Study On Preparation Of Biomass Activated Carbon For Adsorption Of Volatile Benzene Series

With the development of the chemical industry and economy,a large number of volatile organic compounds?VOCs?are released into the atmospheric environment.This is not only a serious threat to human health,but also leads to compound atmospheric pollution problems such as photochemical smog and urban haze.The treatment methods of organic waste gas mainly include recovery and elimination,among which carbon adsorption is one of the most widely used recovery technologies.This paper mainly studies the adsorption of industrial tar and VOCs by activated carbon.Typical volatile benzene compounds?toluene,phenol?are used as model compounds.The pore structure of biochar was regulated by chemical activation to increase the specific surface area of biochar.Thus enhancing the adsorption performance of biochar.At the same time,the mechanism and kinetic model of single and complex volatile benzenes adsorbed by biochar were investigated.In addition,saturated activated carbon adsorbents can be reused through thermal regeneration.The main conclusions are as follows:?1?This paper studied the preparation of rice husk based activated carbon by two-step method for adsorption of toluene,and investigated the physicochemical/structural characteristics and adsorption performance of activated carbon by different mass ratios of potassium hydroxide and biochar.Studies have shown that the alkali-carbon ratio has a great influence on the properties of activated carbon.When the mass ratio is 3:1,the activated carbon has a high specific surface area(S_BET:1818 m²/g)and is mainly dominated by a meso-micro multilevel pore structure.Thereby enhancing the toluene adsorption performance?penetration time:2784 min,adsorption capacity:1028.05 mg/g?.In addition,the adsorption of toluene by rice husk-based activated carbon conforms to a pseudo-secondary adsorption kinetic model.?2?In order to reduce the preparation steps of activated carbon and the dosage of activator,this paper studied the preparation of high-performance biomass?such as lignin,rice husk?activated carbon by one-step pyrolysis method for adsorption of toluene.Studies have shown that the original biochar has a low specific surface area.Mixed pyrolysis of biomass and potassium hydroxide?mass ratio 1:1?can significantly increase the specific surface area of biochar.In addition,adding polyvinyl chloride?PVC?can further increase the specific surface area of biochar.The specific surface area of lignin char is slightly higher than that of rice husk char.The maximum penetration time of lignin activated carbon?LPKC?for toluene adsorption was 2197.5 min and the saturated adsorption capacity was 1082.54 mg/g.?3?Sodium carbonate?K₂CO₃?and potassium oxalate?K₂C₂O₄?are less corrosive and can be used to replace potassium hydroxide?KOH?.In this paper,rice husk?RH?was mechanically mixed?mass ratio 1:1?with different potassium compounds?KOH,K₂CO₃ and K₂C₂O₄?,and high-quality bio-oil and activated carbon were prepared by one-step catalytic pyrolysis.Activated carbon is used for adsorption of volatile benzenes?toluene and phenol?.It was found that due to the excellent catalytic performance of potassium compounds,biomass decomposed in a low temperature range,and its catalytic activity order was KOH>K₂CO₃>K₂C₂O₄.Under high temperature pyrolysis conditions,K₂C₂O₄ is beneficial for the preparation of bio-oils with high levels of hydrocarbons.Due to the relatively mild activation process,RHC-K₂C₂O₄ has a maximum specific surface area of 1347 m²/g,a maximum toluene penetration adsorption time of 1230 minutes,and an adsorption capacity of 609.38 mg/g.In addition,activated carbon can effectively adsorb a toluene-phenol mixture.Among them,RHC-K₂C₂O₄ has the highest toluene adsorption capacity of 115.47 mg/g and phenol adsorption capacity of 531.95 mg/g.