Electrochemical degradation of levofloxacin in synthetic hospital effluents: insights into operating parameters, by-products formation and toxicity
Ana Hayat, José Leandro da Silva Duarte, Fermín Cruz-Gómez, Carmen M. Domínguez, Aurora Santos, Salvador Cotillas
Abstract
This study investigates the electrochemical degradation of the broad-spectrum antibiotic levofloxacin (LVX) in synthetic hospital effluents using two different anode materials: Boron-Doped Diamond (BDD) and RuO 2 /Ti. Experiments were performed under a range of current densities (5-50 mA cm −2 ) to assess removal efficiency, reaction kinetics, intermediate by‐product formation, and effluent toxicity. The degradation process was modelled using first-order kinetics, revealing that complete LVX removal is achievable under optimised operating conditions. BDD anodes demonstrated higher degradation efficiency at lower current densities, whereas RuO 2 /Ti anodes required higher values to attain comparable degradation rates. Detailed analyses of electrogenerated oxidants and intermediate compounds indicated that direct oxidation at the anode surface and mediated oxidation via hydroxyl radicals and other reactive species contribute significantly to the degradation mechanism. Additionally, the breakdown of organics in the effluent resulted in the release of nitrogen, primarily as nitrate, which is subsequently reduced to ammonium and further reacts with hypochlorite to form chloramines, thereby enhancing the degradation process, mainly when using RuO 2 /Ti anodes. Mineralisation studies showed that Total Organic Carbon (TOC) removal exceeded 80 % with BDD anodes. Toxicity evaluations, conducted in vitro and silico methods, confirmed that most of the by-products generated during treatment pose minimal environmental risk. These findings underscore the potential of electrochemical oxidation as a sustainable and robust technology for the remediation of pharmaceutical contaminants in hospital effluents.