC), total organic carbon analysis (TOC) and liquid chromatography–mass spectrometry (LC–MS). A decrease in the TOC was observed and attributed to the oxidative degradation of atrazine side chains. Intermediates identified included 2-chloro-4-acetamido-6-isopropylamino-1,3,5-triazine, 2-chloro-4-ethylamino-6-(1-methyl-1-ethanol)amino-1,3,5-triazine, 2-chloro-4-ethylamino-6-(2-propanol)amino-1,3,5-triazine, 2-hydroxyatrazine, desethylatrazine, deisopropylatrazine, 2-hydroxydesethyl atrazine and cyanuric acid. Operational parameters such as catalyst loading, oxygen concentration, initial pollutant concentration and UV source were investigated. Atrazine removal followed first order kinetics and the rate was dependent upon catalyst loading up to an optimum loading (above which a decrease in the degradation rate was observed). No difference in the rate was observed when either air and O2 sparging was used. The rate was directly proportional to initial concentration in the range studied. The use of UVB irradiation did not appear to increase the rate of degradation in comparison with UVA irradiation. However, the maximum apparent quantum yield for the photocatalytic degradation was higher under UVB (0.59%) compared to UVA (0.34%).