Fipronil decomposition in aqueous semiconductor suspensions using UV light and solar energy

• Photocatalytic oxidation of fipronil in water.
• The study was performed using ZnO and TiO2 under solar and artificial irradiation.
• The best photocatalytic efficiency was obtained under UV artificial light.
• Fipronil was almost totally degraded using ZnO/Na2S2O8, ZnO, TiO2/Na2S2O8 and TiO2.
• Four intermediates were identified.

The photocatalytic degradation of fipronil in drinking water was studied using zinc oxide (ZnO) and titanium dioxide (TiO2) as photocatalyst under irradiation by solar and artificial light. Photocatalytic experiments showed that the addition of semiconductors in tandem with the oxidant (Na2S2O8) strongly enhances the degradation rate of fipronil in comparisons carried out with photolytic experiments under artificial light. However, under solar irradiation, the photocatalytic decomposition of fipronil occurs very slowly. The residual levels of fipronil for ZnO/Na2S2O8 and TiO2/Na2S2O8 after 60 min of illumination at a constant volumetric rate of photon absorption in the photoreactor were 0.8 and 1.5 μg/L, respectively. The main intermediates (fipronil-sulfone, fipronil-sulfide, fipronil-desulfinyl and fipronil-carboxamide) detected during the degradation of fipronil in water were identified.