The effects and the toxicity increases caused by bicarbonate, chloride, and other water components during the UV/TiO2 degradation of oxazaphosphorine drugs.

The influences of HCO3-, Cl-, and other components on the UV/TiO2 degradation of the antineoplastic agents ifosfamide (IFO) and cyclophosphamide (CP) were studied in this work. The results indicated that the presence of HCO3-, Cl-, NO3-, and SO42- in water bodies resulted in lower degradation efficiencies. The half-lives of IFO and CP were 1.2 and 1.1 min and increased 2.3-7.3 and 3.2-6.3 times, respectively, in the presence of the four anions (initial compound concentration = 100 μg/L, TiO2 loading =100 mg/L, anion concentration = 1000 mg/L, and pH = 8). Although the presence of HCO3- in the UV/TiO2/HCO3- system resulted in a lower degradation rate and less byproduct formation for IFO and CP, two newly identified byproducts, P11 (M.W. = 197) and P12 (M.W. = 101), were formed and detected, suggesting that additional pathways occurred during the reaction of •CO3- in the system. The results also showed that •CO3- likely induces a preferred ketonization pathway. Besides the inorganic anions HCO3-, Cl-, NO3-, and SO42-, the existence of dissolved organic matter in the water has a significant effect and inhibits CP degradation. Toxicity tests showed that higher toxicity occurred in the presence of HCO3- or Cl- during UV/TiO2 treatment and within 6 h of reaction time, implying that the effects of these two anions should not be ignored when photocatalytic treatment is applied to treat real wastewater.