The effects of inorganic anions and organic matter on mesotrione (Callisto®) removal from environmental waters

Abstract

The photocatalytic elimination of the herbicide mesotrione from the commercial formulation Callisto® in environmental and synthetic waters by means of heterogeneous advanced oxidation processes was investigated. The activities of the commercial photocatalyst TiO2 Degussa P25 (TiO2) and ZnO in the degradation of mesotrione under UVA and simulated sunlight in doubly distilled, ground and in river water was compared. Environmental waters as the matrix significantly lowered the removal rate (by about 4 and 1.5 times for TiO2 and ZnO, respectively) under UVA irradiation. Besides, the organic additives from Callisto® also reduced the degradation rate of mesotrione. The effects of inorganic anions (Cl-, SO42- and HCO3-) and humic acid (HA), which were identified as major species in ground and river water, was evaluated. It was found that  (pH ≈4 and ≈8) and HCO3- (pH ≈8) using TiO2 mainly accelerated the degradation rate of mesotrione, while SO42- had the opposite effect at pH ≈4 and did not affect the degradation rate at pH ≈8. Furthermore, HA mainly did not significantly affect the degradation rate of mesotrione at pH ≈4 and ≈8. Moreover, almost all anions, and HA slightly inhibited the degrad­ation rate of mesotrione in synthetic water using ZnO.