Study On The Factors Affecting The Adsorption Of Toluene On Activated Carbon By Particle Size And Surface Modification

Volatile organic compounds(VOCs)in indoor air are extremely damaging to health.Therefore,how to remove these pollutants has become an important issue related to people's quality of life and health.At present,the use of activated carbon to adsorb these pollutants is a highly efficient,low-cost and extremely convenient method.Although predecessors have studied a lot about adsorption of VOCs,the reports on particle size and fine modification research can't fully meet the actual needs.As a typical volatile organic compound,human health is widely endangered by toluene.So,it can be used as a representative of VOCs processing.In this paper,the effect of particle size on the adsorption of toluene by activated carbon was studied,and the modification of activated carbon was carried out too.The particle size range of activated carbon with better adsorption capacity and the particle size range of activated carbon with better modification effect were found,and the adsorption reaction mechanism was explored.Finally,two desorption methods are used to regenerate activated carbon.There are certain economic reference value for activated carbon production and processing.The main contents are asfollows:The wood granular activated carbon which activated by ZnCl2 is classified into five sizes of 50 mesh or more,50-100 mesh,100-200 mesh,200-300 mesh,and 300 mesh or less using a standard sieve.The adsorption experiment was carried out by using the established activated carbon dynamic adsorption toluene device.As the particle size of activated carbon decreases,the amount of toluene adsorbed increases gradually.Through the BET total analysis of activated carbon,it was found that the specific surface area,as well as micropore surface area and volume of activated carbon increased with the decrease of particle size.It is in the best economic interest to process activated carbon to about 100 mesh.In this paper,the activated carbon was modified by NaOH solution,and the modification effect is better under the condition of NaOH solution concentration of 0.1 mol/L,solid-liquid ratio of 1:20 g/mL as well as soaking for 12 hours.By performing BET total analysis and surface chemical functional group determination on the modified activated carbon,the date demonstrates that the micropore surface area as well as volume and specific surface area of the modified activated carbon are reduced,and acidic sites on the surface are reduced.It is indicated that the specific surface area,micropore surface area as well as volume and acidic sites on the surface of activated carbon jointly affect the adsorption performance of toluene.The Langmuir and Freundlich adsorption isotherms are used to correlate the results,and the Bangham model is used to analyze the pore diffusion during the adsorption process.The reaction kinetics of adsorption of toluene on activated carbon is studied.The pseudo-first-order adsorption kinetics model and pseudo-secondary adsorption kinetics model are used respectively.The experimental results show that the adsorption of toluene on activated carbon conforms to the first type of isothermal adsorption curve,and the monolayer adsorption based on microporous adsorption.The adsorption process of toluene on activated carbon conforms to the Langmuir and Freundlich adsorption isotherms and meets the pseudo-first-order adsorption kinetics.The pore diffusion mechanism is also consistent with the Bangham model.At last,the activated carbon is regenerated by nitrogen purging and high-temperature thermal desorption.The result shows that the high-temperature thermal desorption method is more suitable for modified activated carbon,and the adsorption capacity is still 70.54%of the new activated carbon after 5 times of regeneration.