Study On Preparation And Electrochemical Properties Of Fly Ash Based Geopolymer Composite Anode

As an advanced oxidation processes,electro-catalytic oxidation has attracted more attention in the treatment of wastewater due to its high catalytic activity and less secondary pollution.The anode material is the core of this technology,which directly affects the degradation efficiency of wastewater.At present,the research on anode materials has made some progress at home and abroad,but there are still some problems such as high cost and poor stability.Therefore,the research and development of novel anode materials is extremely urgent.As a kind of catalyst,geopolymer is cheap and easy to prepare,but its poor conductivity limits its application in the electrocatalysis field.In view of this,we developed to prepare ?-Fe₂O₃/FAG composite anodes used dip-coating method with stainless steel sheet substrate coated with ?-Fe₂O₃ and fly ash based geopolymer(FAG).The composition,surface topography and electrochemical properties of the composite anodes with different ?-Fe₂O₃ loading were characterized,and the composite anodes were applied to the electrocatalytic degradation of dye wastewater.X-ray diffraction,scanning electron microscope and energy-dispersive X-ray spectrum results showed that ?-Fe₂O₃ was successfully loaded on the surface of FAG,and with the increase of ?-Fe₂O₃ loading to 10wt%,the surface of the composite anode became more uniform and compact.The linear sweep voltammetry,cyclic voltammetry and electrochemical impedance spectroscopy results showed that ?-Fe₂O₃/FAG composite electrode with 10wt% ?-Fe₂O₃ loading has higher oxygen evolution potential,larger electrochemical active area and lower interfacial resistance.The properties of electrocatalytic degradation of indigo carmine dye by ?-Fe₂O₃/FAG composite anodes were evaluated.The results showed that the electrocatalytic activity of ?-Fe₂O₃/CFAG composite anode was closely related to the loading appropriate amount of ?-Fe₂O₃.When the ?-Fe₂O₃ addition was 10wt%,the degradation efficiency of indigo carmine dye by 10 ?-Fe₂O₃/FAG composite anodes approached to 92.6%in 90 min,due to the generation of strong oxidative hydroxyl radicals.The composite anode had good stability,and the degradation rate of indigo carmine dye remained 83.5% after five cycles.The kinetic analysis showed that the degradation reaction accorded with the first order kinetics.The effects of the loading of ?-Fe₂O₃,voltage and dye concentration on the degradation rate of indigo carmine were investigated by response surface methodology.The main factors affecting the degradation rate of indigo carmine were as follows:the loading ?-Fe₂O₃>voltage>dye concentration.The optimum parameters for the degradation experiment were that the loading of ?-Fe₂O₃ was 12.78%,the voltage was0.79 V,the dye concentration was 13.15 mg/L,and the predicted degradation rate of indigo dye was 95.46%.The experimental values(94.70%)were in good agreement with the predicted values,which indicated that the regression model was reliable.In addition,the properties of electrocatalytic degradation of crystal violet dye and direct dark blue dye by ?-Fe₂O₃/FAG composite anodes were evaluated.The results showed that the degradation efficiency of 10 ?-Fe₂O₃/FAG composite anode for crystal violet dye was 45.4%in 100 min,and the degradation reaction was in accordance with the second order kinetics.The degradation efficiency of 10 ?-Fe₂O₃/FAG composite anode for direct dark blue dye was 70.0% in 40 min,and the degradation reaction was in accordance with the second order kinetics.