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活性炭微孔结构对丁烷吸附的影响

14 2O12 were then dried for 12 h at 120℃tO remove water prior to characterizati0n. AC一3 and AC一6 are commercia1 wooden activated carbons,and AC-4 is commercial special carbon for gasoline adsorption,supplied by Sun- tar Active carbon (Jiangxi Province, China).AC一5,AC-7 and AC-8 are commerciaI shelI activated carbon. coaI granular activated carbon and bamboo charcoal,provided by Fengcheng Rongfeng Activated car- bon Co.,Ltd.,Xinhua Carbon industry Co.,Ltd.(Hebei Province,China)and Yuan-Ii Active Carbon Co.,Ltd.(Fujian Province,China),respectively.Most of the properties of activated carbons de- termined in this study were given In Table 1. Methods Characteristics of the materials The textural characteristics of the car- bon samples were obtained by physi- cal adsorption of N2 at-196 oC,which was carried out jn a volumetric system (ASAP 201 0),and the sample was de- gasified under vacuum(<1 04 atm)at 200 oC for 12 h.The specific surface area was calculated by BET method in the relative pressure range of 0-1,and the pore volume was estimated at the Iargest relative pressure.Micropore volume and pore size distribution were determined by Dubbin..Radushkev—— ich(DR1 equation and BJH adsorption branch[12】.and the density functional theory(DFT) Butane working capacity The BWC test was conducted using ASTM method D5228-92[ .The sample was packed in a constant volume bed as directed by the ASTM D2854-09 stan- dard procedure[15】.The bed was then held within a constant temperature bath at 25 oC with butane flowing at the rate of(250 ̄5)mI/min for 1 5 min.Sec・ ondly,the sample was weighed,and butane was adsorbed for additional 1 0 min,stopping at nearest 0.01 g gap between two adjacent weights.When a constant sample weight was reached, desorption was conducted by passing dry air through the sample bed at 300 ̄ 5 ml/min for 40 min.The mass difer- ence between the saturated and des- orbed adsorbent was the BWC in grams of butane per 1 00 mI carbon.A schematic representation of the ex- perimental apparatus was shown in Agricultural Science&Technology Fig.2. Iodine adsorption The iodine amo- unt was datermined according to GB 一 1 2496.8.1 9999 I1唰by using the sodium thiosulfate volumetric method.The ac- tivated carbon was ground and passed through 75 um-mesh screen,and stan- dard iodine solution was added over activated carbon(0.50 a).After shak— ing for 1 5 rain;the residuaI iodine concentration was determined by titra— tion using standard sodium thiosulfate with starch as an indicator.The iodine amount was defined as the quantity of iodine adsorbed(mg/g of carbon)at a residuaIiodine concentration. Methylene blue(MB)adsorption MB adsorption was directed bV GB,1_1- 2496.10—1999[悃.Carbon samples f0.1 g、were taken in 1 00 mI stoppered E卜 lenmeyer flasks and the substrate so— lutions of MB were added untiI the col一 0r Of MB turned to be vanished.Then. experiments were carried out in the shaker Iasting for 20 min.the residual concentration was analyzed by spec- trophotometer at 665 nm. Apparent density Apparent density Table 1 The specific parameters of carbon was determined on the basis of GB/1-- 1 2496.1—1 9999[1q.Using a granular sa・ mple,apparent density was date卜 mined by measuring the volume packed by a free fall into a 100 ml- graduated cylinder,determining the mass of the known volume. 

Results and Discussion Nitrogen adsorption/desorption is- otherms Due to the characteristic of the relatively small molecule diameter of nitrogen,nitrogen adsorption/desorp・ tion is considered as a standard proce- dure for characterizing porosity texture of carbonaceous adsorbents,frequently being used in probe porosity and sur- face area.The N2 adsorption/desorp- tion isotherms of 8 activated carbons were shown jn Fig.2.The jsotherms of AC一5.AC一6.AC一7 and AC一8 were very similar with the shape of curve. They were relatively flat and the hys- teresis loop was extremely narrow.Ac- cording to the IUPAC classification.It was typical type Iisotherm indicative of microporous materials.AC-1,AC.-2 

 ̄....t..o..r...b..a..th. 

Fig.1 Experimental design for butane working capacity test 

Vo1.13,No.1,2012 2012 15 and AC-4 showed type II isotherm characteristics,and AC一3 displayed typical type IV isotherm.In addition. AC一1一AC一5 revealed small hysteresis loop.which indicated that very part of mesopore was present and the capil・ lary condensation phenomenon taken place in mesopore.The loop of AC一3 was found to be Iarger.jndicating that the pore size distribution was wider. The micropore size distribution Fig.3 showed the micropore dis- tribution of activated carbons within two regions of 0-1.0 and 1.0-2.0 nm. separated by the boundary point 1.0 nm.Firstly.the pore in the range of 1.0-2.0 nm was analyzed.Eight sam- pies alI showed obvious peaks in the range of 1.16-1.40 nm.AC一5 and AC一7 were bimode1.with a reasonable ReIatire presstEe /P0】 Nitrogen adsOrp村0n—desOrptiOn isotherms of activated carbons Pore diameter II珊 Fig.3 Micropore size distributions of activated carbons 舅 呈 & 趸 嚣 量 Pore diameter//11111 Fig.4 The pore size between 0.5—1.0 nm distribution of activated carbons fraction of pore jn 1.16—1.6O nm.AI_ though AC一6 was bimodel,the pore was mainly Iocated in 0—1.0 nm.The rest activated carbon was multimodel, with most proportion of pores in the range of 1.2-1.6 nm.It could be seen that the pore with the size greater than 1.7 nm stilI had a c0nsiderabIe rate of growth in the pore volume.So.the pore distribution of activated carbons was mainly within 1.1 6—2.00 nm.Within the range,the cumulative pore volume percentages of total micropores were 77%,80%,81%,64%,60%,25%, 40%and 46%.respectively. Fiq.4 showed the pore size distri— bution within 0-1.0 nm.which mainly focused on a smalI range of 0.5-0.9 nm.Among them.AC一3 was unimoda1 with an obvious peak in about 0.7 nm. AC一1.AC一2,and AC-7 were biom— odel with most fraction at Q.65-0.8 nm. AC一4.AC一5。AC一6 and AC一8 showed multi—peak distribution in 0.4.0.6 and 0.8 nm.with a reasonable fraction of pore in 0.45-0.85 nm.The pore vol— ume of AC-6 in 0-1.0 nm was signifi- cantly greater than the other,and AC一 8 ranked the last.The order of the pore volume within 0-1.0 nm was shown as follows:AC-6>AC-5>AC-7>AC-1> AC-2>AC-4>AC一3>AC一8. The relationship between microp. ore structure and the butane ad— sorption performance N-butane adsorption on activated carbon is considered as a reversible physical process.The adsorption ca- pacity is affected by its physical struc- ture,such as pore volume,pore size and pore size distribution.Microporous structure of activated carbon had sig- nificant effect on the adsorption of bu- lane.and the results were shown in Table 2.It was clear that adsorption performance of activated carbon was mainly affected by specific surface 

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