In the present work, degradation of chlorpyrifos in water was investigated using semiconductor oxide catalysts, i.e. zinc oxide (ZnO) and titanium dioxide (TiO2). The influence of various parameters, such as type of the catalyst, irradiation time, catalyst concentrations, pH, and sodium bicarbonate salt was also studied. Results indicated that the optimal concentration of the catalyst was 0.15 g/L. It was also found that TiO2 is a better catalyst than ZnO under the same photocatalytic reaction conditions. The highest removal efficiency was achieved at pH 9. Results from the present study suggested that the photodegradation efficiency of pesticides increases with the increase of the illumination time. The photodegradation efficiency of chlorpyrifos was found to be 80% and 90% for UV/ZnO and UV/TiO2, respectively. Photodegradation in the presence of sodium bicarbonate was slower in comparison to that without the salt. In addition, the efficiency of photocatalytic degradation in distilled water was higher than in natural water
