Preparation Of Fe-Co-Bi/Kaolin Particle Electrode And Degradation Of Quinoline By Electro-Fenton System

Quinoline is a kind of typical nitrogen-containing heterocyclic compounds,and widely exists in various industrial organic wastewater.Quinoline and its derivatives have the characteristics of stable structure,high toxicity and difficult biodegradation.Conventional wastewater treatment methods such as physicochemical and biological methods are difficult to degrade quinoline.Electro-Fenton advanced oxidation process,as an efficient and environmentally friendly wastewater treatment method,has unique advantages in the field of wastewater treatment.At present,there are few reports on the degradation mechanism and pathway of quinoline by electro-Fenton process,so it is of great significance to study the degradation of quinoline by electro-Fenton process.Quinoline was taken as target pollutant.Two-dimensional electro-Fenton process was used to degrade quinoline.The reaction conditions were optimized by single factor experiment,and COD degradation kinetics of quinoline solution was studied.Intermediates of quinoline were identified by gas chromatography-mass spectrometry(GC-MS),and possible degradation pathways were speculated.Fe-Co-Bi/kaolin particle electrode was prepared by solid-state calcination method with kaolin as carrier and FeCoBi composite metal oxide as active catalytic component.The preparation conditions of particle electrode were optimized,and its performance was tested by SEM,XRD,Py-IR,BET and resistivity meter.Particle electrodes were applied to the study of quinoline degradation by three-dimensional electro-Fenton process.The process conditions were optimized.The intermediates of quinoline degradation were identified by HPLC-MS,and pathways of quinoline degradation were speculated.It provided technical and theoretical support for degradation of quinolines by electro-Fenton process.The main research results are as follows:(1)In two-dimensional electro-Fenton process,sodium chloride was used as the supporting electrolyte.When initial pH value was 3.0,conductivity was 15800 μs/cm,H2O2 concentration was 71 mmol/L,current density was 30.5 mA/cm2,applied voltage was 26.5 V,and electrolysis time was 20 min,COD removal of quinoline solution could reach 75.56%.The COD decrease of quinoline solution followed first-order kinetic model.The main degradation products of quinoline were 2(1H)-quinolinone,4-chloro-2(1 H)-quinolinone,5-chloro-8-hydroxyquinoline and 5,7-dichloro-8-hydroxyquinoline.The possible pathways of quinoline degradation:under the attack of ·OH and active chlorines,quinoline molecules were hydroxylated and chlorinated to form hydroxylated derivatives or chlorinated derivatives.then derivatives were cleaved to form nitrogenous intermediates and aromatic compounds,which were further mineralized to CO2 and H2O.(2)The optimum preparation conditions of Fe-Co-Bi/kaolin particle electrode are as follows:material ratio(metal salt:kaolin,mass ratio)is 1:1,and calcination temperature is 800℃.SEM results showed surface of Fe-Co-Bi/particle electrode had larger roughness and more pores;XRD results showed Fe and Co loaded on kaolin formed composite metal oxide Co0.62Fe2.38O4,and Bi mainly existed in the form of Bi2O2.75;Py-IR results showed Fe-Co-Bi/kaolin particle electrode had more weak acid active sites,and its type was L-acid type;BET analysis results showed specific surface area of Fe-Co-Bio/kaolin particle electrode was 104.2750 m2/g,and it had macroporous structure;The resistivity test results showed resistivity of Fe-Co-Bi/kaolin particle electrode was 1.13×105Ω·cm,which was a semiconductor material with high impedance conductivity.(3)In three-dimensional electro-Fenton process,when particle electrode dosage was 40 g/L,initial pH value was 3.5,H2O2 concentration was 67.6 mmol/L,conductivity was 12670μs/cm,applied voltage was 20 V,and electrolysis time was 20 min,COD removal rate of quinoline solution could reach 88.68%.The main intermediates detected by HPLC-MS were 5-hydroxyquinoline,8-hydroxyquinoline,2(1 H)-quinolinone,2-formamidobenzoic,2-(2-aminophenyl)-2-oxoacetic acid,benzoic acid,etc.The possible pathways of quinoline degradation were as follows:2,5 and 8 positions of quinoline were attacked by ·OH to form hydroxylated derivatives,then benzene ring or pyridine ring was cracked to produce aldehydes,organic acids,which were mineralized into CO2 and H2O.