Electrochemical Degradation Of Lamivudine And Sulfamethoxazole In Water By Modified Lead Dioxide Electrode

Pharmaceuticals have been widely detected in the environment as emerging organic pollutants,and studying their removal technologies and mechanisms are of great significance for evaluating their environmental risks.Previous studies have shown that electrochemical oxidation technology is a highly energy-efficient,versatile,and environmentally friendly technology,which has been successfully applied to degrade various refractory organic pollutants.In electrochemical degradation,the structure and performance of anode materials directly affect the degradation selectivity,rate and effect of pollutants.Therefore,the Pb O₂electrode modified by rare earth elements were selected in this paper,with antiviral drugs and antibiotics as target compounds,electrochemical oxidation degradation kinetics and mechanism of both were clarified,and the influence of several common anions in water on their degradation was investigated.The main research contents and results are as follows:（1）Lamivudine was selected as model compounds of antiviral drugs.Double-cathode and single-chamber were employed,and the electrodes Ti/Sn O₂-Sb/Ce-Pb O₂ and Ti plates were used as anodes and cathodes respectively to degrade lamivudine.The study found that the electrochemical oxidation degradation of lamivudine follows pseudo-first-order kinetics.The presence of HCO₃^-anion can effectively promote the electrochemical oxidative degradation of lamivudine,which may be caused by the CO₃·^-radical.The CO₃·^-radical was generated by HCO₃^-and it has strong selective oxidation on lamivudine;The presence of NO₃^-anion perform an inhibitory effect,may due to the competition of·OH between NH₃（generated by NO₃^-）and lamivudine.According to the measured degradation intermediates,the degradation pathway of lamivudine mainly includes the breaking of C-N bonds.After 4 h of electrochemical degradation,the total organic carbon（TOC）removal rate of lamivudine was 73.8%,39.5%of the sulfur atoms in lamivudine were released in the form of SO₄^2-,and the nitrogen atoms were converted into 34.3%NH₄⁺and 10.7%NO₃^-ion.（2）sulfamethoxazole（SMX）was selected as model compounds of antibiotics.The electrochemical degradation of SMX and its metabolite acetylsulfamethoxazole（Ac-SMX）by Ti/Sn O₂-Sb/Er-Pb O₂ electrode was studied.The results show that the electrochemical degradation of SMX and Ac-SMX follow pseudo-first-order kinetics.In the presence of high concentrations of Cl^-,the degradation of SMX and Ac-SMX was significantly accelerated,while the presence of NO₃^-inhibits the degradation of SMX and Ac-SMX.The degradation mechanisms of SMX and Ac-SMX include the breaking of S-N bonds,the opening ring of isoxazole and the nitration of amino groups.According to the quantitative structure-activity relationship（QSAR）model,the toxicity of SMX and Ac-SMX to aquatic organisms is significantly reduced after electrochemical degradation.Under different experimental conditions,the energy consumption of degrading 90%SMX and Ac-SMX was 0.58～8.97Wh/L and 6.88～44.19 Wh/L,respectively.Compared with the parent compound SMX,the metabolite Ac-SMX is more toxic and difficult to degrade,which highlights the importance of including its metabolites in research when studying wastewater treatment drugs.The electrochemical system composed of rare earth element-doped Pb O₂ electrode as anode can effectively degrade and mineralize lamivudine and sulfamethoxazole.After system optimization,it can be used as an efficient method for the degradation of antiviral drugs and antibiotics.