PHOTOCATALYZED DEGRADATION OF AGROCHEMICALS IN TIO2 AQUEOUS SUSPENSIONS

The photocatalyzed degradation of ten agrochemicals (simazine, benthio carb, thiram, diazinon, fenitrothion, isoprothiolane, propyzamide, dic hlorvos, fenobucarb, and iprobenfos) has been investigated in an aqueo us suspension of TiO2 using a ultra high-pressure mercury lamp (lambda > 290 nm). The degradation is much faster than direct photolysis with out TiO2 and depends on the structures of the agrochemicals. As for ip robenfos, the effects of light intensity, wavelength, initial concentr ation, partial pressure of O-2 in bubbling gases, reaction temperature , and pH on the degradation rate are examined and a kinetic equation i s proposed to explain the experimental results. Several intermediates and probable pathways of the degradation are also proposed.