分子结构对天然有机质模型化合物在碳纳米管上吸附的影响

Effect of molecular structure on the adsorption of natural organic matter surrogates on carbon nanotubes

天然有机物(NOM)是一类广泛分布的具有不同分子量和结构的物质,能够分散和稳定碳纳米管(CNTs).然而,NOM结构对CNTs吸附机理的影响尚不清楚.了解碳纳米管(CNTs)对有机化合物吸附的机理,对于CNTs及其对其他污染物的环境行为和风险的预测和评估至关重要.本文研究了3种天然有机物(Natural organic matter,NOM)替代物没食子酸(Gallic Acid,GA)、丹宁酸(Tannic Acid,TA)和十二烷基苯磺酸钠(SDBS)在CNTs上的吸附性能.TA分子在CNTs上的摩尔质量浓度吸附较低,与它较大的三维立体分子结构形成的空间位阻有关.具有平面结构的GA和柔性脂肪链结构的SDBS分子容易与CNT结合,表现出在CNTs有更高的吸附.研究结果表明,模型化合物的分子结构对其在CNTs上的吸附有很大的影响.本研究通过研究分子结构对天然有机质模型化合物在碳纳米管上吸附的影响,指出NOM的分子结构是影响其环境吸附行为重要的因素.

Natural organic matters（ NOM） with diverse molecular weights and structures are ubiquitous in the environment. NOM-mediated dispersion and stabilization of carbon nanotubes（ CNTs） has been reported in previous studies. However,the effects of the NOM structures on the adsorption mechanism of CNTs are not clear. Understanding the sorption mechanisms of organic compounds on CNTs is a crucial process for assessing their environmental behavior and risks. In this study,gallic acid（ GA）,tannic acid（ TA） and sodium dodecyl benzene sulfonate（ SDBS） were chosen as the structural surrogates of NOM. Adsorption of TA on CNT was lower than the other two surrogates,prohably due to its structural rigidity. SDBS with a flexible long chain structure and GA with aplanar structure showed higher adsorption on CNTs surface due to alkane chain entanglement and subsequent surface alignment. The results showed that the molecular structure of the model compounds is dominant for their adsorption on CNTs. Therefore,molecular morphology of NOM must be considered regarding NOM mediated environmental behavior of CNTs.