【作者】 李权龙；

【导师】 袁东星；

【作者基本信息】 厦门大学 ， 环境科学， 2003， 博士

【摘要】 自从性质独特的碳纳米管(CNTs)1991年被发现以来，许多科学家为之做了大量的研究工作。如今，CNTs的宏量合成已经实现，其应用研究显得越来越迫切。CNTs具有多孔的石墨结构，是一种潜在的高性能吸附剂。目前普遍使用的CNTs纯化方法是氧化法，由此法纯化的CNTs表面存有极性基团。当CNTs作为吸附剂使用时，这些基团会引起不可逆吸附。如果用还原法如氢气还原纯化CNTs，则可避免极性基团的生成。吸附剂在气相色谱分离和环境样品痕量有机物的富集等方面得到广泛的应用，发展新型的吸附剂是众多科学家努力的方向。因此，研究CNTs在气相色谱分离和环境样品痕量有机物的富集方面的应用有着重要的现实意义。本论文围绕CNTs的应用基础研究展开，所研究的内容和结果包括以下几个方面： 1．多壁碳纳米管(MWCNTs)的纯化 用900℃高温氢气处理和5mol／L盐酸回流的方法，纯化了一种由甲烷在Ni-Mg-O催化剂上裂解生长的MWCNTs，考察了不同纯化阶段MWCNTs的吸水率、比表面积、Ni和Mg残留量以及在不同温度下苯、正己烷、乙醇、丙酮四种化合物在MWCNTs填充色谱柱上的脱附率的变化，并用透射电镜观察了MWCNTs的形态。结果表明，高温氢气处理可去除MWCNTs的无定形碳和表面极性基团，使其比表面积和吸水率减小，同时可打开MWCNTs端口。高温氢气处理后，再用盐酸回流即容易去除MWCNTs中单用盐酸回流方法无法去除的Ni。PMWCNTs的Ni残留量为30μg／g，Mg残留量低于检测限(10μg／g)。经过纯化的MWCNTs(PMWCNTs)的吸水率远小于活性炭，比Carbopack B稍大，比表面积和Carbopack B相近。苯、正己烷、乙醇、丙酮四种化合物在PMWCNTs填充色谱柱上的脱附率和Carbopack B的相同。 2．PMWCNTs作为气相色谱固定相的性能研究 PMWCNTs、石墨化碳黑(Carbopack B)、涂渍5％(w／w)Carbowax 20M的PMWCNTs和Carbopack B、活性炭分别填装成气相色谱填充柱，比较它们分离多类有机化合物的性能。结果表明，PMWCNTs是一种性能优异的气相色谱固定相。与相同比表面积的Carbopack B石墨化碳黑相比较，它有更强的保留能力，适合于分析沸点相对较低的化合物;有更均匀的表面，表现为极性化合物亦可得到对称的峰形;理论塔板数较小。此外，和CarbopackB一样，PMwCNTs涂渍5%(w/w)的Carbowax 20M后可用来分离极性化合物，甚至是强极性的小分子有机酸。3.PMWCNTs作为环境样品中挥发性有机化合物(VOCs)吸附剂的性能研究 用泄漏体积(breakthrough volume，BTV)和回收率评价pMWCN孔对各类典型voCs的吸附性能。结果表明，和具有相同比表面积的石墨化碳黑carb叩ackB相比，由于管腔的存在，各化合物在PMWCNTs上有大得多的BTVs，可吸附挥发性强的化合物。各化合物在PMwCNTs上的回收率在80%一1 10%之间，且不受水分的影响。可见PMWCNTs是一种性能优异的吸附剂，可用来富集空气中的VOCs，也可以代替商品化的VOCARB 3000，用于吹扫一捕集系统，富集水样中的VOCsO4.PMWCNTs用于富集水样中有机磷农药残留的研究 采用离线固相萃取一Gc一PFPD检测方法，研究了由50mg的PMwCNTs装填而成的SPE柱对水中8种有机磷农药的富集性能，并将之与商品化的Oasis HLB柱(Ic。)、本实验室自行装填的石墨化碳黑sPE柱(50mg carbopackB)的性能相比较。结果表明，水溶性强的甲胺磷在本研究所用的3种SPE柱上的BTvs均小于IOmL(目标物浓度20林留L);敌敌畏、二嗦农、甲基对硫磷、毒死蜂、对硫磷在3种sPE柱上的BTvS均大于200mL(各目标物浓度1林g/L):碳纳米管柱对极性有机磷农药如敌百虫和乐果的保留能力高于石墨化碳黑柱而低于oasis HLB柱。用碳纳米管柱萃取1 00mL浓度为2协岁L的基底加标水样时，除了甲胺磷和敌敌畏外，6种有机磷农药的加标回收率均高于70%。分析实际水样时，碳纳米管柱萃取和三氯甲烷液一液萃取所得的结果一致。更多还原

