Study On Competitive Mechanisms Of PBER Collaboratively Oxidizes Ammonia Nitrogen And Organic Pollutants

At present,common industrial wastewater such as landfill leachate,coking wastewater,petrochemical wastewater,sludge digestion liquid,etc.,is difficult to effectively treat such wastewater due to high ammonia nitrogen,low carbon nitrogen ratio and poor biodegradability.Electrocatalytic oxidation technology is highly efficient and environmentally friendly,and has attracted much attention in the field of high concentration refractory organic wastewater treatment.However,most of the current research is on the treatment of a single pollutant,and there is no clear understanding of the treatment process of various pollutants in wastewater and their competitive relations.Therefore,this thesis hopes to study the competitive mechanisms between organic matter and ammonia nitrogen by simulating the mixed wastewater of phenol and ammonia nitrogen,and further verify the competition relationship between the two through landfill leachate.The main conclusions are as follows:(1)The analysis of the ultraviolet absorption spectra of phenol at different degradation times verified the degradation path of phenol.Phenol was firstly degraded into quinones,which were accumulated in the maximum concentration at 30 min,then quinones were degraded into small molecular organic acids,and finally carbon dioxide and water were further degraded.The introduction of chloride ions has less effect on the degradation of phenol than COD degradation,and the active chlorine after the oxidation of chloride ions is more inclined to oxidize organic matter after the opening of phenol ring.(2)The introduction of chloride ions can greatly improve the removal of ammonia nitrogen,and indirect oxidation can promote the degradation of ammonia nitrogen.The analysis of the degradation mechanism of ammonia nitrogen shows that hydroxyl radical has a weak oxidation ability to ammonia nitrogen.The main way of electrocatalytic oxidation of ammonia nitrogen is to oxidize chlorine ions to produce intermediate product active chlorine,which reacts with ammonia nitrogen to produce intermediate product,and break the chloro-hydrogen bond to form hydroxylamine through hydrolysis reaction,and then further react to form nitrogen.In the process of oxidation,a small amount of nitrate nitrogen will be produced,which can also produce nitrogen on the surface of the cathode plate,and finally achieve the removal of total nitrogen in the wastewater.(3)In the chlorine-free system,the system is more inclined to oxidize organic matter for the degradation of organic matter and ammonia nitrogen.In the chlorinecontaining system,the competitive degradation relationship between organic matter and ammonia nitrogen can be divided into three processes.At the early stage,the system prefers to oxidize the ring structure of phenol.With the progress of the reaction,the system will reach A critical reaction state,where the critical coefficient ψ=2.17g/A?h,and most of the ring structure of phenol will be destroyed.There are more chain organic pollutants,after the reaction critical state,between the chain organic matter and ammonia nitrogen,the system is more inclined to degrade ammonia nitrogen.(4)According to the electrochemical test results,the oxidation peak of the three electrolytes in the cyclic voltammetry curve is small at the high potential,while the characteristic current peak appears near 0.25V(with chlorine)and 0.3V(without chlorine).The comparison shows that the characteristic peak of ammonia nitrogen is more significant than that of phenol,indicating that the degradation effect of direct oxidation on ammonia nitrogen is small.Compared with the characteristic peak of single substrate electrolyte,The characteristic peak of the electrolyte mixed with the two substrates is the smallest,which indicates that the competition between ammonia nitrogen and phenol will be generated when other substances are introduced into a single substrate.When mixed substrate is introduced,the characteristic peak of ammonia nitrogen curve changes greatly,indicating that in the mixed system,the degradation effect of ammonia nitrogen is greater than that of phenol,and there is competition between ammonia nitrogen and phenol in electrocatalytic oxidation degradation.LSV curve shows that different electrolyte solutions will have an obvious peak current near 1.25V(vs.SCE).When there is only a single substrate in the electrolyte,the peak current is larger,indicating that the electrode has a strong current response,and the electrocatalytic oxidation degradation efficiency is high.When another substance is introduced into the single substrate,the peak current will decrease.The current response on the electrode was weakened,and the electrocatalytic oxidation activity was weakened,indicating that there was a degradation competition between ammonia nitrogen and phenol.The peak current in the chlorine-containing system was greater than that in the non-chlorine-containing system,indicating that the introduction of chloride ions could enhance the electrode response and improve the electrocatalytic oxidation efficiency.(5)The degradation of organic matter and ammonia nitrogen under 0.15L/h and0.3L/h conforms to the competitive mechanisms of organic matter and ammonia nitrogen in the chlorine-containing system.At 0.15L/h,the cyclic structure of organic matter in wastewater can be destroyed by the system in the early stage.With the progress of the reaction,the system enters the critical reaction state at 50 min,where the critical reaction coefficient ψ=2.10g/A·h,and most of the cyclic organic matter in wastewater is destroyed.Then the system is more inclined to degradation ammonia nitrogen between chain organic matter and ammonia nitrogen.After 150 min degradation,the COD removal rate reaches 49.98%,the energy consumption is0.036kwh/g COD,the ammonia nitrogen removal rate is 98.71%,the energy consumption is 0.054kwh/g ammonia nitrogen,and the carbon nitrogen ratio of effluent is 115.63.To meet the requirement of carbon nitrogen ratio in subsequent biological treatment.The critical reaction state was obtained by decreasing the solution for 75 min at 0.3L/h,and the critical reaction coefficient ψ=2.15g/A?h.In the experimental process,the degradation of organic matter and ammonia nitrogen still conforms to the competitio mechanism of the degradation of organic matter and ammonia nitrogen in the chlorocontaining system.The critical reaction state enters at 125 min,and the critical coefficient of the reaction is 2.22g/A?h,the removal rate of 240 min COD is 59.26%,and the energy consumption of the reactor is 0.031kwh/g COD.The removal rate of ammonia nitrogen reached 85.42%,and the energy consumption was 0.169kwh/g.The total power consumption is 47.4 degrees/ton.The effluent C/N ratio was 15.79,which could meet the requirement of C/N ratio for subsequent biological treatment.This thesis has 43 figures,7 tables and 125 references.