Carbonation Of Fe-tripyridine Compound To Activate Persulfate To Degrade Emerging Contaminants In Water

Industrial development has led to a rapid increase of emerging contaminants such as antibiotics and endocrine disruptors in water,which pose a serious threat to the ecological environment and human life and health.Advanced oxidation techniques such as Fenton/Fenton-like reactions are considered as a powerful technology for the removal of emerging contaminants due to their strong oxidative and non-selective properties.However,the application of this technology is still limited by its inherent bottlenecks,such as low activity due to the existence of a rate-limiting step in electromigration conversion,high cost due to the consumption of large amounts of strong oxidants,and the generation of solid hazardous waste from the reaction process.In recent years,Fenton-like technologies based on peroxynitrite(PMS)activation have shown better activity for emerging contaminants removal,especially the development of solid-phase catalysts containing transition metals,which have solved the problems of classical Fenton reactions such as hazardous waste generation to some extent.However,the problems of catalyst activity,stability and large amount of oxidant consumption still exist.Accordingly,this paper addresses the scientific problem of electron migration conversion limitation at the activation interface of PMS by carbonizing Fe-tripyridine compounds and precisely constructing Fe-N coordination structures on the material surface to induce metal cation-π interactions to achieve efficient activation of PMS and rapid removal of pollutants with simultaneous reduction of oxidant consumption.Two main aspects of the work include the following:First,supramolecular precursors with single-molecule Fe-N structures were obtained by a stepwise synthesis method,followed by surface modification through a carbonization process to obtain a new carbon-based Fe-N coordination catalyst FDV-550.The formation of Fe-N structures was demonstrated using techniques such as electrospray ionization mass spectrometry and nuclear magnetic resonance.The Fe-like graphene structure formed after carbonization was revealed by scanning electron microscopy(SEM),transmission electron microscopy(TEM),X-ray diffraction(XRD),X-ray photoelectron spectroscopy(XPS)and Fourier infrared spectroscopy(FTIR).The activity evaluation revealed that the antibiotic contaminants tetracycline and ciprofloxacin were completely degraded within 5 min in the FDV-550/PMS system,and the degradation rate of the nicotine insecticide imidacloprid,which contains a refractory pyridine conformation,exceeded 30%,reflecting the excellent performance of Fe-N conformation for PMS activation and contaminant degradation.On this basis,the effects of PMS and FDV-550 concentrations on the degradation efficiency of antibiotic contaminants were investigated in depth,and the degradation intermediates of contaminants were analyzed by triple tandem quadrupole liquid mass spectrometer(LC-MS),and the contaminant degradation pathways were proposed.The main reactive oxygen species generated during the reaction were detected using EPR and other techniques to verify the mechanism of oxidative degradation of pollutants by hydroxyl radicals.The above work confirmed the feasibility of constructing new carbon-based Fe-N coordination catalysts by carbonizing single-molecule Fe-tripyridine compounds,and the formation of Fe-N conformation was beneficial to the efficient activation of PMS and rapid degradation of pollutants.In order to further enhance the activation of PMS and increase the removal efficiency of the emerging contaminants,a multimolecular Fe-N coordination catalyst FTA-550 was successfully constructed by carbonizing the catalyst precursor in the form of a mixture based on the above work,and the formation of Fe-N conformation was also confirmed by the above characterization technique.The activity evaluation revealed that not only the antibiotic contaminants tetracycline and ciprofloxacin could be removed rapidly in the FTA-550/PMS system,but also the degradation rate of the nicotine insecticide imidacloprid was significantly increased to more than 90%,reflecting the enhanced effect of the multimolecular Fe-N conformation on the activation of PMS and the removal of difficult to degrade emerging contaminants.On this basis,the effects of PMS and FTA-550 concentrations on the degradation efficiency of antibiotic contaminants were further investigated,and the degradation intermediates of contaminants were analyzed by LC-MS to propose the contaminant degradation pathways.In this study,it was found that through the construction and enhancement of Fe-N on the material surface,the reaction system can rapidly remove the hard-to-degrade emerging contaminants in water under the conditions of low concentration of PMS(1 m M-2 m M),and significantly reduce the energy consumption of water treatment resources,which can help solve the problems of high energy consumption and high concentration of sulfate ion generation in the practical application of PMS activation technology.