【作者】 孙倩；

【导师】 盛连喜； 陈景文；

【作者基本信息】 东北师范大学 ， 环境科学， 2013， 博士

【摘要】 碳基纳米材料（CNMs）因有着比传统材料更加优异的性质，而被广泛应用于生产生活中。CNMs可以被释放到在环境中，在环境中迁移和转化，对环境和人类健康有潜在的风险。因此，研究CNMs的环境行为，进而评价CNMs的环境风险具有重要意义。已有研究表明，CNMs可以在水中稳定存在，特别是在天然水体中，CNMs可以通过吸附溶解性有机质（DOM）、有机污染物和生物大分子等而稳定悬浮。但DOM种类众多，环境行为复杂，影响CNMs吸附的因素多样，现有传统的实验和理论方法不仅无法直观地了解CNMs对DOM的吸附，而且难以揭示CNMs在水中吸附DOM的微观机理。抗生素作为一类新兴的有机污染物在水环境中也可以被CNMs吸附并存在与DOM同样的问题。本论文采用一种分子模拟方法——分子动力学（MD）方法，以C₆₀、单壁碳纳米管（SWNTs）、9种低分子量天然有机酸（LOAs）、单宁酸和磺胺甲恶唑为目标化合物，综合考虑了DOM和磺胺甲恶唑的种类、不同解离形态和浓度对CNMs吸附DOM和磺胺甲恶唑的影响，计算模拟了CNMs对DOM和磺胺甲恶唑的吸附作用，以此揭示CNMs与DOM和磺胺甲恶唑相互作用的微观机制，从而预测CNMs在水环境中对DOM和抗生素的吸附行为，为评价CNMs在水中的暴露行为提供理论依据。DOM是复杂的混合物，其中不仅有结构复杂的高分子量有机酸，也有结构相对简单的低分子量有机酸，而已有的研究缺乏低分子量有机酸对CNMs在水中稳定性影响的研究。本论文考察了真空和水中C₆₀与9种LOAs的相互作用，建立了C₆₀与LOAs相互作用能（Eint）的预测模型。MD模拟结果表明，真空和水中LOAs分子很好地吸附在C₆₀表面，芳香类LOAs与C₆₀的相互作用比脂肪类LOAs与C₆₀的强。LOAs分子量越大，C₆₀与LOAs的相互作用越强。水中不同解离形态的LOAs与C₆₀的相互作用不同，分子比离子的强。Eint模型有很好的拟合优度和稳健性，可用来预测LOAs与C₆₀的相互作用能。C₆₀和LOAs的主要相互作用是色散、诱导和疏水作用。为了考察MD模拟时真实水分子对C₆₀吸附LOAs的影响，本论文采用显性溶剂方法考察了水中柠檬酸和没食子酸在C₆₀上的吸附。结果表明，水中柠檬酸和没食子酸均能很好地被C₆₀吸附，柠檬酸和没食子酸与C₆₀的主要相互作用是范德华和疏水相互作用，没食子酸比柠檬酸更易吸附到C₆₀表面。吸附平衡后，柠檬酸和没食子酸可与水分子形成氢键，而氢键作用不是C₆₀吸附柠檬酸和没食子酸的主要作用。柠檬酸离子与C₆₀的作用比柠檬酸分子的弱。大分子的DOM与CNMs相互作用更强，它们是DOM影响CNMs在水中稳定性的关键成分。大分子DOM结构复杂，且其与CNMs的作用机制尚不清楚。本论文以单宁酸为DOM类似物，在充分考虑了单宁酸浓度和SWNTs直径对SWNTs吸附单宁酸影响的情况下，研究了SWNTs对单宁酸的吸附。结果发现，SWNTs可以很好地吸附水中的单宁酸，它们的主要相互作用是π-π和疏水相互作用，SWNTs还可以吸附多层单宁酸分子，它们的主要相互作用与SWNTs吸附单层单宁酸分子时相同。水分子可在同一个或多个单宁酸分子间起架桥作用。SWNTs与没食子酸的相互作用随SWNTs比表面积增大而增强，与SWNTs的直径无关。抗生素广泛存在于环境中，它们可能会与DOM一样，与环境中CNMs相互作用，影响彼此在环境中的行为。本论文选取一种抗生素——磺胺甲恶唑，分别研究了SWNTs和羧基修饰的SWNTs对磺胺甲恶唑的吸附，并在研究中考虑了不同解离形态磺胺甲恶唑、磺胺甲恶唑浓度和离子强度对SWNTs吸附磺胺甲恶唑的影响，羧基修饰SWNTs的氧质量百分比对羧基修饰的SWNTs吸附磺胺甲恶唑的影响。结果表明，不同解离形态磺胺甲恶唑与SWNTs的相互作用强弱为：阳离子>分子>阴离子。磺胺甲恶唑阴离子与SWNTs的主要相互作用为π-π和疏水相互作用。磺胺甲恶唑浓度和离子强度对SWNTs吸附磺胺甲恶唑阴离子的影响不大。羧基修饰的SWNTs与磺胺甲恶唑的相互作用比SWNTs与磺胺甲恶唑的弱，羧基修饰SWNTs的分子形态与磺胺甲恶唑分子的相互作用能和羧基修饰SWNTs的氧质量百分比成正相关关系，而羧基修饰SWNTs的离子形态与磺胺甲恶唑阴离子的相互作用能和羧基修饰SWNTs的氧质量百分没有此规律。羧基修饰SWNTs吸附磺胺甲恶唑时形成的氢键比SWNTs吸附磺胺甲恶唑时形成的多。SWNTs上的羧基只是减少了SWNTs的疏水表面，并没有减弱SWNTs与磺胺甲恶唑的相互作用。更多还原

