Kinetics and mechanism of TiO ₂ and ZnO based advanced oxidation processes for degradation of emerging contaminant levofloxacin

Abstract Levofloxacin (LEVO), a widely used fluoroquinolone antibiotic, is an emerging contaminant in water. In this study, degradation of levofloxacin by TiO 2 and ZnO photocatalytic advanced oxidation processes (AOPs) was investigated. Direct UV photolysis led to 21 % LEVO degradation, while UV/H 2 O 2 , UV/PMS and UV/PS resulted in 36, 60 and 76 % removal of LEVO (0.15 mM), in 60 min. Combination of TiO 2 and ZnO showed significant synergistic effect on UV/oxidant systems, indicated by 60, 75 and 90 % LEVO removal by UV/TiO 2 /H 2 O 2 , UV/ZnO/PMS and UV/ZnO/PS, respectively, in 60 min. The impact of reaction conditions, such as initial concentration of LEVO, oxidant concentration, photocatalysts loading, inorganic anions, solution pH etc. was investigated. The presence of inorganic ions significantly inhibited the degradation of LEVO. The FTIR analysis revealed the appearance of a large number of smaller degradation byproducts (DPs) during photocatalytic degradation of LEVO. Total organic carbon (TOC) analysis revealed 40, 61 and 75 % mineralization of LEVO by UV/H 2 O 2 /TiO 2 , UV/PMS/ZnO and UV/PS/ZnO systems, respectively, in 60 min. It was concluded that TiO 2 and ZnO photocatalytic advanced oxidation processes are efficient methods for the removal of emerging contaminants, such as levofloxacin from the water environment.