Degradation of antibiotics by modified vacuum-UV based processes: Mechanistic consequences of HO and KSO in the presence of halide ions.

In this work, the degradation of cefalexin, norfloxacin, and ofloxacin was examined via various advanced oxidation processes (AOPs). Direct photolysis by ultraviolet (UV) and vacuum ultra violet (VUV) was less effective for the degradation of fluoroquinolone antibiotics such as norfloxacin and ofloxacin than that of cefalexin. Both hydrogen peroxide (HO) and potassium persulfate (KSO) assisted UV/VUV process remarkably enhanced fluoroquinolone degradation. The addition of KSO was superior to HO under VUV irradiation, with the best removal efficiency of norfloxacin and ofloxacin being almost 100% within 3 min in the presence of VUV/KSO. The ofloxacin degradation rate was accelerated as concentrations of HO and KSO was increased to 3 mM, but the degradation rate was slightly decreased with excess HO (>3 mM). The performance of modified VUV processes (i.e., VUV/HO and VUV/KSO) was inhibited at highly alkaline condition (pH 11). The co-existence of halides (Cl and Br) enhanced antibiotics degradation via the modified VUV processes, but the reaction was almost unaffected in the presence of single halides. This study demonstrated that modified VUV processes (especially VUV/KSO) are efficient for eliminating fluoroquinolone antibiotics from water, which can be considered as a clean and green method for the treatment of antibiotics-containing industrial wastewater.