Study On Structure-activity Relationship Of Activated Carbon Modification And Adsorption Of VOCs

The activated carbon adsorption method is usually used for the treatment of volatile organic compounds（VOCs）.It is shown that the structure of activated carbon has great influence on the risk of spontaneous combustion and the VOCs adsorption efficiency.In this paper,the quaternary ammonium based ionic liquids（ILs）and amino acid-based ILs were used to modify the physic-chemical structure of coconut-shell activated carbon,respectively.The structure-activity relationship between the activated carbon and adsorption efficiency before and after the modification were investigated.The thermal safety risks of VOCs adsorption by modified activated carbon were further explored.The quaternary ammonium salt based ILs and imidazole/proline i ILs were prepared to modified the activated carbon.It could optimize the structural properties of activated carbon.It also could improve the VOCs adsorption ability.The SEM,FT-IR,Boehm titration,BET and other methods were employed to characterize the microscopic and macroscopic properties of activated carbon,and the changes in physical and chemical properties of activated carbon before and after modification.The results of SEM showed that the modified activated carbon had more surface pores,increased pore size,and specific surface area.The results of FT-IR showed that there were new functional groups generated on the surface of activated carbon.The online adsorption device was used to study the adsorption performance of activated carbon before and after modification.The results showed that the toluene adsorption capacity of activated carbon modified with imidazole-proline and quaternary ammonium salt ILs were 78.00 mg·g^-1 and 113.12 mg·g^-1,respectively.They were 2.16 and 3.14 times of the toluene adsorption capacity of the original activated carbon(36.03 mg·g^-1).It demonstrated that the adsorption efficiency of activated carbon could be significantly improved by modification with ILs.The solid spontaneous ignition point tester was used to study the spontaneous combustion law of activated carbon before and after modification.The spontaneous ignition point temperature of activated carbon modified by imidazole/proline ILs was347.8oC,which was 19oC higher than that of original activated carbon.The time to reach the spontaneous ignition point was 10.85 h,which was 0.75 h longer than that of original activated carbon.The spontaneous combustion temperature of activated carbon was 355.1oC,which was 26.7oC higher than that of original activated carbon.The time to reach the spontaneous ignition point was 11.13 h,which was 1.03 h longer than that of original activated carbon.The thermodynamics of the toluene adsorption on activated carbon before and after the modification was studied by TG.The activation energy of activated carbon modified by imidazole-proline and quaternary ammonium salt ILs after adsorption were 57.11 k J·mol^-1,and 47.32 k J·mol^-1,respectively,which were 1.39 and 1.14 times of the original activated carbon(41.35 k J·mol^-1).The thermal safety risk of VOCs adsorption with activated carbon was significantly reduced.The results of the research provide theoretical support for the efficient and safe operation of VOCs adsorption by activated carbon.