海藻基微米结构碳球的可控制备及动态吸附研究

Efficient treatment of heavy metal-containing wastewater is not only a hot topic in the field of chemical engineering but also a global issue for the construction of environmental-friendly society. In contrast to other techniques for the this issue, adsorption removal processes have been paid particular attention, owing to the unique features that free of secondary pollutants, easy-to-conduct and avoiding use of costly equipments; however, the designing of high-performance adsorptive materials are of key importance to fully take advantages of this technique. Further, it should be noted that, even though the utilization of renewable biomass to fabricate sorbents has been achieved significant progress recently, the construction of high-performance monolithic carbon beads with controllable ion-diffusion paths and interfacial characteristics remains a challenging task. In this project, we plan to prepare monolithic carbon beads with multiple porosity and tailored interfaces by combinatorial treatment of preformed hydrogel composite, which was prepared via a hierarchical assembly of alginate molecules assisted by dual templating function of Ca2+ ions and nano CaCO3, using freeze drying, carbonization, calcium species removal and PDA surface modification. The evolution and changes of porosity, surface chemistry and mechanical stability on the preparative parameters will be thoroughly investigated by using various characterization techniques. In parallel, we plan to investigate the crucial factors that affect the dynamic adsorption performance and correlate the experimental data with typical models. Finally, the potential relationship between adsorption performance and structural properties and interfacial characteristics will be established. This project would provide theoretical support for the designing of related functional materials using alginate-based substances.

水体中重金属离子的控制与处理是当前化学化工领域的热点研究方向，也是建设环境友好型社会的重要课题。吸附去除过程因无二次污染、简单易操作等优势特点受到广泛关注，但高性能吸附材料的结构设计与界面控制及液固高效分离是关键。利用生物质资源制备功能性吸附材料已取得较大进展，然而创制离子通道与界面特性可控的高性能整体碳基材料仍是科学难题。本课题基于海藻酸钠易于调控的胶凝过程及成球机制特点，拟借助原位钙离子和纳米碳酸钙双重模板机制多级组装复合凝胶微球，通过冷冻干燥、高温碳化、模板去除及聚多巴胺表面修饰等技术融合制备多阶孔道的微米级碳球。研究多级组装过程、冷冻干燥技术、碳化工艺及聚多巴胺沉积方式对孔道结构与表面化学及机械稳定性的调控作用与规律，探究铬离子动态吸附过程行为的关键影响因素及吸附模型与机制，揭示离子通道及表面特性调控与材料吸附性能的构效关系，实现碳基功能材料规模化制备，丰富藻类资源的开发利用技术。

随着工业的快速发展，水污染成为人类面临的严肃课题，尤其是重金属污染对人体的危害极大，因此开发有效的吸附剂去除水体污染具有重要的现实意义。本项目以水体中的重金属六价铬离子污染为例，利用海藻酸钠和铁盐作为前驱体通过高温处理制备了不同宏观结构的磁性多孔碳吸附剂，采用批量吸附实验证明所制备的材料对水体中铬离子具有良好的去除效果。通过对比实验，发现制备的整体式吸附剂具有更广阔的应用前景。海藻酸钠等生物质在惰性气体(如氮气)保护下，经过高温处理会形成生物碳，铁盐经过碳热还原能够形成磁性纳米材料，结合上述两种特性，采用铁离子对海藻酸钠进行交联进而高温碳化制备具有多孔结构和特殊物化性质的磁性多孔碳生物吸附剂，能够用于水体中重金属离子的有效去除。. 首先制备了纳米级磁性吸附剂Fe-SA-X，研究了不同碳化温度对吸附剂性能的影响，结果表明Fe-SA-800的吸附效果优于Fe-SA-400和Fe-SA-600，说明温度越高，吸附效果越好。对影响吸附实验的参数进行详细考察，证明最佳吸附条件的pH值为2.0；动力学研究表明吸附过程更好地遵循拟二级模型，等温吸附实验数据更加符合Langmuir模型，说明是单分子层吸附，由分离因子RL在0到1之间，说明吸附是有利的，吸附剂对Cr(VI)的吸附不受温度的影响。研究了常见阴离子强度对吸附的影响，说明吸附是一种竞争机制，阴离子所带的负电荷数量越多，对Cr(VI)离子的去除影响越大。重复使用性表明材料可以循环使用，使用三次后其去除率依然保持在80%左右，证明其性能稳定，效果良好。. 利用Ca2+交联比Fe3+交联所得到的水凝胶球机械强度更大，采用高温处理干燥的Fe-Ca-SA凝胶球得到整体式磁性碳球吸附剂(MMCB)，其孔隙率增大，吸附量由原来的86.32mg/g提升到143.20mg/g。实验详细研究了各种参数对吸附效果的影响，实验数据更加符合拟二级动力学模型和Langmuir等温吸附模型，热力学研究(ΔH>0, ΔS>0, ΔG<0)表明MMCB对Cr(VI)的吸附是自发进行的，是吸热反应。对于吸附机理和循环使用性也进行了详细讨论。