Study On Electro-oxidation Degradation Of Ofloxacin In Wastewater By BDD Electrode

Economic and social developments have resulted in an increased demand for antibiotics in the healthcare,livestock,and aquaculture industries.Some antibiotics used by these industries are inevitably released into the environment.Since antibiotics are not easily biodegradable,they cannot be completely removed from the environment using conventional treatment methods.The antibiotics in the environment pose risks to human health and ecological balance.Therefore,the development of a green and efficient water treatment process that can remove antibiotics from water is of considerable significance.Electrooxidation（EO）is an emerging wastewater treatment method that has attracted increasing attention.Among them,boron-doped diamond（BDD）electrodes have attracted people’s interest owing to their excellent electrochemical stability,wide potential window（2.75 V）,extremely high stability,and high corrosion resistance.Chloride ions are usually present in wastewater and can be used as a supporting electrolyte in electrooxidation processes.However,the role of active chlorine species produced near an electrode is often underestimated.In this study,the common antibiotic ofloxacin（OFX）was selected as the target pollutant.The OFX in the wastewater was treated using a BDD electrode system.This paper presents the development of a feasible method for treating the antibiotics present in wastewater.The main conclusions presented in this paper are as follows:（1）The OFX degradation rate was the highest when Na Cl was used as the supporting electrolyte.Its value was approximately seven times that of Na₂S₂O₈,Na₂SO₄,and Na NO₃ electrolyte systems.An increase in the current density of the electrode system accelerates OFX degradation.However,as the current density of the system increases,the energy consumption of the system also increases,and the current efficiency of the system decreases.The OFX degradation rate decreased with the increase in p H.The OFX degradation rate under acidic conditions was higher compared to alkaline conditions.（2）The optimum conditions for OFX degradation were determined using response surface optimization experiments.The optimum conditions determined were as follows:a reaction time of 10 min,an Na Cl concentration of 1.45 g/L,and a current density of18 m A/cm²,and the degradation rate of OFX was 100%.The simulation analysis of the operating cost of OFX degradation shows that although the cost of a BDD electrode system is eight times the cost of a Ti/Ru O₂ electrode,the average operating cost of degrading 1 g of TOC using a BDD electrode system is not much different from that of a Ti/Ru O₂ electrode system.The extent of degradation and mineralization ability of the BDD electrode system was better than those of a Ti/Ru O₂ electrode system.（3）The main free radical that is found in reaction systems and is predominantly involved in OFX removal is·OH.The amount of RCS produced was not large,and it mainly played an auxiliary role.Free chlorine（Cl₂,Cl O^-,and HCl O）also contributed to OFX degradation.Five possible degradation pathways were deduced,and among them,pathways 2 and 5 contained chlorinated by-products.The biological toxicity of most intermediates was lower than that of OFX.