Study On Enhanced Electrochemical Reduction Of Tetrabromobisphenol A By Modified Cathode Carbon Felt

Tetrabromobisphenol A（TBBPA）,as a typical bromine flame retardant,is stable and long-lasting.It can migrate and diffuse into the water body by the atmosphere.TBBPA enters the body during the biological uptake of water,which causes certain toxicity to various organs in the body.Therefore,the removal of TBBPA in water body is an urgent problem to be solved.Electrochemical reduction technology uses electrons as the reaction medium,it is often used to remove halogenated pollutants in water because it does not require reagents and is flexible and efficient.Carbon felt is often used as an electrode carrier.Because of its high hydrogen evolution overpotential and H^*production capacity,which needs to be further modified to improve electrode activity.In this paper,carbon felt is used as a carrier to prepare nano-scale Pd,Fe,Co（OH）₂ modified carbon felt electrodes,the electrochemical degradation efficiency on TBBPA of three prepared electrodes was studied,and the influence of different impact factors on the degradation effect of TBBPA was investigated;Finally,combining H^*inhibition experiments and LC-MS clarified the reduction mechanism and degradation pathways.The main research contents are as follows:Pd-C,Fe-C,Co（OH）₂-C electrodes were prepared by the constant current and constant voltage deposition method,and the metal loading was measured by Inductively Coupled Plasma Mass Spectrometry and Inductively Coupled Plasma Spectroscopy,the electrodes were characterized by Scanning Electron Microscope,Energy Dispersive Spectrometer,X-ray Photoelectron Spectroscopy,Linear Sweep Cyclic Voltammetry,Electrochemical Impedance Spectroscopy and other means.The characterization results show that Pd,Fe,and Co are deposited on the surface of the carbon felt,and the main components are nano-scale Pd⁰,Fe⁰ and honeycomb Co（OH）₂ nanosheets.The loading of Pd-C,Fe-C,and Co（OH）₂-C electrodes are 0.104 mg/cm²,2.75 mg/cm²,and 4.72 mg/cm²respectively;compared with carbon felt,the existence of three kinds of nano metal particles improve the limiting current density of the electrodes,and the charge transfer resistance is reduced.Pd-C,Fe-C,Co（OH）₂-C electrodes were applied to the electrocatalytic reduction of TBBPA.The results show that the degradation effect of TBBPA is affected by metal loading,cathode potential,initial concentration of TBBPA,p H value and other factors,the influence trends are different.Under the optimal conditions,the removal rates of Pd-C,Fe-C,and Co（OH）₂-C electrodes for 5 mg/L TBBPA within 60 minutes are 87.3%（-1.5 V）,43.7%（-1.0 V）,and 45.6%（-2.0 V）.The results of five repeated experiments show that the degradation effect of the three electrodes on TBBPA decreased by 4.1%,9.6%,3.9%,the stability of Pd-C electrode and Co（OH）₂-C electrode are prefect,Fe⁰ is easy to dissolve in acid solution,therefore Fe-C electrode’s stability is poor.Degradation mechanism studies have shown that the degradation of TBBPA by Pd-C and Fe-C electrode systems is the result of the combined effect of direct reduction caused by electron transfer on the electrode surface and indirect reduction dominated by H^*.The Co（OH）₂-C electrode reaction system is mainly the direct reduction process of electron transfer.Tri-BBPA,Di-BBPA,Mono-BBPA and BPA（intermediate products）were detected by HPLC-MS,which shows that the electrocatalytic reduction degradation of TBBPA is a gradual hydrodebromination process.The main reduction products of Pd-C,Fe-C,and Co（OH）₂-C electrodes are BPA,Mono-BBPA and Di-BBPA,respectively.The inhibition test qualitatively shows that the amount of H^*（E⁰=-2.1 V vs RHE）in different electrode systems determines the types of main reduction products of TBBPA.