Sustainable degradation of ciprofloxacin in water by the electro-peroxone process via a graphite felt electrode system

Abstract Excessive, unregulated usage and reckless disposal of antibiotics have led to the formation of antibiotic resistance in bacteria. Additionally, untreated or partially treated pharmaceutical effluents are discharged into water bodies. With the increasing prevalence of antibiotic resistance across the globe, previously curable diseases are becoming challenging to handle due to the advent of superbugs. It is crucial to ensure complete treatment and removal of antibiotics and pharmaceuticals before discharging them into water bodies. Conventional treatment plants are not specialized in removing such complex, emerging contaminants. The advanced oxidation process is an emerging and promising treatment strategy for the abatement of emerging contaminants such as pharmaceutical compounds. This study explores an electrochemical advanced oxidation process, viz., electro-peroxone for treating ciprofloxacin, a model antibiotic drug. The electro-peroxone system houses electrodes of graphite felt that helps form hydrogen peroxide, an oxidant, in situ. The viability of the carbon-based graphite felt system in reactive oxygen species generation and ciprofloxacin degradation is investigated. A comparison of the electro-peroxone with two benchmark processes, namely, electrolysis and ozonation, is also carried out. Electro-peroxone and ozonation are both quite promising in removing the model contaminant. The in situ generation of H 2 O 2 and • OH is estimated. This is a one-of-a-kind study involving graphite felt as both anode and cathode and achieves an in situ generation of H 2 O 2 of 47 mg/L in 120 min and • OH of 140 µM within 60 min of electro-peroxone. Besides, the efficacy of the system in contaminant degradation is examined at voltammetric and galvanostatic modes of operation. Ozonation and electro-peroxone processes achieved an efficiency between 97% and complete removal of ciprofloxacin in less than an hour. This novel system generates several times higher hydrogen peroxide than the existing graphite electrode system, making it more efficient in radical generation and pollutant abatement. This graphite felt-based electro-peroxone system, on further optimization and up-scaling, can be a promising strategy for abating pharmaceutical compounds and effluents. Graphical Abstract