Semiconductor-sensitized photodegradation of s-triazine and chloroacetanilide herbicides in leaching water using TiO2 and ZnO as catalyst under natural sunlight

In the present study, the photocatalytic degradation of five s-triazine (simazine, prometryn, terbutryn, atrazine and terbuthylazine) and three chloroacetanilide (propachlor, s-metolachlor, alachlor) herbicides in leaching water has been investigated. Zinc oxide (ZnO) and titanium dioxide (TiO2) were used as semiconductors at pilot plant scale under natural sunlight. The addition of an oxidant (Na2S2O8) to the semiconductor suspensions led to an increase in the rate of photooxidation. Comparison of catalysts showed that ZnO was the most efficient for catalyzing the removal of the studied compounds. Thus, more than 70% of the herbicide amount initially present in the leaching water was degraded after 240 min of illumination in the ZnO/Na2S2O8 system. Finally, some hydroxy and dealkylated derivatives of s-triazine herbicides were isolated during the experiment. (C) 2012 Elsevier B.V. All rights reserved.