Ammonia Oxidation Based On Bicarbonate Reduction Under Electric Field Negative Entropy Inpu

As one of the main pollutants in water,ammonia nitrogen will not only cause ecological environmental effects such as eutrophication,but also threaten human health,and HCO₃^-,as an existing form of CO₂in water,is also one of the components of water alkalinity.Realizing the synergistic removal effect of ammonia nitrogen and HCO₃^-,is of research significance to expand the new way of nitrogen and carbon cycle.In this paper,through the construction of a two-chamber electrically assisted microbial reactor,the idea of coupling anodic direct ammonia oxidation with cathodic functional microbial reduction of bicarbonate under negative entropy（external electric energy）input is proposed for the first time.Bicarbonate reduction-ammoxidation reaction was successfully initiated（Gibbs free energyΔG>0,which could not be spontaneous under natural conditions）.On the one hand,the ammonia pollution in water is reduced,on the other hand,HCO₃^-（CO₂）is converted into energy product,and the recycling of CO₂is realized,and a new way of N and C cycle is obtained.In this paper,the functional microorganisms producing acetic acid were cultured and domesticated by electrically assisted microbial reactor.The Ti/Ir O₂-Ta₂O₅electrode and composite electrode composed of Fe₃O₄modified carbon felt filled with Na⁺modified zeolite designed and constructed in this paper were used as the anodes of the two-chamber reactor to start the bicarbonate reduction-ammoxidation reaction in alkaline and neutral anodic electrolytes.The starting conditions and degradation effect of coupling reaction were analyzed according to the influence factors of coupling reaction,degradation mechanism,electrode materials,reaction substrates and products.Combined with molecular biology technology,the reaction mechanism of synergism between electrochemistry and functional microorganisms was explored.The main conclusions are as follows:（1）The strain with the function of reducing HCO₃^--C to acetic acid was successfully screened by using the applied voltage electron donor in the two-chamber electrical auxiliary system,and the bacteria such as Clostridium,Sporomusa and Geobacter with the function of electron transfer and extracellular electron transfer were detected at the subordinate level.At the end of domestication,the conversion rate of sodium bicarbonate was about 78%,and an obvious reduction peak was observed on the cyclic voltammetry curve of the biofilm electrode.（2）Bicarbonate reduction-ammoxidation reaction was realized in alkaline anodic electrolysis environment when Ti/Ir O₂-Ta₂O₅was used as the anode material of two-chamber electrically assisted microbial reactor.Among them,the coupling degradation effect of anodic solution p H=10 and applied electric potential was 1.5 V is the best,the degradation rate of ammonia nitrogen and HCO₃^--C of the reaction system is 78.9%and 64.6%respectively,and the amount of acetic acid produced by cathode is 32.28±1.51 mg/L,while the non-biological control group and non-potential control group could not achieve the coupling degradation of NH₄⁺-N and HCO₃^--C.（3）In order to overcome the deficiency of ammonia nitrogen in alkaline anodic electrolysis,a composite electrode composed of Fe₃O₄modified carbon felt filled with Na⁺modified zeolite was designed and used as the anode plate of two-chamber electrically assisted microbial reactor to successfully realize bicarbonate reduction-ammoxidation under neutral anodic electrolysis conditions.Under the appropriate carbon felt thickness,the reaction system realized the coupling reaction of anodizing NH₄⁺-N and cathodic functional microorganism reducing HCO₃^--C to acetic acid.The degradation rate of NH₄⁺-N and HCO₃^--C reached 84.2%and 47.4%respectively within 20 hours when the applied potential of the system was 1.5V,and the accumulation of cathodic acetic acid reached 21.98 mg/L at the end of the reaction.