| The serious surface water pollution and water shortage in China are the important problems facing our country.More and more sewage treatment plants require the main indicators of the discharged water to reach the surface levelⅤ.Therefore,it is a difficult problem to find an efficient and clean method to treat low concentration of nitrate nitrogen in sewage.Electrochemical method is recognized as a promising technology for the treatment of nitric acid pollution.No additional reducing agent is needed in the reactor and nitrate ions are reduced directly or indirectly by electrolysis reaction on the electrode surface in the electrochemical process.There is no secondary contamination of other metal ions in the effluent after the reaction.Compared with the physical chemical method,the electrochemical method can completely remove the target pollutants,rather than simply transfer or concentration;Compared with the biological denitrification method,the electrochemical method requires no additional carbon source and is less affected by low temperature.Electrochemical method also has the advantage of high safety,selectivity of products can be controlled according to reaction conditions,and energy consumption and other costs are low.Existing electrochemical denitrification technologies are mainly aimed at wastewater with high concentration of nitrate nitrogen,but few studies have been conducted on the process of low concentration of nitrate nitrogen,and further studies on the removal law and kinetics of nitrate nitrogen are needed.In sewage treatment field nitrate is difficult to remove the technical problem,this study constructed the titanium ruthenium plating iridium anode electrochemical reaction system,iron nitrate solution of cathode,respectively in the hybrid reactor,membrane reactor,flow under the dynamic research process of low concentration of nitrate nitrogen removal in sewage,to research the composition of gaseous product,The effects of reaction conditions such as current density,p H,stirring rate,electrolyte concentration,initial nitrate concentration and Na Cl concentration on the removal efficiency of nitrate were investigated,and the removal mechanism was also studied.The main conclusions of the paper:（1）The gaseous products of the electrochemical reduction of nitrate are mainly ammonia and nitrogen,and the content of nitrous oxide is lower than the detection limit of gas chromatograph.（2）When the current density is 1mA·cm-2,the p H is 7,the stirring rate is 300 r·min-1,the electrolyte concentration is 0.02g·L-1Na2SO4,and the nitrate nitrogen concentration is 15mg·L-1,the removal effect of nitrate is the best,and the concentration of NO3—after reaction is6.4mg·L-1.The removal rate was 57%and 43%of total nitrogen.The orthogonal experiment in the mixed reactor showed that the electrolyte concentration had the greatest effect on the degradation of nitrate nitrogen,and the initial concentration of nitrate had the least effect on the denitrification.（3）The membrane reactor effectively avoids the reoxidation of ammonia nitrogen in the reduction product,and promotes the continuous removal of nitrate,but the reaction time required to reduce to the same concentration is longer than that of the mixed reactor.When the initial nitrate concentration is 15mg·L-1,p H value is 7.0,and Na Cl concentration is 75mg·L-1,the nitrate removal rate is 67%and the total nitrogen removal rate is 52%.The orthogonal experiment in a diaphragm reactor showed that the initial concentration of nitrate had the greatest effect on the denitration,while the concentration of Na Cl had the least effect on the removal of nitrate nitrogen.（4）The nitrate removal rate and total nitrogen removal rate of dynamic flow nitrate wastewater treated by diaphragm reactor are both lower than those in static experiment.The higher the flow rate was,the worse the nitrate removal effect was,and the concentration of ammonia nitrogen was the same after 600min reaction.The higher the initial concentration of ammonium,the higher the removal rate of nitrate in a certain range,the higher the removal rate of ammonia nitrogen,adding appropriate amount of ammonia nitrogen in the experiment is conducive to the removal of total nitrogen. |
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