The Effect Of Pore Structure Of Activated Carbon On N-butane Adsorption Performance And Adsorption Kinetics

With the rapid development of national economy and increasing human requirements ofenvironmental protection, in recent years, activated carbon has played more and more role inthe treatment of industrial waste,especially in the waste gas.Activated carbon for gas adsorpti-on has been widely used for solvent recovery, organic waste gas treatment, gas separation,gaspurification, energy storage field et al. Butane working capacity （BWC） has been generally ac-cepted to characterize the activated carbon gas adsorption performance, especially in evaluati-on of the adsorption capacity of volatile organic gases.However, research on the relationship ofactivated carbon and butane adsorption performance is so few.Therefore,the study exhibits asignificant meaning for development of activated carbon research and application.Main resear-ch contents and results are summarized as follows:（1） Firstly,the relationship of activated carbon pore structure and butane adsorption perfor-mance was studied.It was found that activated carbon pore structure significantly effected buta-ne adsorption performance and there was a certain positive correlation between them.The bigg-er the surface area and pore volume were, the greater the butane activity of activated carbonwas and the greater butane working capacity was. Butane adsorption properties of activatedcarbon was also affected by the pore size distribution. The pore in1.2～2nm of micropore and2～4nm of mesopore played a major role in butane adsorption. The greater the pore volume inthe range was,the higher butane working capacity was.In addition,the pore of0.5～1.0nm hadinfluence on butane retentivity. When butane activity was fixed,the pore volume of this rangeshould be decreased as much as possible to improve the butane working capacity.（2）The paper then focused on modification of activated carbon. KOH,NaHCO3and HNO₃solutions were chosen to be used as modifier.The effect of modification conditions on butaneadsorption of modified activated carbon was studied,including impregnation concentration,impregnation ratio, impregnation time, impregnation temperature.And orthogonal experiments were designed to get the best impregnated process,meanwhile the mechanism of impregnationmodification were researched by some analysis methods.Results showed that when theimpregnation agent was KOH solution,the order of factors was the mass concentration>impregnation ratio> impregnation temperature> impregnation time and that the best processwas mass concentration of2%, impregnation ratio of1/1,temperature of60℃and time of6h,which made butane working capacity have a increase of10.7g/L.When the agent wasNaHCO₃,the order is mass concentration>impregnation temperature>ratio> time and theoptimal process was the mass concentration of3%, dipping ratio of1/1.5,time of4h,temperature of80℃, as a result of improvement12.9g/L in butane working capacity.WhenHNO₃was used as another agent,the order was mass concentration> ratio>temperature>time,but adsorption performance of impregnated carbon was worse than mention abovemethod.Impregnated activated carbon was characterized by nitrogen adsorption, SEM, FT-IR,Boehm titration, pore size distribution.Nitrogen adsorption showed that activated carbonsurface area and pore volume had a certain change.SEM images showed impregnation madethe surface of activated carbon become uneven and have cracks, agglomeration.FT-IR andBoehm titration results displayed that the kind of surface functional group of activated carbondid not change,but the change of concentration of groups made adsorption properties have acertain increase and decrease.Pore size distribution analysis showed pores of impregnatedactivated carbon was expanded,collapsed and blocked,making the pore volume change,whichaffected the adsorption properties of activated carbon.（3）Last, butane adsorption kinetics of activated carbon was researched in detail.Resultsshowed that adsorption for butane is a rapid physical adsorption process which was coexistenceof adsorption and desorption.Experiment results showed that butane flow significantly affectedthe adsorption rate and adsorption time, but did not affect the saturated adsorption capacity ofactivated carbon.And the saturated butane adsorption capacity decreased with the increasingtemperature,which indicated that butane adsorption on activated carbon was an exothermicreaction. Moreover, it was also found that the sorption kinetics were satisfied with Banghamequation with R²>0.99of AC-1and AC-2. The value of q_e obtained through Bangham equation was very close to the value of experimental data.Therefore the ideal adsorption rate equationcould be obtained by data fitting.