Electron beam induced degradation of ofloxacin in aqueous solution: Kinetics, removal mechanism and cytotoxicity assessment

This study is focused on the assessment of potency of electron beam (EB) irradiation for the degradation of fluoroquinolone antibiotic ofloxacin (OFC) in aqueous medium. The influence of parameters like, initial concentration, solution pH, and presence of various additives viz., NO3, NO2, propanol, thiourea, H2O2 and different water matrices were examined on the degradation of OFC. The degradation followed the pseudo first-order reaction kinetics with dose constant values of 1.861, 0.917, 0.659 and 0.540 kGy(-1) for the following initial concentrations: 0.05, 0.1, 0.15 and 0.2 mmol L-1 with their corresponding (G(-OFC)) values of 0.389, 0.600, 0.779 and 0.936, respectively. OFC degradation in the presence of different additives showed decrease in the dose constant, mainly owing to the competition reactions of OFC and other scavengers with the radiolytically generated reactive radical species, especially HO center dot radicals. Addition of H2O2 exhibited synergistic effect on OFC degradation and mineralization extent. The effectiveness of EB prominently reduced in wastewater when compared to ultrapure, surface and ground water due to the higher scavenging rates of the reactive species. Based on the Gaussian calculations and LC-QTOF-MS analysis, it was inferred that OFC radiolytic degradation was mainly attributed to oxidative HO center dot radicals and the direct cleavage of OFC molecules. Possible removal pathways for OFC using EB irradiation were proposed with identification of almost twenty one transformation products. The OFC transformation products did not exhibited any cytotoxicity even at 1.0 kGy dose, ensuring the ability of EB technology to make water reusable and recyclable for several applications.