Photocatalytic activity of synthesized nanosized TiO2 towards the degradation of herbicide mecoprop

The kinetics and possible mechanism of the photocatalytic degradation of herbicide mecoprop, in UV illuminated aqueous colloids of synthesized nanosized TiO2 were investigated. The rate of degradation was studied by H-1 NMR, UV spectrometry, as well as by potentiometric titrimetric determination of generated chloride. The catalyst dosage and effects of other kinetic factors on the photocatalytic degradation, such as initial substrate concentration, temperature and type of TiO2 were investigated as well. The degradation rates were found to be strongly influenced by the above parameters. It was found that photocatalytic efficiency is lower and that a smaller number of observed organic intermediates (only 4-chloro-2-methylphenol and acetic acid) was detected than those observed in the presence of TiO2 (Degussa P-25). Kinetics of the degradation were also monitored for direct photolysis, as well as for solar degradation in the presence and in the absence of TiO2. (C) 2004 Elsevier B.V. All rights reserved.