Preparation And Electrocatalytic Performance Of V₂O₅/Ti Composite Electrode Membrane For Ammonia Nitrogen Removal

Ammonia nitrogen wastewater is the most common inorganic wastewater with wide sources.In this paper,the electrocatalytic membrane reactor（ECMR）was assembled with V₂O₅/Ti composite electrode membrane as anode and stainless steel network as cathode for the treatment of ammonia nitrogen wastewater.V₂O₅/Ti were prepared by sol-gel method and magnetron sputtering,respectively.The structure and properties of the prepared electrode were characterized by X-ray diffraction,X-ray photoelectron spectroscopy,Field emission scanning electron microscopy and Electrochemical workstation.V₂O₅catalytic layer was coated on Ti substrate by sol-gel method,and the effects of different thermal annealing temperature（300°C,400°C,500°C）on the structure and electrochemical properties of V₂O₅/Ti（VT-300,VT-400,VT-500）were investigated.The results showed that with the increase of thermal annealing temperature from 300°C to 500°C,the crystallization degree of V₂O₅ in composite electrode membrane gradually increased,and the grain size increased from 15 nm to22 nm.The XPS results showed that after V₂O₅ loading on the Ti substrate,V peaks（0.1 e V）shift to higher values and Ti peaks（1.1 e V）shift to lower values,indicating changes in the surface electronic state of V and Ti elements and the formation of new Ti-O-V bond.The results showed that VT-500 had a larger electrochemical active area of 1.68 cm² compared with the other two composite electrode membrane,and better electrochemical performance.ECMR was assembled with VT-500 as anode to treat ammonia nitrogen wastewater.The operating conditions were as follows:the initial concentration of simulated ammonia nitrogen wastewater was 60.4 mg/L,the residence time was 8 min,the current density was 0.4 m A/cm²,p H was 7.0,and the temperature was 30℃.The ammonia nitrogen removal rate of ECMR reached 65.9%.V₂O₅/Ti composite electrode membrane was prepared by magnetron sputtering with V₂O₅ target sputtering on Ti substrate.The effect of sputtering temperature（150°C,300°C,450°C）on the structure and properties of V₂O₅/Ti composite electrode membrane was studied.The results showed that the V₂O₅/Ti composite electrode membrane prepared at a sputtering temperature of 300°C had a larger electrochemical active area,a smaller interfacial charge transfer impedance and larger diffusion coefficient,showing a strong electrochemical activity.ECMR was assembled with V₂O₅/Ti prepared at a sputtering temperature of 300°C as anode to treat ammonia nitrogen wastewater.The operating conditions in the reactor were as follows:the initial concentration of simulated ammonia nitrogen wastewater was 60.4mg/L,residence time was 8 min,current density was 0.4 m A/cm²,p H was 7.0,and the ammonia nitrogen removal rate reached 52.18%.ECMR assembled with VT-500 as anode and stainless steel as cathode to treat ammonia nitrogen wastewater.The effects of different ECMR process parameters（current density,residence time,p H）on the efficiency of electrocatalytic membrane reactor were investigated,and the response surface methodology was carried out to optimize the operating process parameters.The results showed that the current density had the greatest influence on the effect of ECMR in ammonia nitrogen treatment.The results of response surface method indicated that the significance of operating parameters for ammonia nitrogen removal rate is:current density>p H>residence time.Under the optimal operating conditions:experimental temperature was 30℃,current density was 0.85 m A/cm²,residence time was 9.80 min,p H was 7.82,operating voltage was 2.0 V,electrolyte（Na Cl）concentration was 18 g/L,initial concentration of electrocatalytic treatment was 60.4 mg/L,and the ammonia nitrogen removal rate was up to 93.96%.The ammonia nitrogen degradation rate only decreased 2.17%after 10 times of continuous electrocatalysis of ammonia nitrogen wastewater,which proved that the V₂O₅/Ti electrode was quite stable in the ammonia nitrogen treatment process.