Radiolytic degradation of ornidazole in aqueous solutions by electron beam irradiation: Implications to parameters, kinetics, toxicity and cost evaluation

Abstract

The study is aimed to assess the effectiveness of electron beam (EB) technology to degrade the antibiotic ornidazole (ORN) in aqueous solution. The influence of several factors viz. initial ORN concentrations, dose, pH of solution, and addition of NO2−, NO3−, isopropanol, H2O2, thiourea, and different water mediums were evaluated on the ORN degradation. The degradation of ORN was followed by pseudo first-order reaction kinetics with rate constant value of 2.01, 1.17, 0.87 and 0.70 kGy−1 for the initial concentrations of 25, 50, 75, and 100 mg L−1 with their corresponding (G-(ORN)) values of 0.93, 1.60, 1.97, and 2.12 μmol J−1, respectively. The presence of NO2−, thiourea and isopropanol revealed reduction in the k-value, whereas, addition of NO3− anion had not substantially effected the degradation of ORN. Presence of H2O2 exhibits significant effect on the mineralization efficiency of ORN rather than degradation extent. The efficacy of EB irradiation to degrade ORN decreased in wastewater in comparison to surface, ground and ultrapure water. Based on the LC-QTOF-MS study, it could be ascribed that degradation of ORN was primarily due to the oxidative species HO radical and direct cleavage of ORN compound. Tentative pathways for EB-induced radiolytic degradation of ORN were proposed. Cytotoxicity assessment and overall cost of electrical energy consumed for the degradation of ORN was also evaluated.