Purification of Multi-Walled Carbon Nanotubes
- 海洋环境－已发表论文 
用 90 0℃高温氢气处理以及 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多壁碳纳米管 (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.经过纯化的MWCNTs的吸水率远小于活性碳 ,比CarbopackB稍大 ,比表面积和CarbopackB相近 .苯、正己烷、乙醇、丙酮四种化合物在纯化的MWCNTs填充色谱柱上的脱附率和CarbopackB的相同 .经纯化的MWCNTs的Ni残留量为 3 0 μg/g ,Mg残留量低于检测限 (10 μg/g) .由于管腔的存在 ,纯化的MWCNTs对有机物的保留能力大于CarbopackB .它可以作为气相色谱固定相和吸附挥发性有机物的吸附剂Multi walled carbon nanotubes (MWCNTs), prepared by catalytic decomposition of methane, were purified sequentially with hydrogen gas at 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, acetone on columns packed with the MWCNTs in different purification steps were also investigated. The morphologies of the MWCNTs in different purification steps were studied with TEM. The results suggest 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. After the treatment of hydrogen, it was very easy to remove Ni residual in MWCNTs, which could not be removed by hydrochloric acid reflux only. The water adsorbing capacity of the purified MWCNTs was much lower than that of activated charcoal, slightly higher than that of Carbopack B. The surface area of the purified MWCNTs was similar to that of Carbopack B. The desorption ratios of benzene, n hexane, ethanol, acetone on column packed with the purified MWCNTs were the same as those of Carbopack B. The amounts of Ni and Mg remained on the purified MWCNTs were 30 μg/g and were not detected (<10 μg/g), respectively. Due to its hollow cavities inside, the purified MWCNTs have stronger retention ability than Carbopack B. The purified MWCNTs are found to be a suitable packing material for gas chromatography and a sorbent in trapping volatile organic compounds from air.