Comparison of the degradation of molecular and ionic ibuprofen in a UV/HO system.

The advanced oxidation technologies based on OH can effectively degrade the pharmaceutical and personal care products under operating conditions of normal temperature and pressure. In this study, direct photolysis of ibuprofen (IBU) is slow due to the relatively low molar extinction coefficient and quantum yield. Compared to direct photolysis, the degradation kinetics of IBU was significantly enhanced in the UV/HO system, mainly by OH radical mediated oxidation. In the UV/HO system, the degradation rate of ionic IBU was slightly faster than that of the molecular form. Kinetic analysis showed that the second-order reaction rate constant of ionic IBU (5.51 × 10 M s) was higher than that of the molecular form (3.43 × 10 M s). The pseudo first-order rate constant for IBU degradation (k) increased with increasing HO dosage. k can be significantly decreased in the presence of natural organic matter (NOM), which is due to (i) NOM radical scavenging effects (dominant role) and (ii) UV absorption. The degradation of IBU was inhibited by HCO, which was attributed to its scavenging effect. Interestingly, when NO was present in aqueous solution, a slight increase in the degradation rate was observed, which was due to NO absorbing photons to generate OH at a low quantum yield. No obvious effects were observed when SO and Cl were present.