Removal of amoxicillin by UV and UV/H2O2 processes

The degradation of the beta-lactam antibiotic amoxicillin (AM) treated with direct UV-C and UV/H2O2 photolytic processes was investigated in the present study. In addition, the antibacterial activity of the solution treated by UV/H2O2 advanced oxidation was compared with AM solution treated with ozone. The degradation rate of amoxicillin in both processes fitted pseudo first-order kinetics, and the rates increased up to six fold with increasing H2O2 addition at 10 mM H2O2 compared to direct photolysis. However, low mineralization was achieved in both processes, showing a maximum of 50% TOC removal with UV/H2O2 after a reaction time of 80 min (UV dose: 3.8 x 10(-3) Einstein L-1) with the addition of 10 mM H2O2. The transformation products formed during the degradation of amoxicillin in the UV and UV/H2O2 processes were identified by LC-IT-TOF analysis. In addition, microbial growth inhibition bioassays were performed to determine any residual antibacterial activity from potential photoproducts remaining in the treated solutions. An increase of the antibacterial activity in the UV/H2O2 treated samples was observed compared to the untreated sample in a time-based comparison. However, the UV/H2O2 process effectively eliminated any antibacterial activity from AM and its intermediate photoproducts at 20 min of contact time with a 10 mM H2O2 dose after the complete elimination of AM, even though the UV/H2O2 advanced oxidation process led to bioactive photoproducts. (C) 2011 Elsevier B.V. All rights reserved.