Mechanism Of Graphene-like Dual-electric-center Fenton-like Catalytic Degradation Of Organic Pollutants In Water

Industrial wastewater discharges are increasing annually,posing a serious threat to people's health and safety,so it is urgent to develop cost-effective and efficient technologies and methods to remove organic pollutants.Among the many advanced oxidation processes(AOPs),Fenton advanced oxidation was widely used to degrade refractory organic pollutants.However,the homogeneous Fenton reaction requires strongly acidic conditions(p H 2.0 to 3.5)and produces large amounts of iron sludge,which inhibits its application in wastewater treatment.To solve these problems,heterogeneous Fenton-like catalysts have received great attention.However,the catalytic mechanism of most heterogeneous catalysts is the redox reaction between the metal active components on the catalyst surface and H₂O₂ to the generation of free radicals for pollutants degradation,which results in the ineffective oxidation of excess H₂O₂ to O₂ and poor catalytic activity under neutral conditions.In this thesis,to address these existing problems of heterogeneous Fenton-like catalysts,a series of Fenton-like catalysts with dual-electric centers were developed by the construction of microelectric fields on the catalyst surface.The formation of dual-electric centers was confirmed by characterizations,including X-ray diffraction(XRD),X-ray photoelectron spectroscopy(XPS),X-ray absorption fine structure(EXAFS)and density functional theory(DFT)calculations,and the mechanism of pollutant degradation in water was explored.The main research contents and conculsions are as follows:(1)Graphene-like complexed copper oxide dual-electron-center Fenton-like catalysts(Cu-GCD NSs)were prepared.The formation of Cu-O-C chemical complexes between the Cu species on Cu-GCD NSs and the hydroxyl groups in the graphene-like substrate was confirmed by a series of characterizations,which induced the formation of surface electron-poor/rich centers(dual-electron centers).Cu-GCD NSs showed good catalytic activity,stability,and high hydrogen peroxide utilization for the degradation of aromatic organic pollutants such as BPA,IBU,DP,and PHT.And the interfacial interactions between the catalyst and organic pollutants,dissolved oxygen(DO),and H₂O₂ were probed by in situ Raman,electron paramagnetic resonance(EPR),and DFT,revealing that the electron-donor pollutants could be oxidized and decomposed in the electron-poor centers,while DO and H₂O₂ preferred to reduce in the electron-rich centers and reduced the ineffective oxidative decomposition of H₂O₂.This study showed that the electrons of pollutants can be effectively utilized in the Fenton-like reaction through the microelectric field on the catalyst surface,which provided an effective strategy to improve the Fenton-like reaction activity and reduce the H₂O₂ consumption.(2)Nitrogen-doped graphene-like complexed copper oxide dual-electron-center Fenton-like catalyst(Cu NC/PAN-3)was prepared.The formation of Cu-N-C and C-O-Cu bond bridges on the catalyst surface induced the formation of electron-rich centers around the copper species on the catalyst surface and the nitrogen-doped graphene-like structure with electron-poor centers.It is confirmed that organic pollutants as electron donors provide electrons in the electron-poor centers of nitrogen-doped graphene-like species to be decomposed by oxidation,and H₂O₂ and DO gains these electrons in the electron-rich centers of Cu species,and the nitrogen-doped graphene-like species enhances electron transport at the interface,resulting in more active species.Cu NC/PAN-3 shows efficient Fenton catalytic activity for most organic pollutants such as pesticides and pharmaceuticals with very low H₂O₂ consumption.(3)Nitrogen-doped graphene-like complexed copper oxide-coated zero-valent copper(Cu⁰@Cu O_x-NC)H₂O₂-assisted surface-limited Fenton-like catalysts were prepared.Cu-N-C and Cu-O-C chemical coordination bonds were formed between the Cu species and nitrogen-doped graphene-like,resulting in the formation of electron-rich centers around the Cu species and electron-poor centers around the nitrogen-doped graphene-like on the catalyst surface.This catalyst showed efficient Fenton catalytic activity for most organic pollutants such as pesticides and pharmaceuticals in water,and the reaction rate was no longer dependent on the increase of H₂O₂ concentration at H₂O₂ concentrations greater than 2 m M.Experiments and theoretical calculations showed that organic pollutants and intermediates,hydroxide(OH?)were restricted in the electron-poor centers to provide electrons,while O₂,H₂O₂,O₂^·-and^·OH were restricted in the electron-rich centers to gain electrons,and H₂O₂ is only used as one of the electron acceptors,so the consumption of H₂O₂ is reduced and the purification efficiency.(4)H₂O₂ triggered nitrogen-doped graphene-like complexation of bimetallic multivalent oxides with a dual-electron-center Fenton-like catalyst(Cu/Fe-N-C)was prepared.M-N-C and M-O-C chemical bond bridges were found to form between the metal species on Cu/Fe-N-C and the graphene-like substrate,resulting in the formation of electron-rich centers around the metal species and electron-poor centers around the graphene-like substrate.The catalysts can degrade organic pollutants such as BPA,CIP,PHT,IBU and DP rapidly within seconds at neutral conditions.It is confirmed that organic pollutants and OH?were restricted in the electron-poor centers to provide electrons,and O₂ and H₂O₂ were restricted in the electron-rich centers to gain electrons,driving electron transfer in the electron-poor/rich centers and polarizing the surface charge distribution,which in turn triggers efficient oxidative decomposition of organic pollutants on the catalyst surface.