| The damage caused by nitrogen oxides（NOx）to the atmosphere has become an important factor affecting the ecological environment and sustainable socio-economic development,for which China has set strict NOx emission standards.Industry the main source of NOx in flue gas of coal-fired power plant boiler,and a variety of small and medium-sized industrial kiln industry,in order to control industrial,NOx in flue gas can be used dry denitrification technology and wet denitrification technology two ways.Wet denitrification process in the oxidation process of mild operating conditions,low equipment investment,easy to achieve the collaborative removal of pollutants such as SO2,may be in the form of nitrate recycling NOx in the flue gas,the process is more green environmental protection,is an important direction of denitrification technology development,but the characteristics of NO insoluble in water restricts the development of its industrial application in flue gas treatment.Therefore,the search for efficient,economical and environmentally friendly liquid phase oxidation method and oxidizer has become the key to the development and application of wet denitrification technology.Advanced oxidation technologies（AOPs）based on activated persulfate,which can efficiently and rapidly oxidize insoluble NO to water-soluble NO2by generating strong oxidizing radicals through thermal,ultrasonic,optical,electrical and transition metal activation,thereby increasing the mass transfer driving force to accelerate the dissolution of NO.Transition metal iron is widely used as an efficient activator of persulfate due to its low price and non-toxic properties.In homogeneous activation systems,Fe2+is rapidly converted to Fe3+,resulting in a decrease in the concentration of Fe2+in the system,leading to a reduction in the activation effect.To improve the utilization of Fe2+,this paper adopts the method of chelating Fe2+with citric acid（CA）to activate the oxidation absorption of NO in simulated flue gas by（NH4）2S2O8.A bubble reactor is used as the reaction device to explore the feasibility of the technique.The reaction process of wet NO removal in the system is clarified through analysis and characterization methods.To further improve the effect of NO removal by persulfate purification in simulated flue gas,a super-heavy rotation packing bed is used as the reaction device to explore the wet denitrification process of persulfate.The effect of（NH4）2S2O8concentration,Fe2+concentration,CA/Fe2+molar ratio,temperature and p H of the absorbent and NO concentration on the NO purification was investigated using a bubbling reactor as the absorption device,（NH4）2S2O8solution as the absorbent and NO and N2mixture as the simulated flue gas.The results of the orthogonal tests showed that the influence of each factor on the purification rate was in the following order:temperature>p H>c（（NH4）2S2O8）>c（CA）>c(Fe2+).Single-factor experiments showed that increasing the concentration of（NH4）2S2O8and the temperature of the absorbent solution as well as adding an appropriate amount of CA would promote the purification effect of the reaction system for NO;increasing the p H of the solution and increasing the concentration of NO would have a negative effect on the purification of NO;the suitable operating parameters were determined as follows:c（NO）of 550ppm,c（（NH4）2S2O8）of0.2mol·L-1,c(Fe2+)of 0.01mol·L-1,c（CA）:c(Fe2+)of 1:1,p H of about 3 and T of 70°C.Under these conditions,the purification rate of NO could reach about 71.1%.The trend of Fe2+concentration over time was measured spectrophotometrically,and the results showed that the Fe2+concentration in the system with the addition of CA was maintained in the high range,making the FeⅡCA activation of（NH4）2S2O8to purify NO a continuous process.In the mechanistic study,the free radical inhibition experiments combined with the EPR assay further showed that hydroxyl radicals（·OH）play a major role in the purification of NO;the qualitative and quantitative analysis by ion chromatography and the determination of（NH4）2S2O8concentration to calculate the material balance of NO conversion and S2O82-conversion during the reaction showed that the main ionic products of the system for NO purification are NO3-and SO42-,and the actual values of the anionic product concentrations measured by quantitative analysis were consistent with the theoretical values obtained by calculation.The determination of the product salt by infrared spectroscopy showed that the salt component of the reaction product was mainly（NH4）2S2O8,with the incidental by-product of ferric ammonium citrate(C6H11Fe NO7),which can be used as an additive in fertilizers to meet the development of the green chemical industry.To improve the utilization of free radicals and to improve the purification effect of the system for NO.In this paper,a supergravity rotating packed bed was selected as the gas-liquid reaction device to enhance the gas-liquid mass transfer effect and improve the volumetric mass transfer coefficient to carry out experiments.The effects of gas flow rate,liquid-to-liquid ratio,supergravity factor and Fe IICA concentration on the NO purification rate and total volume mass transfer coefficient were investigated respectively,and the correlation equation between the total volume mass transfer coefficient and each influencing factor in the supergravity rotating packed bed was obtained from the experimental data.The experiments kept c（NO）around 550ppm,c（（NH4）2S2O8）around 0.2mol·L-1,and the initial p H of the absorption solution of 3.The following operating parameters were determined to be suitable:gas flow rate of 1m3·h-1,liquid to gas ratio of 0.1,high gravity factor of 76.80,and c（FeⅡCA）of 0.025mol·L-1;under these conditions,the system purified NO at a rate of 75.5%.The following correlation formula between the total volume mass transfer coefficient KGa and different influencing elements is established by regression analysis:KGa=0.37189G0.65139L0.41937β0.2820c B0.33076.This article confirms the feasibility of the FeⅡCA/（NH4）2S2O8system in wet denitrification under high-gravity conditions,which expands the application of persulfate advanced oxidation method in the field of wet denitrification and lays the foundation for the application of high-gravity rotating packed bed in persulfate advanced oxidation technology for wet denitrification. |
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