Study On The Preparation Of Activated Carbon And The Effect Of Its Physicochemical Properties On The Adsorption Of VOCs

In this paper,a series of nano activated carbon materials were prepared by one-step rapid pyrolysis activation method and one-step physical-chemical activation method.The relationship between the pore structure formation of activated carbon and the preparation process and activator used was studied,and the pore formation mechanism was elaborated in detail.Three typical VOCs,including ethyl acetate,toluene and p-xylene,were selected as the simulated pollution gases to carry out the single adsorption experiment in a constant temperature fixed bed.The adsorption performance of the prepared activated carbon was measured,and the relationship between the physical and chemical properties of the activated carbon and the adsorption performance was analyzed.The specific contents and conclusions include the following aspects:Activated carbon powder was prepared from coconut shell by one-step rapid pyrolysis activation method.Effects of temperature and the activation atmosphere（oxygen and steam content）on the pore structure of the ACPs was researched by the designed single variable experiment conditions,as the temperature ranged from 700℃to 1000℃,oxygen content ranged from 0 vo L.%to 8 vo L.%and steam content ranged from 0 vo L.%to 30 vo L.%.The pore structure and surface characteristics of ACPs were characterized by bet and SEM.Research shows that all three factors motivated the development of the overall porosity.The porosity presented a nearly linear augment from 700℃to 1000℃,but this augment tended to slow down when temperature higher than 900℃.As oxygen content varied from 0 vo L.%to 8 vo L.%,the porosity presented a nearly logarithmic growth,and the microporosity had got better development than the mesopores and macropores.Steam had increased both micropores and mesopores during content less than 20 vo L.%,while it changed to restrain the evolution of the porosity under content higher than 20 vo L.%.Under 1000℃-6%oxygen-20%steam condition,the prepared ACPs had the largest specific surface area and total pore volume of 415.85 m²/g and 0.175 cm³/g.Three kinds of activated coke powders（ACPs）were prepared from different coals by one-step rapid pyrolysis activation method.Detailed pore structure and surface characteristics of the ACPs were characterized by BET,SEM and FTIR.The adsorption properties of ACPs for ethyl acetate,benzene and p-xylene were analyzed.The results show that ACP samples have large specific surface area,pore volume and excellent pore structure.Volatile contents in the feed coal had promotion effect on the fast formation and development of the pore structure.SLC showed the largest specific surface area and pore volume,which reached 351.07 m²/g and 0.1698 m³/g,separately.The surface of ACPs is rich in-COOH,-COOR,-OH（or R-O-R’）and C=O functional groups.The types of these functional groups are relatively stable regardless of the change of raw coal.ACPs have good adsorption for VOCs.Among them,the adsorption capacity of ethyl acetate,benzene and p-xylene is the largest,which is SLC sample,which is 222.23mg/g,149.87 mg/g,217.63 mg/g,respectively.All the ACP samples presented preferential VOC adsorption order of ethyl acetate>p-xylene>benzene,which suggested that ACPs presented favorable adsorption ability to VOC species of polar and large molecules.Several kinds of activated carbon materials were prepared from Heishan coal by one-step chemical physical activation method.The effects of the weight ratio（Fe（NO₃）₃:coal）on the physicochemical properties of the activated carbon were systematically investigated,and the ACs samples were detected by N₂adsorption-desorption,SEM,XRD,Raman and FTIR.Furthermore,The adsorption properties of ethyl acetate were studied.The results indicated that as the ratio increasing from 1:8 to 1:2,the specific surface area,total pore volume and micropore volume first increase and then decrease,the specific surface area increased from 560.86m²/g to 685.90 m²/g and then decreased to 299.56m²/g.The total pore volume and micropore volume increased from 0.29cm³/g,0.17cm³/g to 0.30cm³/g,0.22cm³/g,and then decreased to 0.16cm³/g and 0.10cm³/g,respectively.In the activation process,The iron ions would be infiltrated into the activated carbon could significantly promote the development of pore structure,especially the pores with pore size between 2.5-3nm,which enhance the adsorption capacity of ethyl acetate.It is worth noting thatthe ACs had the largest specific surface area and total pore volume of 685.90 m²/g and 0.30cm³/g under the 900℃,20 vol.%CO₂,the ratio is 1:5),the maximum adsorption capacity of ethyl acetate was 962.62mg/g.Activated carbon powder was prepared by one-step chemical physical activation in an open vacuum tube furnace.A series of biomass activated carbons were prepared with poplar sawdust as raw material and Fe（NO₃）₃and CO₂as activators.The effects of different mass ratios of Fe（NO₃）₃and poplar sawdust on the pore structure of ACPs were studied.The adsorption capacity of ACP was determined by simulating VOCs with ethyl acetate.The results show that Fe-AC-0.3 has the largest pore volume and specific surface area of 0.26cm³/g and 455.36m²/g,respectively.When the mass ratio is 0 to 0.3,the porosity increases linearly,but when the mass ratio is higher than 0.3,the porosity decreases.ACPs presented good VOCs adsorption performance.With the most micropore structures,Fe-AC-0.3 sample presented the best adsorption capacity for ethyl acetate,which is 712.58 mg/g.