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活性炭吸附VOCs与其孔结构构效关系研究.pdf

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分类号Q鱼垒2兰U D C密级一编号.十I初大·警CENTR AI, SOUTH UNIVERSITY硕士学位论文论文题目..噩性炭爨胜.姒埏曼一复熹孔煞煎.构.效关.系.蕊亵。学科,专业供热堡燃.氧二通风臻童调王程。研究生姓名趔焦导师姓名及专业技术职务垒熹溘熬一撬\Master。issertati。I III.I/I/I//.I///刁I/I/I/I/-//11J1////19/I////1711//18//111/Relationship Between VOCs Adsorption and Activated CarbonPore StructureApplicantLin一№LSupervisor.取Q瞳§曼鳕量I-勘垃mg.Major №确g№越№i豫触d.An一C她出№咖g里蜮n熙啦gted toThe Faculty of Central South Universityin Partial fulfillment the requirement for the Degree of MasterMay,201 1School of Energy Science and EngineeringCentral South UniversityChangsha,Hunan,P R.China原创性声明本人声明,所呈交的学位论文是本人在导师指导下进行的研究工作及取得的研究成果。尽我所知,除了论文中特别加以标注和致谢的地方外,论文中不包含其他人已经发表或撰写过的研究成果,也不包含为获得中南大学或其他单位的学位或证书而使用过的材料。与我共同工作的同志对本研究所作的贡献均已在论文中作了明确的说明。作者签名惟 日期赳年厶月』二_日学位论文版权使用授权书本人了解中南大学有关保留、使用学位论文的规定,即学校有权保留学位论文并根据国家或湖南省有关部门规定送交学位论文,允许学位论文被查阅和借阅;学校可以公布学位论文的全部或部分内容,可以采用复印、缩印或其它手段保存学位论文。同时授权中国科学技术信息研究所将本学位论文收录到中国学位论文全文数据库,并通过网络向社会公众提供信息服务。作者签名埠导师签 日期纽翠年_L.,E13-E摘要活性炭孔结构是影响其吸附性能的主要因素之一。本文首先选用四种商业活性炭,利用氮气等温吸附、扫描电子显微镜SEM和傅立叶变换红外光谱FTIR澳O试了活性炭的物化性质。以甲苯、丙酮为吸附质,在温度为298.15 K下进行了静态和动态吸附实验,研究了活性炭孔结构对其吸附性能、吸附动力学、表面覆盖率和吸附能的影响。结果表明活性炭的比表面积和孔容是其吸附性能主要影响因素,孔径在0.8nm--2.4 nin和1.67nnl~2.22 nnl之间的孔容分别与甲苯和丙酮吸附量之间存在较好的线性关系。在快速吸附阶段,活性炭微孔或微孔、中孔为吸附速率主要制约因素;在颗粒内扩散阶段,微fErn表面孔或微孔为吸附速率的主要制约因素;在多层吸附阶段,中孔和大孔为吸附速率的主要制约因素。活性炭孔结构对其吸附特定物质的吸附能产生影响,甲苯、丙酮表面覆盖率小的活性炭吸附能大。其次,选用三种活性炭作为吸附剂,1,2.二氯乙烷作为吸附质,研究了吸附质在活性炭孔中的扩散机理。结果表明活性炭在吸附1,2.二氯乙烷时优先利用微孔,并且在微孔容积无法满足吸附速率时开始利用中孔。微孔吸附贯穿吸附过程的外扩散阶段到颗粒内扩散阶段,而中孔利用据活性炭与吸附质结合作用的强弱分别贯穿吸附过程的多层吸附阶段和颗粒内扩散阶段、多层吸附阶段。活性炭中微孔、中孔和大孔的利用率与其极性呈负相关关系,而与其浓度呈正相关关系。最后,研究了活性炭孔结构对丙酮扩散系数的影响。结果表明活性炭穿透时间与其比表面积和总孔容积呈正相关关系。活性炭吸附丙酮时,其扩散速度的主要制约因素为knudsen扩散。四种活性炭的综合扩散系数在0.808·10。9 m2/s.0.905·10。9 m2/s之间,等效扩散孔径在0.82 nln.1.26 nln之间。丙酮在被活性炭吸附过程中,其扩散系数呈现先迅速增大而后逐渐减小的趋势。吸附质分子的有效扩散系数在数值上相当于其时均扩散系数。关键词活性炭,孔结构,吸附,动力学,线性相关度,扩散系数AB STRACTActivated carbon pore structure iS the main effects on its adsorptionproperties.Firstly,four kinds of commercial activated carbonACwereselected as samples,physical and chemical properties of the samples werecharacterized by Nitrogen Adsorption Isotherms; Scanning ElectronMicroscopySEMand Fourier Trans Infrared SpectroscopyFTIR.Toexplore effects of activated carbon pore structure on its adsorption properties,adsorption kinetics,surface coverage and adsorption energy,adsorption oftoluene,acetone on the selected samples were investigated with thermodynamicand kinetic s at 298.1 5 K.The results showed that activated carbonsurface area and pore volume were the main factors affecting its adsorptionproperties;there was a good linear relationship between adsorptive capacity andactivated carbon pore volume when aperture was 0.8 nnl一2.4 nnl and 1.67nm-一2.22 nnl during adsorption for toluene and acetone,respectively.Duringfast adsorption stage,adsorption rate was mainly restricted by activated carbonmicropores or micropores,mesopores;at intra-particles diffusion stage andmultilayer adsorption stage;micropores,surface pore or micropores andmesopores,macropores were the main constraints on adsorption rate,respectively.Activated carbon pore structure Can influence adsorption energythe smaller the toluene or acetone surface coverage,the higher the adsorptionene理;y was.Secondly,three kinds of commercial activated carbon were selected as thesamples,1,2-dichloroethane acted as adsorbent to study the diffusionmechanism of adsorbate onto activated carbon.The results showed thatmicropores were firstly used during activated carbon adsorbent 1,2-dichloroethane,micropores adsorbent occurred during the external diffusionstage to fast adsorption stage of adsorption.According to adsorption strength,mesopores adsorbent occurred dudng the multilayer adsorption stage andintra-particles diffusion stage,the multilayer adsorption stage.The utilization ofmicropores,mesopores,macropores were negatively correlated with adsorbatepolarity,which was positively correlated with adsorbate concentration.Finally,the effect of activated carbon pore structure on acetone diffusioncoefficient Was discussed.The results showed that the activated carbonpenetration time is positively correlated with its surface area and total pore¨volume.Diffusion rate is mainly restricted by Knudsen Diffusion whenadsorption of acetone onto activated carbon.The synthetically diffusioncoefjficient of tllese four activated carbons ranges from 0.808·l 0叫m7s to0.905·10一m2/s.and the equivalent diffusion pore size is 0.82 n/n一1.26 nnl.During the adsorption of acetone onto activated carbon,the diffusioncoefficient showed an upward trend,and then decreased;therefore,the effectivediffusion coefficient of acetone iS equivalent to timeaverage diffusioncoefficient.KEY WORDSActivated carbon,pore structure,adsorption,dynamics,linearcorrelation,diffusion coefficientm
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