聚合物基纳米氧化铁对污水中磷的选择性吸附分离及作用机理

Phosphorus from municipal sewage is one of the major nutrients responsible for eutrophication. While phosphate ores are expected to be depleted in the near future. Hence it's of great importance to remove and recover the phosphorous by adsorption technology. Polymer-based nanosized ferric oxides exhibit high adsorption capacity and recovery ability for phosphate, and good reusability as well. However, the contributions of pore and chemical structures to the adsorption selectivity are still unclear. To investigate the underlying mechanism of selective adsorption, several advanced technologies such as SPR, ITC, FT-IR, RAMAN, SEM-EDS and TEM, are utilized in combination with traditional adsorption methods. First, it's investigated about the dependence of adsorption capacity and selectivity on adsorbents components, their chemical structures, specific area, pore structure as well as environmental conditions. Subsequently, the interactions sites and mode between nanosized ferric oxides and phosphate are explored, followed by revealing the synergistic reaction between polymeric matrix and nanoparticles during the adsorption process. Finally, the adsorption/desorption mechanism of phosphate on polymer-based nanocomposite are revealed. Based on those results, the structure of the polymer-based composites could be optimized, and a systematic mechanism research method for adsorption would be established. This work would provide theoretical basis for the development of highly selective, specific and reusable polymer based nano-absorption materials.

目前世界各国普遍面临磷资源匮乏问题；同时，磷是引起水体富营养化的关键原因。聚合物基纳米氧化铁对污水中磷酸根有优异的吸附分离和回收能力；但其孔结构和化学结构对吸附选择性的影响机制尚未探明。本项目采用表面等离子共振技术（SPR）、等温微量热滴定法(ITC)、红外光谱（FT-IR）、激光拉曼光谱（RAMAN）、扫描电镜-X射线能谱仪(SEM-EDS)及透射电镜（TEM）等弱相互作用原位研究手段与吸附法相结合的方式，探讨聚合物基纳米氧化铁的化学组成、比表面积、载体孔结构及外界环境对磷酸根吸附选择性的影响；揭示纳米氧化铁与磷酸根的相互作用机理，纳米氧化铁与聚合物载体的协同作用机制，以及磷酸根在吸附材料表面的吸附分离机制；在此基础上优化吸附材料结构，建立吸附机理系统研究方法。本项目研究成果为开发出对污水中磷酸根具有高选择性、专一性、可再生的聚合物基纳米吸附材料提供理论依据。

目前世界各国普遍面临磷资源匮乏问题；同时，磷是引起水体富营养化的关键原因。聚合物基纳米氧化铁对污水中磷酸根有优异的吸附分离和回收能力；但其孔结构和化学结构对吸附选择性的影响机制尚未探明。本项目采用原位沉淀法，通过在表面含有季铵基团的阴离子交换树脂上负载不同含量的纳米氧化铁，制备出具有快速吸附能力、高选择性、高回收率的聚合物基纳米氧化铁吸附材料。采用拉曼光谱（RAMAN）、红外光谱（FTIR）、扫描电镜（SEM）等弱相互作用原位研究手段与吸附动力学和热力学相结合的方式，探讨聚合物基纳米氧化铁对磷酸根选择性吸附的作用机理。研究结果表明，吸附亲和力受化学协同作用控制，其中聚合物基体表面季铵基团提供离子交换或静电作用位点，负载的纳米氧化铁表面羟基提供配位作用位点，多种作用协同产生了吸附驱动力，且纳米粒子的存在有利于增大吸附比表面积，进一步提高吸附容量和选择性。吸附过程可用准二级动力学模型和Freundlich等温吸附模型予以描述，吸附速率与聚合物基体表面Donnan膜预富集效应和多孔结构对磷酸根渗透扩散速率有关。本项目机理研究结果可以为开发高选择性、专一性、可再生的聚合物基纳米吸附材料提供理论依据。