Photocatalytic Degradation of Herbicide Isoproturon in TiO2 Aqueous Suspensions: Study of Reaction Intermediates and Degradation Pathways

Heterogeneous photocatalytic degradation and mineralization of Isoproturon (IPU) was investigated in aqueous solutions containing titanium dioxide. The degradation was monitored by observing the change in absorption intensity in UV range and through HPLC analysis. The degradation rate was found to be strongly dependent on catalyst concentration, initial pH, and substrate concentration. The effect of variation in intensity of UV irradiations, catalyst recycling as well as area/volume is also studied for the practical applications. The degradation rate was observed to follow first-order kinetics. TiO2 loading 0.5 g L-1, pH 5.0, C-0 = 25 mg L-1 were the optimized conditions for obtaining the better degradation rates. Reduction in COD and TOC values along with the generation of ammonium further indicated the mineralization of the IPU. Fixed bed studies on glass sheet and small cement slabs eliminates the drawbacks of slurry mode photocatalysis. An attempt was also made to identify the intermediates (degradation products) through LC-MS analysis. (c) 2013 American Institute of Chemical Engineers Environ Prog, 33: 402-409, 2014