Preparation Of Co/AC_0.9-AB_0.1 Catalytic Particle Electrode And Application In Deep Denitrification Of Sewage Tail-water

After the aerobic biological treatment,the nitrogen?N?in the tail-water of municipal sewage is mainly composed of nitrate-N and a small amount of ammonia-N.The nitrate will cause many adverse effects on water environment and human health.Two-dimensional?2D?electrochemical denitrification technology has the characteristics of environmental protection and easy operation.So,it is considered as the most potential denitrification technology.However,the 2D electrochemical denitrification technology has a low denitrification efficiency due to the lack of active sites.Morever,because of the low electrolyte concentration and poor electrical conductivity in sewage tail-water,the problem of high energy consumption of denitrification is brought about.Therefore,this paper prepared a catalytic particle electrode?Co/AC_x-AB_y?for deep denitrification of sewage tail-water.Activated carbon?AC?was used as the carrier material of the metal catalyst,acetylene black?AB?was used as the conductor,and cobalt?Co?was used as the catalyst.The proposed catalytic particle electrodes were applied in a continuous three-dimensional?3D?electrochemical reactor.Based upon the removal efficiency of total nitrogen?TN?,plate voltage,and the corresponding energy consumption,the optimum mass ratio of AC to AB was determined to be 0.9:0.1.The Co/AC_0.9-AB_0.1 catalytic particle electrode was characterized by Brunner-emmet-teller?BET?,Malvern laser particle size,Scanning electron microscopy?SEM?,X-ray diffraction?XRD?,and X-ray photoelectron spectroscopy?XPS?.Compared with AC,the specific surface area and total pore volume of Co/AC_0.9-AB_0.1 catalytic particle electrode decreased to some extent,while the average pore diameter increased slightly,from 3.290 to 3.429 nm.The particle size of AC is 19?m,which is smaller than the particle size of AB?50?m?.SEM and energy dispersive system?EDS?-mapping analysis showed that white crystal particles were distributed on the surface of Co/AC_0.9-AB_0.1.XRD and XPS analysis results showed that Co/AC_0.9-AB_0.1 contained three valence states of Co,namely Co⁰,Co²⁺,and Co³⁺.Additionally,batch experiments showed that 95%of TN removal was achieved under the current of 0.4 A,p H of 7,hydraulic retention time?HRT?of 60 min,and the initial concentration TN of 20 mg/L.The addition of Cl^-was obviously beneficial to the removal of TN,because Cl O^-from Cl^-electro-oxidation can react with ammonia,whereas HCO₃^-,PO₄^3-,CO₃^2-,and dissolved organic matter?DOM?inhibited the removal of TN.The denitrification experimental results of Co/AC_0.9-AB_0.1 catalytic particle electrode in practical sewage tail-water show that the removal efficiency of nitrate can be maintained at 90%.It was found that Co/AC_0.9-AB_0.1 catalytic particle electrode had the maximum current density of hydrogen evolution under neutral conditions.The Tafel slope of Co/AC_0.9-AB_0.1 catalytic particle electrode was about 120 mv/dec under acidic or neutral,indicating that the adsorbed hydrogen was formed on Co/AC_0.9-AB_0.1 catalytic particle electrode.By measuring the cyclic voltammetry?CV?curve of the non-faraday region,the double-layer capacitance(C_DL)?10.9 m F/cm²?and the maximum electrochemical active surface area?ECSA??3.75 m²/g?of Co/AC_0.9-AB_0.1 under neutral can be obtained.By testing the CV curve of nitrate,no obvious redox peak was observed,indicating that the nitrate did not directly reduced by obtain electrons from the cathode.However,the detection of hydrogen radical?H·?by electron spin resonance?ESR?indicates that nitrate was removed by indirect reduction of H·.