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 240min of illumination in the ZnO/Na2S2O8 system. Finally, some hydroxy and dealkylated derivatives of s-triazine herbicides were isolated during the experiment. ► Heterogeneous photocatalytic oxidation of herbicides in water. ► ZnO and TiO2 strongly enhanced photodegradation in comparison with photolysis. ► ZnO was the most efficient for catalyzing the removal of these compounds. ► Hydroxy and dealkylated derivatives of triazine herbicides were isolated.
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