Degradation of cyclophosphamide and 5-fluorouracil in water using UV and UV/H2O2: Kinetics investigation, pathways and energetic analysis

Abstract

The photodegradation of cyclophosphamide (CP) and 5-fluorouracil (5FU) in water was investigated by low-pressure UV and UV/H2O2 processes. The degradation effect of the two cytostatic drugs (CSDs) can be expressed using a pseudo first-order kinetic model in both UV and UV/H2O2 process. Their photodegradation effect in direct UV system significantly increases with the addition of H2O2 due to HO generation. At low H2O2 dose, the degradation efficiency of CSDs increases with oxidant concentration; however, excess H2O2 at higher dose reacts with HO and inhibits CSDs degradation. The optimal H2O2 dose is 0.2mM for both CSDs degradation based on the electrical energy analysis. The photodegradation effect of CSDs decreases in the presence of NOM, HCO3− or Cl−, and increases with NO3−. Treated water (TW) from a water treatment plant and secondary effluent (SE) from a wastewater treatment plant was employed as natural waters to evaluate the potential application of UV/H2O2. High concentration of alkalinity, NOM and Cl− in SE decreases the degradation efficiency of CSDs significantly. Transformation by-products of CSDs were detected to propose their potential degradation pathways.