EARTH

[31013-24-10] Degradation of molecule and ionic ibuprofen in UV/H₂O₂ system

○Rongkui Su¹, Zhihui Yang -¹, Liyuan Chai - ¹, Chongjian Tang -¹, Bo Li -¹ (1. Central South University)

Chairman: Suwat Athichanagorn （Chulalongkorn University）, Min Xiabo (Central South University)

Keywords:Hydroxyl radical, molecule form, ionic form, ibuprofen, kinetics

The advanced oxidation technology based on hydroxyl radical (^•OH) can directly remove the pollutants or through oxidation to improve the biodegradability of sewage at ambient temperature and pressure. In this study, the degradation kinetics of ibuprofen (IBU) was significantly enhanced in the UV/H₂O₂ system. The IBU degradation mainly contributed to ^•OH radical mediated oxidation, accounting for 97% of IBU degradation. The direct UV photolysis of ionic form IBU was faster than molecule form due to the higher molar absorption coefficient and quantum yield for ionic form IBU. In the UV/H₂O₂ system, the degradation rates of ionic form IBU was also slight faster than molecule form. The main determinants were the secondary reaction rate constants of IBU with ^•OH and the amount of ^•OH. The second order rate constants of molecule form and ionic form IBU with ^•OH were 3.43 × 10⁹ M^-1s^-1and 5.51 × 10⁹ M-1s-1 at pH 3 and pH 7.55, respectively. Pseudo first-order rate constant for IBU degradation (k_obs) increased with increasing the dosage of H₂O₂, while natural organic matter (NOM) significantly decreased k_obs due to the effects of radical scavenging and UV absorption with the former one being dominant. The degradation of IBU in the UV/H₂O₂ system was not affected by the addition of sulfate ion and chloride ion, while a slight increment of the degradation rate was observed in the presence of nitrate ion since nitrate ion absorbs UV photons and then ^•OH can be generated at a low quantum yield.