【Abstract】 Carbon nanomaterials （CNMs） are widely used in our daily production and life due totheir desirable characters. When released to the environment, CNMs can pose detrimentaleffects to both the environment and human health. To evaluate the environmental risks ofCNMs, it is important to investigate their environmental behaviors. Previous studies show thatCNMs can suspend in water, especially in natural water. Moreover, it has been reported thattheir suspensions are even more stable when they adsorb dissolved organic matter （DOM）,organic contaminants or biomacromolecule in the water. However, due to the complexity ofthe DOM structure and component, with the existing experimental and theoretical methods,investigations on the morphology and mechanisms of the interactions between CNMs andDOM are rather difficult. In this study, a method for molecular modeling molecular dynamics（MD） was employed to simulate the adsorption of DOM on CNMs. Moreover, as an emergingorganic contaminant which can also be adsorbed by CNMs, the adsorption of antibiotics onCNMs was also demonstrated. C₆₀, single-walled carbon nanotubes （SWNTs）,9lowmolecular weight organic acids （LOAs）, tannic acid and sulfamethoxazole were chosen as thetarget compounds. The effects of species, different dissociative forms and the concentrationsof DOM and sulfamethoxazole to their adsorptions on CNMs were elucidated. Theseinvestigations were dedicated to reveal the mechanisms of the interactions between CNMsand DOM/sulfamethoxazole, and to provide primary data for the evaluation of the exposedbehavior of CNMs in water.DOM is a complex mixture, which includes high-molecular-weight organic acids andlow-molecular-weight organic acids. However, data on the effect of LOAs on the stability ofCNMs in water is rather limited. Hereby, the interactions of9LOAs with C₆₀in vacuum andwater were simulated. Predictive models on the interaction energy between LOAs and C₆₀were developed. MD simulations indicate that LOAs could be well adsorbed on C₆₀both invacuum and water conditions. Moreover, the aromatic LOAs have stronger interactions withC₆₀than the aliphatic LOAs, and the LOA molecules have stronger interactions with C₆₀thanthe corresponding LOA anions. The models of the interaction energy between LOAs and C₆₀show good goodness-of-fit and robustness. On the other hand, the dominating interactions ofLOAs with C₆₀are dispersion, induction and hydrophobic interactions.To evaluate the effect of real water molecules on the adsorptions of LOAs on C₆₀, theadsorptions of citric acid and gallic acid on C₆₀in water were also simulated with MD. Theseresults show that both acids were also firmly adsorbed on C₆₀, and the dominating interactionsare van der Waals and hydrophobic interactions. However, gallic acid has stronger interactions with C₆₀than citric acid. Furthermore, hydrogen bonds were formed when citric acid andgallic acid interacted with water. Nevertheless, hydrogen bonds are not the dominatinginteractions, besides citric anion has stronger interactions with C₆₀than citric molecule.The interactions of high-molecular-weight organic acids with CNM are stronger, whichlead to their significant higher stability on the CNMs in water. However, the mechanisms ofinteractions between DOM and CNMs are still unclear. Therefore, in this dissertation, theadsorptions of tannic acid at different concentrations on SWNTs were simulated, with thediameter of SWNTs as another influence factor. The results show that tannic acid could bewell adsorbed on SWNTs, and their dominating interactions are π-π and hydrophobicinteractions. Moreover, multilayer adsorption phenomena of several tannic acids on SWNTswere detected, and bridge effect was observed between the water molecule and the tannicacids. Furthermore, the sorption affinity of SWNTs for gallic acid was enhanced with anincreasing surface area of SWNTs, and shows no direct relation to the diameter of SWNTs.Antibiotics can be adsorbed by CNMs, hence, their environmental behavior should beevaluated together than individually. The adsorptions of sulfamethoxazole on SWNTs andcarboxylic SWNTs were simulated respectively, and the effects of different dissociative formsof sulfamethoxazole, concentration of sulfamethoxazole and ionic strength on the adsorptionswere considered. Moreover, the effect of oxygen mass percent of carboxylic SWNTs on theadsorptions was also investigated. The results show that the orders of interactions of differentdissociative forms of sulfamethoxazole with SWNTs were: cation> molecule> anion. Themain interactions of sulfamethoxazole with SWNTs are π-π and hydrophobic interactions.However, the effects of concentration of sulfamethoxazole and ionic strength on theadsorptions were no significant, while the interactions of sulfamethoxazole with SWNTs arestronger than with carboxylic SWNTs. Sorption affinity of the molecules of carboxylicSWNTs for sulfamethoxazol increases with an increasing oxygen mass percent of carboxylicSWNTs, and the sorption affinity of the dissociative form of carboxylic SWNTs is not relatedto the oxygen mass percent of carboxylic SWNTs. Hydrogen bonds betweensulfamethoxazole adsorbed by carboxylic SWNTs and water occurs more than those betweensulfamethoxazole adsorbed by SWNTs and water. Carboxyl group of SWNTs only reduce thesurface area of SWNTs, but it does not affect the adsorption affinity of SWNTs.更多还原