Study On The Mechanism Of Denitrification By Activated Carbon Activated By Chemical-physical Metho

Activated carbon has unique pore structure and surface properties,and the material is easy to obtain,easy to operate,large adsorption capacity,stable property,can effectively remove NO_x and other pollutants in the flue gas,there are important applications in the field of flue gas purification.The pore volume of ordinary activated carbon is small,the distribution of micropores is wide,and the specific surface area is small,resulting in its adsorption performance can not meet the deep purification requirements of flue gas.The activation of activated carbon can optimize the pore size,improve the porosity,improve the surface acidity,and improve the adsorption performance of activated carbon.In this paper,coconut shell activated carbon as raw material,using orthogonal design to formulate experimental conditions,respectively chemical activation,physical activation and chemical-physical activation.At the same time,SEM,BET and FTIR were used to characterize the surface physical and chemical properties of activated carbon before and after activation,and orthogonal test was used to analyze the interaction between the levels of various factors to study the influence of different activation conditions on the denitrification performance of activated carbon.The main research contents are as follows:ZnCl₂,H₃PO₄and KOH were used for for chemical activation,it was found that Zn Cl₂activation easily blocked the micropores of activated carbon and destroyed the original structure,resulting in the overall low denitrification rate of activated carbon after activation.After H₃PO₄activation,the denitrification rate of activated carbon decreased with the increase of H₃PO₄concentration.KOH activation introduced some oxygen-containing functional groups to improve its adsorption performance.The orthogonal experiment shows that the type of activator has the most obvious effect on the denitration rate,while the concentration of activator has little effect on the denitration rate.The optimum chemical activation condition was activated by 3mol/L KOH at 80℃for 3.5 h.N₂,CO₂and air were used for physical activation.It was found that after N₂activation,the pore wall of activated carbon was smooth,the average pore diameter was increased,and the introduction of nitrogen-containing functional groups was conducive to improving the denitrification rate of activated carbon.CO₂activation is easy to cause the loss of pore structure of activated carbon,surface pores are messy and clogged seriously,resulting in low denitrification rate.Some new pores were formed on the surface of activated carbon after air activation,and oxygen-containing functional groups were introduced,but the strong oxidation at high temperature would lead to the pore wall collapse of activated carbon.The orthogonal experiment showed that the type of activated gas had the most significant effect on the denitrification performance of activated carbon,and the activation temperature had the least effect on the denitrification rate of activated carbon.The optimal physical activation conditions were as follows: 60 min activation at 225℃ N₂ atmosphere.KOH was used as the first activation reagent,and N₂,CO₂ and air were used as the second activation gas for chemical and physical activation.It was found that the average pore size of activated carbon increased after KOH-N₂ activation and the introduction of nitrogen-containing functional groups effectively improved the denitrification rate,but high temperature would cause structure collapse.After KOH-CO₂ activation,the pore size distribution of activated carbon is dense,the specific surface area and the total pore volume are large,and the functional groups such as C=C are introduced into the surface,and the denitration rate is greatly improved.After the activation of Koh-air,the porous structure of activated carbon was effectively developed,but part of the pore diameter was blocked,the specific surface area was small,oxygen-containing functional groups were introduced into the surface,and the denitration rate increased significantly.The results of orthogonal test showed that the denitration performance of chemically and physically activated activated carbon was most significantly affected by the activation time and least affected by the activated gas type.The optimal chemical and physical activation conditions were as follows:activation with 3mol/L KOH for 60 min,and then activation under CO₂ atmosphere at150 ℃ for 60 min.