TiO2-mediated photomineralization of 2-chlorobiphenyl:: The role of O2

Photocatalytic mineralization of 2-chlorobiphenyl (2-CB) in aqueous TiO(2) suspensions was conducted under four different oxygen partial pressures (Po(2)) in closed reactors. The observed O(2) adsorption equilibrium constant in TiO(2) aqueous suspension was 0.88 (kPa)(-1) based on the Langmuir-Hinshelwood rate function. Apart from the conventional electron-scavenging function, the dissolved oxygen was critical for the degradation of the hydroxyl intermediates, i.e., 2-chlorobiphenyl-ols and biphenyl-2-ol, which are potentially toxic. Degradation of 2-CB in the irradiated H(2)O(2) aqueous solutions under two different Pot was also studied for comparison. For UV/H(2)O(2), For does-not affect the removal of 2-CB, while reducing the Pot from 21 to 2 kPa resulted in 35% less CO(2) formation after 5 h irradiation. The similar O(2)-dependent destruction of the hydroxyl intermediates was also observed in the UV/H(2)O(2) system. We propose that molecular O(2) acts as a key reactant following the attack of a second OH radical during the ring opening in the degradation of the hydroxyl byproducts. (C) 2000 Elsevier Science Ltd. All rights reserved.