Study On The Denitrification Regulation CharACFteristic By A Functional Electropolymerization Biocarrier Modified By Redox Mediator

With the fast development of modem industry and agriculture,inorganic nitrogen compounds have become common contaminates in surface water and groundwater in recent years.Biological denitrification is the most common technology employed for nitrogen removal in wastewater treatment.Some studies have been conducted to explore the catalytic effects of different redox mediators on the bio-transformation processes.But continuous dosing implies continuous consumption of soluble redox mediator as well as continuous discharge of biologically recalcitrant compounds.The aim of this study was to explore a new denitrification technology with functional electropolymerization biocarriers,which were prepared by the electropolymerization of polypyrrole(PPy)monomer on an active carbon felt(ACF)electrode with doping anions of redox mediator or Na2SO4.The ACFcelerating mechanism of the redox mediator was explained and analyzed for ORP and electron transport.This experiment selected five dissolved quinone mediators as redox mediator:anthraquinone-1-sulfonate(a-AQS),anthraquinone-2-sulfonate(AQS),anthraquinone-1,5-disulfonate(1,5-AQDS),anthraquinone-2,6-disulfonate(2,6-AQDS),anthraquinone-2,7-disulfonate(2,7-AQDS).In this experiment,functional electropolymerization biocarriers were prepared by the cyclic voltammetry electropolymerization of polypyrrole(PPy)monomer on an active carbon felt(ACF)electrode with doping anions of redox mediator or Na2S04.investigate the affecting factors of the denitrification process with redox mediator was investigated,which included the volume of AQS,carbon source,the ratio of carbon to nitrogen,temperature,pH,concentration of nitrite and oxidation reduction potential.In addition,the biological catalytic activity and durability were also tested by repeated-batch operations.The results were as followings:The optimum polymerization conditions determined by experiment were:polymerization potential was 0.95?1.15V,polymerization time was 3h,polymerization pH was 3.The denitrification rate was enhanced about 38%compared to the control.The characteristics of the electropolymerization biocarriers were analyzed by scanning electron microscope,elemental analyses,fourier transform infrared(FTIR)spectroscopy and raman spectroscopy.The results were as follows:AQS was dopinged with keepping quinone structure,the doping degree was 4.60:1,the volume of AQS dopinged in active carbon felt was 0.0428mmol.The suitalbe conditions of action were:the volume of AQS inputted was 0.1712mmol,carbon source was Sodium succinate,the ratio of carbon to nitrogen was 6:1,temperature was 35?,pH was raised,the denitrification rate was acceleraed and the accumulation of nitrite was reduced,the oxidation reduction potential and reaction energy were decreased.Then Repeated-batch operations indicated that the denitrification efficiency with redox mediator was enhanced 35%and exhibited better catalytic ACFtivity and durability.Five dissolved quinones accelerated the biological denitrification efficiency,the accelerating efficiency order was:AQS,2,7-AQDS,2,6-AQDS,?-AQS,and 1,5-AQDS.The oxidation reduction potential of five dissolved quinones was lower than that of the control,and the order was opposite to the denitrification rate.By analyzing the ?E,E0' and| ip,a/ip,c |,The quinones compound accelerated biological denitrification efficiency because the reduction potential was low to nitrate,and the acceleration effect is more apparent because of E0' and | ip,a/ip,c |.Based on the above results,it was concluded that the electropolymerization-doping technology is an suitable method,it enhanced the biological denitrification rate,and slove the problem of secondly pollution.It provided a new idea for improving the biological denitrification rate.Therefore,it has great potential application for accelerating biological denitrification efficiency.