【Abstract】 Since their discovery in 1991, carbon nanotubes (CNTs) have attracted great attention because of their unique properties. Nowadays, large-scale preparation of CNTs has been realized, the application of CNTs is getting more and more urgent. CNTs could be an excellent adsorbent due to their porous and graphitic structure. However, polar groups on the surface of CNTs, formed during the purification with oxidant, will result in irreversible adsorption of various compounds while CNTs are used as sorbent. Purification with reducing reagent may avoid the forming of polar groups on the surface of CNTs. It is well known that many sorbents have been widely applied in chromatographic separation and in the preconcentration of trace organic analytes in environmental samples. Tremendous effort has been made in recent years for seeking new sorbents. Therefore, the study of CNTs as a sorbent in the use of environmental analysis may bring a way out. The thesis focuses on the studies of properties and applications of CNTs. The work is summarized as follows:1. Purification of multi-walled carbon nanotubes (MWCNTs)MWCNTs, prepared by decomposition of methane with Ni-Mg-0 as the catalyst, were purified sequentially with hydrogen gas under high temperature (900 ℃) and hydrochloric acid (5 mol/L) reflux. The variations of surface area, water-absorbing capacity, amount of Ni and Mg residuals of the MWCNTs in different purification steps were investigated. The desorbing ratios of benzene, n-hexane, ethanol and acetone on the columns packed with MWCNTs in different purification steps were also investigated. The morphologies of MWCNTs in different purification steps were studied with TEM. The results suggested that the treatment of hydrogen could remove the amorphous carbon and the polar groups on MWCNTs, resulting in the decrease of surface area and water absorbing capacity and having the ends of MWCNTs cut. The water-adsorbing capacity of the purified MWCNTs (PMWCNTs) was much lower than that of activated carbon, and slightly higher than that of Carbopack B. The desorption ratios of benzene, n-hexane, ethanol, acetone on the column packed with PMWCNTs were the same as those of Carbopack B. The amounts of Ni and Mg remained on the PMWCNTs were 30 ug/g and not detected (<10 ug/g), respectively.2. Evaluation of PMWCNTs as the gas chromatographic packing materialThe PMWCNTs, graphitized carbon black (Carbopack B), activated carbon, PMWCNTs and Carbopack B modified with 5% (w/w) Carbowax 20M were used as gas chromatographic packing materials. Their characteristics for separation of some organic compounds were compared. The results showed that PMWCNTs is anexcellent packing material. Comparing to Carbopack B with the same surface area, PMWCNTs have the following characteristics: having stronger retention ability, suitable for the separation of compounds with relatively low boiling points, showing symmetric peaks for polar compounds due to its more homogeneous surface, having lower theoretical plate number. Like Carbopack B, PMWCNTs modified with 5%(w/w) Carbowax 20M can be used to separate polar compounds.3. Evaluation of PMWCNTs as a sorbent in trapping volatile organic compounds (VOCs) from environmental samplesThe evaluation was performed in terms of breakthrough volume (BTV) and recoveries of representative VOCs. Due to their hollow cavities inside, PMWCNTs were found to have much higher BTV than Carbopack B, and trap more volatile compounds. The recoveries of the tested compounds trapped with PMWCNTs were between 80%~110%, and not affected by humidity. PMWCNTs can be used as a sorbent not only in trapping VOCs from air but also in a purge-and-trap system to preconcentrate VOCs from water samples.4. Evaluation of PMWCNTs as a sorbent in solid phase extraction (SPE) to preconcentrate organophosphorous pesticides (OPPs) from water samplesOff-line SPE coupled with GC-PFPD was applied in this study. 50mg PMWCNTs were packed in an SPE cartridge for the extraction of 8 OPPs in water samples. BTVs an更多还原