Preparation of Fe-based Fenton-like Catalysts and Their Degradation Performance of Phenol

Author:Xia Zuo Xing

Supervisor:jiang zhao hua yao zhong ping

Database:Doctor

Degree Year:2019

Download:256

Pages:151

Size:9809K

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Owing to the stable structure of benzene ring in phenolic compounds,it is difficult to effectively degrade phenolic pollutions by common water purification techniques.As one of advanced oxidation techniques,Fenton-like technique with many characteristics including easy operation,mild processing conditions,controllability and strong oxidation activity,is suitable for handling wastewater containing phenolic compounds.However,when used in practical applications,there are several defects such as low activity under neutral condition and unacceptable recycle performance challenging previous Fenton-like catalysts.Furthermore,the structures of almost Fenton-like catalysts are nano particles,which are easy to agglomerate and difficult to be reused.Therefore,how to develop a Fenton-like catalyst with easy preparation,high catalytic activity,wide working pH range and good dispersibility become one of the significant targets in water treatment.The zero valence iron(ZVI)with the hierarchical dendritic structure was obtained by electrodeposition technique.The trunk and branch of dendritic ZVI were micron scale and nano scale,respectively,and the SBET was 41 m2/g.Phenol degradation experiments were employed to evaluate the catalytic capacity of samples.The Fenton-like catalytic capacity of ZVI was excellent to remove the phenol pollutions,but the passivation layer was easily formed on the ZVI surface,which decreased the stability of ZVI.By regulating the composition of electrolyte,Fe-Cu alloys were obtained,and the performances of catalytic activity and stability were improved in the comparisons with ZVI.There were two kinds of Cu atoms in Fe-Cu alloy:copper impurity atoms in Fe crystal and independent Cu phase.Cu components could promote the cycle of≡Fe3+and≡Fe2+and inhibit the surface passivation of catalyst.Under the conditions of pH 4.0,0.1g catalyst dosage and 6 mmol/L H2O2,the as-obtained Fe-25Cu could be utilized for 10times successively,and the removal efficiency of phenol in each run reached>95%.However,the dendritic ZVI and Fe-Cu alloy were inactive at neutral pH.The amorphous carbon-coated Fe@Fe3O4 materials and Fe-Cu@Fe3O4 materials were prepared by the combined methods of electrodeposition and solvothermal process,and Fe3O4 contents were controlled by regulating the ratio of ethanol and water.The thermal decomposition of ethanol generated amorphous carbon with abundant polar C-groups on the surface of catalysts,which were beneficial to adsorb H2O2 and phenol molecules through polar attraction.In addition,the amorphous carbon on catalyst surface has a positive influence on the transform of≡Fe3+/≡Fe2+,which could endow the amorphous carbon-coated Fe@Fe3O4 with good catalytic activity and reusability.However,the sample still presents no activity at neutral pH.Furthermore,the carbon-coated Fe-Cu@Fe3O4 materials could be used to remove phenol effectively,and the degradation process include the Fe-Fenton reaction and the Cu-reaction:under acidic conditions,both of Fe-Fenton and Cu-Fenton reactions could proceed,and the Fe-Fenton reaction plays a dominant role in the degradation of phenol;at neutral condition,the Fe-Fenton reaction is extremely inhibited,while Cu-Fenton still functions as the only·OH resource to degrade the phenol pollution.However,the strong Cu ions leaching during the degradation process caused the serious decline of catalyst’s activity in recycle experiments.On the basis of electrodeposition/solvothermal methods,using glucose as the precursor of carbon quantum dots(CQDs),the CQDs coated Fe@Fe3O4 materials and Fe-Cu@Fe3O4 materials were prepared.CQDs possessed strong reducibility to cause the substitution of Fe3+by Fe2+in Fe3O4 frameworks around CQDs,which could induce oxygen vacancies(OVs)formed in Fe@Fe3O4 component.During the phenol degradation process,CQDs could promote the cycle of≡Fe3+/≡Fe2+and adsorb the polar reactants around active sites.OVs could decrease the activity energy of H2O2transforming into·OH by stretching and weakening the O-O bond in H2O2 molecules,and interact with H2O molecules to strength the Fenton-like reaction under neutral pH.The CQDs coated Fe@Fe3O4 materials obtained at 160℃(EG160)can remove 95%phenol at the conditions of 0.1 g/L catalyst dosage,pH 6.0 and 60 min,which is considered as the optimal catalyst among this research with high catalytic activity,good reusable stability,wide working pH range and small Fe leaching.Nonetheless,owing to the effect of Cu component,CQDs could not induce OVs on the Fe-Cu@Fe3O4 materials,of which Fenton-like catalytic capacity was much lower than that of EG160.