| With the rapid development of China’s economy and society,large amounts of nitrogen and phosphorus wastewater are discharged into the water body.As a result,nearly half of surface water and groundwater are facing different degrees of eutrophication.Because of low cost,high treatment efficiency and simple operation,Iron-carbon micro-electrolysis technology is popular to treat nitrogen and phosphorus wastewater.Its main principle to remove pollutants in water is to produce a large number of electrons and highly reactive substances through the formation of primary cell electrode reaction based on the corrosion of metal materials.The performance of fillers is the key factor affecting the treatment effect.Most of the traditional iron-carbon micro-electrolysis fillers are directly made of large-size iron carbon blocks or powders,or bonded by adhesives（such as bentonite）.The former often has the problems of low treatment efficiency and easy passivation in wastewater treatment,and hardening and blocking easily appear after long-term operation.The latter solves the problems of filler hardening and blocking to some certain extent,but the addition of adhesive reduces the proportion of functional components in the whole filler system and results in the low treatment efficiency.To solve the problems caused by large-size iron carbon materials and the addition of adhesive,it was proposed to prepare iron-carbon micro-electrolysis filler（Fe-K-CT type filler）by bonding carbon deposition sponge iron with functional adhesive kaolin to reduce the size of materials based carbon and integrate bipolar materials in micro-electrolysis by carbonization and deposition of the coal tar on the surface of sponge iron in oxygen free calcination,and exert the adhesive’s pollutant adsorption function.Firstly,the nitrogen and phosphorus removal function of kaolin and modified kaolin by calcination was clarified,and the ammonia nitrogen and TP were used as evaluation indexes.Based on the optimization of the preparation process,the nitrogen and phosphorus removal performance of Fe-K-CT,Fe|B|ACand Fe|K|AC fillers were compared,and the influencing factors of nitrogen and phosphorus removal effect of Fe-K-CT filler were discussed.The kinetic study provided support for the practical application of iron-carbon micro-electrolysis filler based on carbon deposition bonded by functional adhesive.The main conclusions are as follows:（1）The adsorption of ammonia-nitrogen and TP by kaolin and bentonite reached equilibrium state at 60 min.The removal rate of ammonia-nitrogen by kaolin was 9.06%,which was twice that of bentonite.The removal rate of TP by kaolin was 75.70%,which was much higher than that of bentonite（9.09%）.Bentonite had little ability to remove ammonia-nitrogen and phosphorus.（2）With the increase of calcination temperature,the removal rate of ammonia-nitrogen and TP by kaolin increased first and then decreased.When the calcination temperature was 600℃,the removal rates of ammonia-nitrogen and TP by kaolin were the highest,reaching 20.29%and 98.34%respectively.（3）The optimum preparation conditions of Fe|B|AC type filler were as follows:iron carbon mass ratio 1:1,bentonite mass fraction 30%,calcination temperature 900℃,calcination time 60min.The optimum preparation conditions of Fe|K|AC type filler were as follows:iron carbon mass ratio 1:1,kaolin mass fraction 30%,calcination temperature800℃,calcination time 60min;The optimum preparation conditions of Fe-K-CT type filler were as follows:iron coal tar mass ratio 3:1,the constant temperature of carbon deposition 900℃,constant temperature time 30min,kaolin mass fraction 30%,calcination temperature 900℃,and calcination time 60min.（4）Compared with Fe|B|AC and Fe|K|AC type fillers,Fe-K-CT type fillers showed greater advantages in ammonia-nitrogen and phosphorus removal,especially it could meet the standard discharge of TP within 30 minutes（the first level A standard of“Discharge Standard of Pollutants for Urban Sewage Treatment Plants”（GB18918-2002））.（5）In the carbon deposition stage of preparing Fe-K-CT filler,not only the carbon particles were deposited on the surface and internal pores of sponge iron,but also the reduction of Fe3O4 in sponge iron was promoted;the performance of carbon deposition iron material to remove ammonia-nitrogen and phosphorus reached optimal level when the C/Fe0 ratio was about 0.062.（6）The effects of initial pH,aeration rate and solid-liquid ratio on nitrogen and phosphorus removal were significant.Increasing the initial pH of wastewater,aeration rate and solid-liquid ratio were beneficial to the removal of ammonia-nitrogen;decreasing the initial pH,increasing the aeration rate and solid-liquid ratio were beneficial to the removal of TP.（7）Fe-K-CT type filler could remove TP more effectively than ammonia-nitrogen.Under the optimal operating conditions of initial pH=7,solid-liquid ratio of 1:10,aeration rate of 60 ml/min,and reaction time of 30min,the residual concentration of TP was 0.14mg/l,and the removal rate was 97.66%,which had met the the first level A standard of“Discharge Standard of Pollutants for Urban Sewage Treatment Plants”（GB18918-2002）,while the residual concentration of ammonia nitrogen was 24.99mg/l,and the removal rate was 28.60%.（8）Under the optimal operating conditions,the performance of ammonia-nitrogen and phosphorus removal of the fillers was ranked as Fe-K-CT>Fe|K|AC>Fe|B|AC.At the same reaction time,the removal rate of TP by Fe|K|AC was almost 1.5～4.5 times of that by Fe|B|AC,and the removal rate of TP by Fe-K-CT was 3.5～8 times of that by Fe|K|AC.（9）The removal of ammonia-nitrogen by iron-carbon micro-electrolysis basically conformed to the third-order kinetics model,the kinetic equation of fitting curve was y=7.132×10-6x+6.709×10-5（R2=0.91033）,and the reaction rate constant was 7.132×10-6;the removal of TP by iron-carbon micro-electrolysis basically conformed to the first-order kinetics model,the kinetic equation of fitting curve was y=0.07588x+0.49531（R2=0.95351）,and the reaction rate constant was 0.07588. |
