| Phenolic compounds are widely used as an important class of chemical raw material in industrial and agricultural production,causing huge amounts of wastewater containing phenol accordingly.Nitrophenol compounds,a model for phenolic compounds,resisting biodegradation and hardly being removed by conventional biological treatment technology,can be mineralized completely by advanced oxidation technology.In recent years,Fenton-like oxidation has attracted wide attention due to advantages such as the high efficiency,rapid reaction speed and no secondary pollution.With P-nitrophenol?PNP?selected as the target pollutant,the mechanism and path of PNP degradation in the Fenton-like reaction and the main influencing factors were systematically studied in this thesis.The main contents and conclusions are as follows:?1?FeS2 was prepared by hydrothermal method as a Fenton-like catalyst.The analysis results of SEM and X-ray diffraction showed that the diameter of the powder was close to 5microns,the surface was loose and porous,and the spatial structure is the regular octahedron,which corresponds to the crystal of pyrite evidently.?2?PNP can be rapidly oxidized in Fenton-like reaction system using FeS2 as catalyst.The degradation rate of PNP was up to 91.5%after 60 minutes reaction in the dark.Active species quenching experiments showed that the main active species in the reaction system were·OH and·O2-,and·OH played the major role.Qualitative detection of standard substances by liquid chromatography showed that PNP was completely mineralized on the basis of the attack of·OH onto the hydrogen atom and amino group on the benzene ring.?3?The theoretical band gap of pyrite is about 0.95ev,so pyrite could effectively absorb and utilize visible light.The study showed that the visible light had an assistant effect on the pyrite-catalyzed Fenton oxidation,the degradation rate of PNP could reach 99.5%after 60minutes reaction.The main active species were·OH and·O2-in the reaction system with visible light.?4?In order to efficiently address the issue of lifetime and source of hydrogen peroxide,this paper investigates the degradation of the PNP,employing visible-light-driven electro-Fenton methods,in which oxygen was pumped into graphite cathode.After 60minutes reaction,the degradation rate of PNP reached 98.1%.The main active species were·OH and·O2-in the reaction system under visible light.As the main active species,the·OH radical firstly attacks C-C bond to form active biphenyl compounds,which further reacts with the·O2-radical to generate intermediates including p-nitrophenol and hydroquinone whose subsequent oxidization produces hydroxyquinol and pyrogallol followed by being completely oxidized.Three systems proposed in this paper could effectively treat wastewaters polluted by PNP,and visible light had a significant effect on Fenton-like reaction. |
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