Degradation Mechanism Of Bisphenol Organic Compounds By Oxygen-doped Porous Carbon Electro-fenton Cathode Derived From Distiller’s Grains

Bisphenols（BPs）organic compounds are typical environmental endocrine disrupting chemicals（EDCs）that are difficult to degrade and widely exist in water environment.Among them,bisphenol A（BPA）and bisphenol S（BPS）are one of the EDCs with high detection frequency and contents at present.Studies have shown that even exposure to low BPs doses will lead to various adverse health effects on the human body and aquatic organisms.Therefore,the removal of BPs in wastewater is of great significance for maintaining human health and the ecological environment.Electro-Fenton advanced oxidation technology,through H₂O₂generated from the reduction of O₂in the cathode reaction with Fe²⁺to produce strong oxidation of·OH for removing organic pollutants,Possesses the fast degradation rate,high efficiency,and can reduce the consume of Fenton reagent and so on.However,it exists a large kinetic energy barrier for O₂reduction to H₂O₂at cathode,which affects the degradation efficiency of electro-Fenton.Therefore,constructing an efficient electro-Fenton cathode materials is the key to accelerating the O₂reduction reaction and increasing the yield of H₂O₂.Biomass porous carbon has received extensive attention in electrocatalytic reduction of O₂to produce H₂O₂due to its advantages such as low cost,high specific surface area and high stability.In this thesis,waste distiller’s grains were used as biomass precursors for synthesizing oxygen-doped porous carbon（OPC）by high temperature carbonization and acid immersion.Then the performance of OPC electrocatalytic reduction of O₂to produce H₂O₂was investigated,and when it was used as electro-Fenton cathode,the degradation of BPs by electro-Fenton was studied.Finally,the removal mechanism and possible degradation pathways of BPA were proposed.The specific experimental contents and conclusions are as follows:（1）OPC material was successfully prepared using distiller’s grains as biomass precursors.Scanning electron microscopy（SEM）and N₂adsorption-desorption exhibit that the prepared carbon material was porous morphology with micropores and mesopores,and the specific surface area was 1432 m²/g.X-ray photoelectron spectroscopy（XPS）and fourier transform infrared spectroscopy（FTIR）analysis show that the material contained C and O elements,with the O content of 19.41 wt%and was defined as oxygen-doped porous carbon（OPC）.C and O combine in the form of oxygen functional groups such as-COOH and C=O,which was reported as the active center of electrocatalytic oxygen reduction.（2）OPC shows good oxygen reduction activity with oxygen reduction peak potential and current density are-0.12～-0.26 V and 0.52～0.62 mA/cm²at pH=2～6respectively.When OPC was used for electrocatalytic reduction of O₂to produce H₂O₂,the maximum yield at pH=2,4,6 was 15.46 mmol/L,12.87 mmol/L and 13.17mmol/L respectively,and the current efficiency for H₂O₂production could reach 50%at-0.3 V～-0.7 V,pH=2～6.（3）When OPC material was used in electro-Fenton system,under the optimized conditions of-0.5 V,0.3 mM Fe²⁺and pH=4,the apparent kinetic constants of degradation of 20 mg/L BPA and BPS by electro-Fenton were 0.267 min^-1and 0.319min^-1,respectively.The possible intermediate products were identified by ultra-high-performance liquid chromatography-tandem quadrupole mass spectrometry（UPLC-MS/MS）.Based on this,the process of electro-Fenton removal of BPA was inferred to be hydroxylation,ketoneation,oxidation and benzene ring cleavage,and then further decomposed into small molecules.