| As an environmentally friendly technology,electrochemical reduction technology has become a research hotspot of chlorinated organic compounds due to its ability to remove chlorine atoms in a targeted way.However,the current research on the treatment of wastewater containing chlorinated organic compounds by electrochemical reduction technology has problems such as poor degradation of pollutants or poor electrode stability due to the complex synthesis of cathode materials.Therefore,the selection of electrode materials with easy access and low cost and the optimization of their use need to be further studied.In order to achieve efficient degradation and dechlorination of chloramphenicol（CAP）,a typical chlorinated organic compounds of pharmaceutical and personal care products（PPCPs）,this topic constructed a simple electrochemical system,which mainly explored the establishment and optimization of the electrochemical reduction system and the degradation effects of chloramphenicol in this system,the stability of the system,the pathway and mechanism and toxicity analysis of CAP degradation.The screening results of commercial electrode materials showed that carbon felt cathode showed the best CAP degradation effect.Cyclic voltammetry results showed that a significant reduction peak appeared at-0.4V（vs.SCE）with the presence of CAP,indicating that cathodic reduction of CAP might have occurred on the surface of carbon felt electrode.The fitting result of the reaction kinetic model showed that the degradation process of CAP in electroreduction system with carbon felt cathode conformed to the first-order reaction kinetic model.The optimal removal rate of CAP was achieved under the conditions of cathode potential of-1.4 V（vs.SCE）,p H of 7,electrolyte type of 50 m M NaClO4,complete removal of CAP was achieved within 60 min and the degradation rate constant reached 0.162 min-1.After electrolysis at different initial concentrations of CAP for 60 min,CAP was efficiently removed and the degradation rate constant of CAP reached 0.147～0.171 min-1.Cathode dechlorination in the electroreduction system continued in the whole electrolysis time,and the conversion rate of Cl-reached 60.5% at 60 min.Cl element was continuously removed and generated Cl-in electroreduction system with carbon felt cathode.The microstructure of carbon felt cathode was observed and analyzed by scanning electron microscope（SEM）,and electrochemical performance of carbon felt electrode for CAP continuous removal was proved by repeated experiments.The addition of 2 m M peroxymonosulfate（PMS）enhanced the mineralization effect of carbon felt cathode on CAP degradation,and Total organic carbon（TOC）removal rate reached 69.7% after 240 min.Five kinds of intermediate products in the degradation process of CAP were analyzed by liquid chromatography-mass spectrometry.The electron spin resonance technology（ESR）and quenching experiments have proved the existence of active hydrogen atoms,and the degradation mechanism of CAP in electroreduction system with carbon felt cathode was proposed.The rapid removal of CAP was realized mainly through the indirect reduction of active hydrogen atoms and the direct reduction of electrons.Through the calculation of density functional theory,the active sites that were easy to be attacked of CAP were explored and the feasibility of the degradation path of dechlorination process was verified.The toxicity prediction results of ECOSAR software on CAP and its products showed that the toxicity of the original pollutants could be effectively reduced in electroreduction system with carbon felt cathode.This study provides a new option for material and idea for efficient degradation of CAP by the electroreduction system with carbon felt cathode.The electroreduction system with carbon felt cathode achieved the degradation of CAP through the dechlorination process.This subject provides theoretical support for the electrochemical reduction technology to remove chlorinated organic compounds of PPCPs. |
