Chen Wei, Duan Lin, Zhu Dongqiang
Tianjin Key Laboratory of Environmental Remediation and Pollution Control/College of Environmental Science and Engineering, Nankai University, Tianjin 300071, China.
Environ Sci Technol. 2007 Dec 15;41(24):8295-300. doi: 10.1021/es071230h.
Understanding adsorptive interactions between organic contaminants and carbon nanotubes is critical to both the environmental application of carbon nanotubes as special adsorbents and the assessment of the potential impact of carbon nanotubes on the fate and transport of organic contaminants in the environment. The adsorption of organic compounds with varied physical-chemical properties (hydrophobicity, polarity, electron polarizability, and size) to one single-walled carbon nanotube (SWNT) and two multiwalled carbon nanotubes (MWNTs) was evaluated. For a given carbon nanotube, the adsorption affinity correlated poorly with hydrophobicity but increased in the order of nonpolar aliphatic < nonpolar aromatics < nitroaromatics, and within the group of nitroaromatics, the adsorption affinity increased with the number of nitrofunctional groups. We propose that the strong adsorptive interaction between carbon nanotubes and nitroaromatics was due to the pi-pi electron-donor-acceptor (EDA) interaction between nitroaromatic molecules (electron acceptors) and the highly polarizable graphene sheets (electron donors) of carbon nanotubes. Additionally, we attribute the stronger adsorption of nonpolar aromatics compared to that of nonpolar aliphatics to the pi-electron coupling between the flat surfaces of both aromatic molecules and carbon nanotubes. For tetrachlorobenzene, the bulkiest adsorbate, adsorption affinity (on a unit surface area basis) to the SWNT was much stronger than to the two MWNTs, indicating a probable molecular sieving effect.
了解有机污染物与碳纳米管之间的吸附相互作用，对于碳纳米管作为特殊吸附剂的环境应用以及评估碳纳米管对环境中有机污染物的归宿和迁移的潜在影响都至关重要。评估了具有不同物理化学性质（疏水性、极性、电子极化率和尺寸）的有机化合物对一种单壁碳纳米管（SWNT）和两种多壁碳纳米管（MWNT）的吸附情况。对于给定的碳纳米管，吸附亲和力与疏水性的相关性较差，但按非极性脂肪族＜非极性芳香族＜硝基芳香族的顺序增加，并且在硝基芳香族组内，吸附亲和力随硝基官能团数量的增加而增加。我们认为碳纳米管与硝基芳香族之间强烈的吸附相互作用是由于硝基芳香族分子（电子受体）与碳纳米管的高极化率石墨烯片（电子供体）之间的π-π电子供体-受体（EDA）相互作用。此外，我们将非极性芳香族比非极性脂肪族更强的吸附归因于芳香族分子和平坦的碳纳米管表面之间的π电子耦合。对于体积最大的吸附质四氯苯，其对SWNT的吸附亲和力（基于单位表面积）比对两种MWNT的要强得多，这表明可能存在分子筛分效应。
