不同性质有机质悬浮的纳米碳管对有机污染物行为的影响

Nanotechnology has become one of the most promising new technologies in the 21st century. Engineered nanomaterials will inevitably be released into the environment during manufacturing, application or disposal, and may become a very important component of the environment. As an important member of engineered nanomaterials, carbon nanotubes (CNTs) are used in many areas with very increasing production due to their unique properties. Unfortunately, CNTs have been demonstrated to be toxic to various organisms. In addition, the strong interaction between CNTs and various pollutants significantly alters the mobility, bioavailability, and toxicity of both CNTs and pollutants. Therefore, the widespread of CNTs can lead to unforeseen health and environmental risks. The co-existence of CNTs and dissolved organic matter (DOM) could widely occur in the environment because of the ubiquity of DOM and the increasing application of CNTs. DOM has been reported to effectively suspend CNTs by "unzippering" or DOM coating mechanism. The mobility and transport of dispersed CNTs and CNT-adsorbed organic chemicals could subsequently be promoted in natural aqueous environments, potentially enhancing the spread of various organic chemicals and their environmental risk. Most of studies focused on the apparent total sorption of organic pollutants on CNTs. The coating of DOM on CNTs was emphasized as the major effect on organic pollutants sorption. However, the key information that is missing is the sorption of organic pollutants on the suspended CNTs. Our primary study showed that although the mass of suspended CNTs was very low, their contributions to organic chemicals sorption were significant. Additionally, sorption characteristics of the suspended CNTs may be different depending on the properties of DOM such as polarity, composition and structure. But no study directly reported the sorption characteristics of the suspended CNTs as affected by DOM with different properties and their potential importance to the behavior and risk of organic contaminants and CNTs themselves. Therefore, in this study, the dissolved humic acids will be used as model DOM to investigate the effects of pH, ionic strength, DOM polarity, composition and structure on dispersing mechanism of CNTs and sorption of organic pollutants on suspended CNTs. The sorption of organic pollutants on suspended and aggregated CNTs will be compared to determine the contribution of suspended CNTs to overall sorption of organic pollutants. The different sorption characteristics of suspended CNTs as affected by different dispersing mechanisms may control the contribution of suspended CNTs to sorption of organic pollutants. This work will establish a fundamental and useful database for environmental risk assessment of organic pollutants - suspended CNTs system and provide new insight for application of CNTs as a potential adsorbent in environment protection.

环境地球化学过程中形成的溶解有机质（DOM）在性质上存在很大的差异。根据不同性质，DOM可能通过胶束包裹或"拉拉链"的方式使纳米碳管（CNTs）悬浮。以往研究主要关注有机污染物在CNTs上的表观吸附过程，对不同分散机制下悬浮的CNTs与污染物的相互作用关注不够。初步研究表明，尽管悬浮的CNTs所占比例很低，但其对吸附的贡献非常显著，因此，理解CNTs悬浮方式对污染物行为的影响可能才是控制CNTs行为和风险的关键环节。本申请拟以溶解胡敏酸为代表性DOM，系统考察pH、离子强度、DOM极性、结构等对DOM分散CNTs机制的影响，进而评价不同机制下悬浮CNTs的吸附特征。重点比较悬浮的CNTs与聚合的CNTs对污染物吸附性能的差别，定量不同机制悬浮的CNTs在表观吸附中的贡献，为有机污染物-CNTs体系的环境风险评价建立数据储备，并为CNTs作为高性能吸附剂在环境学中的应用提供理论基础。

环境地球化学过程中形成的天然有机质（DHA）在性质上存在很大的差异，包括极性、化学结构、分子量等。不同性质的DHA在纳米碳管（CNTs）上的吸附机理及其悬浮CNTs的能力差异很大，不能通过传统的胶束包裹或“拉拉链”机理笼统的解释，需要对悬浮机理进行更加系统的研究。理解CNTs悬浮方式及机理对污染物行为的影响是控制CNTs及其吸附的污染物的行为和风险的关键环节。.经过三年的持续研究，基本上实现了预期的科研目标，并在此基础上，针对发现的新问题，将研究内容进行了有效的扩展。本项目主要研究内容包括：不同性质、结构的DHA在CNTs上的吸附及其对CNTs的悬浮；悬浮CNTs对有机污染物的吸附；悬浮CNTs在液相中比表面积的测定；模型化合物在CNTs上的吸附及其对CNTs的悬浮。基于以上研究内容，取得的主要研究结果包括：.1、探明了DHA的结构特征是控制其自身吸附及悬浮CNTs的关键因素，空间位阻作用是主导的悬浮机制；.2、发现悬浮后的CNTs表现出对有机污染物极高的吸附性能，同时定量了不同机制悬浮的CNTs在表观吸附中的贡献；.3、通过核磁共振技术证实悬浮CNTs在液相中的比表面积远远高于未悬浮CNTs的比表面积；.4、与柔性模型分子相比，刚性模型分子具有较大的空间位阻，在CNTs上的吸附低，但具有较高的悬浮CNTs的能力。.在本项目的支持下，研究团队发表SCI期刊论文5篇，中文核心期刊论文7篇。以上研究结果为CNTs体系的环境风险评价建立了数据储备，并为CNTs作为高性能吸附剂在环境学中的应用提供了理论基础。