Removal of amoxicillin by UV and UV/H₂O₂ processes

The degradation of the β-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 10mM 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 80min (UV dose: 3.8×10^-3EinsteinL^-1) with the addition of 10mM 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 20min of contact time with a 10mM H₂O₂ dose after the complete elimination of AM, even though the UV/H₂O₂ advanced oxidation process led to bioactive photoproducts.