The effects and the toxicity increases caused by bicarbonate, chloride, and other water components during the UV/TiO 2 degradation of oxazaphosphorine drugs

Abstract

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.

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