Study On The Promotion Mechanism Of Tetracycline Degradation By Electro-fenton Based On Controlling The Reaction Zone

Tetracycline has become the world’s largest,most polluting and most threatening antibiotic.However,since tetracycline can inhibit the growth and reproduction of microorganisms such as bacteria,the traditional sewage treatment technology has been greatly limited.The electro-Fenton technology has been widely concerned because of its simple operation,green and efficient,and good removal effect.However,in the electro-Fenton system,the pollutants are mainly distributed in the main body of the liquid phase,while H₂O₂ is generated near the cathode.Therefore,the reactive substance·OH produced by H₂O₂ is also mainly distributed near the cathode,and the existence life of·OH in the solution is extremely short and cannot be diffused for a long distance.The diffusion of·OH to the main body of the liquid phase to degrade pollutants will inevitably lead to a large number of ineffective consumption of free radicals,which will seriously affect the degradation efficiency of pollutants.Therefore,this study enriched pollutants by N-doped modified activated carbon and controlled the reaction area of·OH catalytic degradation of tetracycline in the production area of·OH,that is,the reaction area control was proposed.The key to realize the control of the reaction area is the adsorption performance of the cathode material.Activated carbon is cheap and easy to obtain and has superior adsorption performance.It is a good electrode material.In addition,N-doping modification shows excellent effect on improving the adsorption performance and 2e-ORR selectivity of carbon materials.Therefore,in this study,a N-doped modified activated carbon cathode was successfully prepared by high-temperature activation method.The activated carbon before and after modification was characterized by scanning electron microscopy（SEM）,N₂ adsorption-desorption experiments and X-ray photoelectron spectroscopy（XPS）.The effect of N-doping on the adsorption of tetracycline by activated carbon cathode and the ability to improve the selectivity of 2e-ORR were investigated by adsorption experiments and electrochemical experiments.Finally,the mechanism of different N-doping types on the cathodic adsorption performance and 2e-ORR selectivity of activated carbon was revealed by cross-scale simulation.The characterization results showed that the surface morphology of activated carbon changed significantly after modification,the pore volume and specific surface area(S_BET)increased significantly,and N element was successfully introduced into activated carbon.Electrochemical experiments show that the electron transfer number of NAC-1100/GF cathode is closer to 2,which means that its 2e-ORR selectivity is the best.Adsorption experiments showed that NAC-1000/GF cathode had the best adsorption effect on tetracycline,reaching35.45%.In addition,quantum chemistry and molecular dynamics simulations show that pyrrolic-N and pyridinic-N are the decisive factors for the improvement of tetracycline adsorption capacity of modified activated carbon,while pyridinic-N and graphitic-N play a crucial role in promoting 2e-ORR selectivity.The electro-Fenton comprehensive experiment clarified the optimal reaction conditions of the electro-Fenton system.Under the optimal reaction conditions,the removal rate of tetracycline by the modified cathode was significantly higher than that before modification.Among them,NAC-1000/GF has the best degradation effect,reaching 83.07%,because NAC-1000/GF has the highest adsorption performance and relatively high 2e-ORR selectivity.In addition,after further analysis of the experimental data,it was found that the reaction zone control was successfully realized in this study,and under the control of the reaction zone,there was an efficient synergistic effect between adsorption and 2e-ORR.