基于外来入侵植物功能化改性的磁性生物质吸附剂的制备及其对水中重金属吸附机理研究

Spartina alterniflora and Solidago canadensis are harmful invasive plants in Eastern China, and their stalks are rich in cellulose, hemicelluloses and lignin. In addition, the hydrophilic groups of the cellulose surface are partly taken place by hydrophobic epoxy, which can strengthen fiber self-bonding. A large number of functional groups could be introduced into reactive hydroxyl groups by chemical modification, and then could be used as a water treatment adsorbent for heavy metal pollution. The modified biologic materials can effectively remove heavy metal ions from wastewater, but in addition to the difficult recovery, and consequently resulting to the decrease of adsorption performance. Spartina alterniflora and Solidago Canadensis are modified into biobased adsorbent by alkalization, etherification and graft copolymerization, and then chemical deposition method is applied to prepare magnetic biobased adsorbent by using biobased adsorbent as a precursor. The conditions of the preparation process are studied systematically, and the modification mechanism is investigated. Adsorption and desorption characteristics of typical heavy metals from aqueous solution using magnetic biobased adsorbent are evaluated in batch experiments, and heavy metals purification mechanism is analyzed. A series of research steps are gradually carried out on the accumulation mechanism of saturation magnetism and functional group, structure-activity relationship of functional group and heavy metals, and practical application of magnetic biobased adsorbent. These results will provide the theory and scientific basis for practical application of magnetic biobased adsorbent.

互花米草和加拿大一枝黄花是我国华东地区危害较为严重的外来入侵植物，其秸秆富含纤维素、半纤维素和木质素，可通过纤维素羟基的衍生化反应引入具有特定吸附性能的官能团，提高对重金属的吸附能力。通过化学改性获得的生物质吸附剂，具有良好的吸附性能，但固液分离困难。本项目拟采用碱化、醚化交联、接枝共聚等改性方法，向互花米草和加拿大一枝黄花中引入巯基、羧基、磺酸基、磷酸基等功能基团，获得一系列生物质吸附剂，再以它们为母体采用化学沉淀法制备易于固液分离的磁性生物质吸附剂。通过系统研究制备过程中的关键影响因素，揭示磁性生物质吸附剂的制备机理。以模拟的重金属污染水为研究对象，系统评价磁性生物质吸附剂对水体中典型重金属的吸附、解吸特性，并进一步探讨其作用机制，阐述吸附剂表面的饱和磁强和功能性官能团的富集机制，构建功能性官能团与重金属吸附效能的构效关系，从而为推动磁性生物质吸附剂的实际应用提供理论依据和技术支持。

随着现代工业的迅速发展，水体重金属污染已成为我国最主要的环境问题之一。吸附法是去除水体中重金属的主流技术之一，如何获得高性能、低成本的吸附剂、实现吸附剂回收与再生是吸附法的关键。本项目采用碱化、醚化交联、接枝共聚等改性方法，向互花米草和加拿大一枝黄花中引入磺酸基、巯基、磷酸基、羧基等功能基团，再以它们为母体采用化学沉淀法制备易于固液分离的磁性生物质吸附剂，并用于水环境中重金属离子的吸附去除。结果表明，改性温度、改性剂投加量、催化剂浓度、原料配比、改性时间、碱性等因素对吸附剂的吸附性能有影响，但不同功能基团的吸附剂影响因子和影响程度均有差异性。与未改性前的原料相比，改性后的吸附剂表面变得疏松多孔，FTIR和XPS分析证明不同的功能基团被成功接枝到互花米草上；XRD分析表明改性后的吸附剂与Fe3O4成功结合，反应过程中没有破坏其晶体结构；磁滞回线和磁响应性分析表明，磁性生物质基吸附剂的饱和磁化强度相对Fe3O4有所降低，但仍具有较好的磁响应性，可以在外加磁场中实现快速的固液分离。磁性生物质基吸附剂对水中Cu(II)、Cd(II)和Hg(II)具有良好的去除效果，其对重金属离子的吸附是自发的吸热反应过程，吸附过程以化学吸附为主，引入的功能基团参与了吸附反应。在动态吸附过程中，增大柱高、减小过柱流速和浓度，可以延长穿透时间，提高重金属离子的去除率，同时通过盐酸洗脱可以实现填充柱的再生。上述研究结果表明，磁性生物质基吸附剂既能实现水中重金属离子的有效去除，又能实现吸附剂的回收、再生与循环利用。