纳米纤维素基气凝胶的结构调控及其对芳香族化合物的高效吸附行为

Preparation of green and highly efficient adsorbent with biodegradable and renewable naturally occurred resources is constantly an attractive research topic. This project describes an new cellulose-based porous aerogel that expressing highly efficiency on the adsorption of aromatic organic compounds. The suspension of cellulose nanofibrils (CNF) with high aspect ratio will be manufactured by a combination of high-pressure homogenizer and NaOH/urea/polyethyleneglycol pretreatments. Subsequently, CNF surface will be branched with β-cyclodextrin by using polyethyleneimine (PEI) as the bridging “space arm”. Finally, the vacuum freeze-drying method will be carried out to obtain the polyporous CNF-PEI-CD which will form well-defined host–guest complexes with pollutants. The effect on the morphology, lenth, aspect ratio of CNF will be discussed during the pretreatment process and the mechanism of the morphology and structure of the adsorbed material will be clarified. The spectrophotometer will be applied to quantitatively measure the content of aromatic organic compounds (e.g. phenol, benzene, bisphenol A) during adsorption process. Efficiency and model of adsorption will be calculated and constructed, respectively, toward the understanding of structure-property relationship of cellulose-based aerogel and the physical law and mechanism of adsorption behind. This study will provide insights for the preparation and analysis of new functional aerogels. Therefore, this project is valuable in fundamental researches and applications.

利用生物质资源制备“绿色”高效的环境友好型吸附剂一直是研究者关注的热点。在本项目中，申请者拟通过NaOH/尿素/聚乙二醇预处理与高压均质联用制备高长径比的纳米纤维素纤丝（CNF），以聚乙烯亚胺分子（PEI）作为连接臂，将醛基化的β-环糊精（β-CD）连接到CNF上，经过冷冻干燥制备多孔的纳米纤维素基气凝胶（CNF-PEI-CD）。利用β-CD的疏水空腔对芳香族有机物的识别与选择性，获得一种高效吸附材料。考察预处理对CNF的分散性、尺寸、长径比的影响，阐明纤维素基气凝胶的形貌与结构调控机制，利用分光光度计检测CNF-PEI-CD吸附剂对废水中有机污染物（如苯酚、氯苯、双酚A）的吸附情况。分析吸附机理，构建吸附模型，建立纳米纤维素改性气凝胶在吸附过程中的构-效关系，进而确定吸附规律与影响，为制备可重复使用的生物质基吸附剂提供重要数据。本项目不仅具有科学和技术价值，而且有应用前景。

水污染是人类面临的主要环境污染问题之一。开展和研究水环境中污染物去除的方法和技术，探索污染物治理的理论基础和实践应用具有重要意义，以纤维素为原料开发环境友好型吸附剂是可持续发展和实现农林生物质高值化利用的重要内容。本项目的主要研究内容包括：1、以化学预处理和机械处理相结合的方式制备高长径比的纳米纤维素。通过对纤维素氢键的破坏和机械的研磨，纳米纤维素的分散相对有序，结构整齐，形态较为均一，直径约为5-20nm。2、以聚乙烯亚胺PEI 分子作为连接臂，将改性的纳米纤维素与醛基化的环糊精β-CD反应，冷冻干燥后制备CNF-PEI-CD气凝胶吸附剂，结果表明，PEI和环糊精做为官能团，已经成功接枝到纤维素的分子链上。改性的纳米纤维素气凝胶具有良好的三维孔洞结构，热稳定性良好。3、改性气凝胶对污染物的吸附行为研究。结果表明，改性后的气凝胶对污水中有机物和重金属离子均具有良好的吸附行为，通过Langmuir 吸附方程和Freundlich 吸附方程进行拟合，采用准一级和准二级动力学方程来分析污染物浓度随时间的变化关系。结果表明，吸附过程遵循准二阶动力学方程和Langmuir模型，该气凝胶吸附是化学吸附过程。该研究为气凝胶的结构调控和吸附行为提供有价值的理论和实验依据，为生物质基吸附剂在污水治理方面应用提供有益探索。