Carbamazepine degradation by UV and UV-assisted AOPs: Kinetics, mechanism and toxicity investigations

Carbamazepine (CBZ), a widely used antiepileptic drug, was removed by UV-254 nm based advanced oxidation processes. CBZ was found to be stable under sole UV, however, removal of CBZ was promoted using Fe-and Fe2+ with UV. Further, removal efficiency of CBZ was significantly enhanced by coupling H2O2 with UV and Fe3+/Fe2+. At 3600 mJ cm(-2), 7.5, 60.2, 74.3 and 90.6% CBZ degradation was achieved in UV, UV/H2O2, UV/H2O2/Fe3+ and UV/H2O2/Fe2+., using CBZ, H2O2, Fe2+ and Fe3+ at 21.16, 1060.00, 17.91 and 17.91 mu M, respectively. Higher CBZ degradation in the presence of H2O2 was attributed to HO center dot whose second-order rate constant with CBZ was calculated to be (8.83 +/- 0.27) x 10(9) M-1 s(-1). Removal of CBZ by UV/H2O2/Fe2+ system was optimum at pH 3.0, as 80.8, 90.6 and 70.4% CBZ degradation was observed at pH 2.0, 3.0 and 6.5, respectively. The removal of CBZ by UV/H2O2/Fe2+ was retarded in the presence of Cl-and humic acid as revealed from 84.5 and 56.7% CBZ degradation in the presence of Cl-and humic acid, respectively, compared to 90.6% in their absence at 3600 mJ cm(-2). The CBZ degradation products were found to be less toxic than the parent compound, suggesting important role of UV-assisted AOPs in efficient removal and toxicity reduction of CBZ and their degradation products. (C) 2018 Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.