电位响应型超亲和性重金属离子交换磁性纳米材料的制备与介尺度耦合传质机制

For low-cost, efficient and continuous separation and recovery of trace heavy metal ions from waste water using electrically switched ion exchange (ESIX) technique, a novel combination process composed of a fluidized bed and an electromagnetic coupling regeneration system with an ESIX magnetic nanomaterial for the wastewater treatment was proposed. It will be the key issue to develop an ESIX magnetic nanomaterial with superaffinity for trace heavy metal ions in this study. Herein, the novel ESIX magnetic nanomaterial will be fabricated by coating co-polymer composites of porphyrin (or Cyclen) and aniline (or pyrrole) with high ion selectivity on magnetic nanomaterials. The microstructure with ion-exchange functional units will be designed based on the special binding forces acting between the target heavy metal ion and organic ligands. The affinity and selectivity of the obtained materials will be improved by tuning the target ionic ligand and creating novel polymerization technique. Furthermore, the ion exchange capacity and affinity of the obtained materials will be enhanced by modulating the ion vacancy density via tuning the electric potential gradient of the obtained material. As a result, the trace heavy metal ions in the wastewater are expected to be selectively separated and recovered by the affinity adsorption and ESIX regeneration with potential-triggered proton self-exchange effects. In this proposal, the principle for precise fabrication of ion exchange unit, the mechanism of ESIX heavy metal ions, the interface charge and ion transfer phenomena, and the mesoscale coupling mass transfer mechanism in the molecule/particle/flow-field multi-scale system will be mainly investigated and an effective dynamic model will be constructed. The obtained know-how is expected to be a theoretical basis for the industrial application of such a novel wastewater treatment process.

为实现经济、高效、连续的电控分离回收废水中的痕量毒性重金属离子，提出了将电控离子交换磁性纳米材料用于流化床-电磁耦合再生系统的处理废水新工艺，该工艺关键是制备出电位响应型超亲和性重金属离子交换磁性纳米材料。本项目以磁性材料表面包覆有苯胺(吡咯)与卟啉(或大环多胺)共聚的导电聚合物体系为研究对象，基于具有生物功能的有机配体与目标离子的相互作用特点设计离子交换基元的结构，采用目标离子作为双功能配离子结合聚合工艺条件对材料的微结构进行精密调控和优化来提高亲和性和选择性。通过调变电位梯度控制离子空位密度来增强材料亲和性和离子交换容量，并组合亲和吸附与电位响应质子自交换效应驱动重金属离子释放单元操作来实现目标离子的选择性连续分离。重点研究离子交换基元微结构的精密构筑原理、电控分离机制、界面电荷与离子传递、颗粒两侧介尺度耦合传质机制，并构建有效的动力学模型，为该处理废水新工艺的工业应用提供理论依据。

传统离子型废水处理技术主要包括化学共沉淀法、离子交换法和生物处理技术等。这些技术始终存在处理能力低、处理速率慢和易产生二次污染等缺点，已无法适应当前社会对废水处理技术的要求。为克服传统离子型废水处理技术的缺点，打破技术瓶颈，实现废水中目标离子的高效、连续、无污染电控分离，本课题设计开发了一种新型流化床-电磁耦合再生系统，并通过将电活性离子交换功能材料均匀包覆在磁性纳米颗粒表面，制备了一系列对目标离子具有超亲和力和优良选择性的电位响应型离子交换磁性纳米功能材料。同时，基于材料表面的离子交换亲和性位点与目标离子之间相互作用力的特点，通过调控制备方法和条件提高了材料的离子交换容量和上载速率，并采用电位梯度控制等手段优化了材料的电位再生效率。通过原位电化学测试技术和先进材料表征方法研究了电位响应型离子交换磁性纳米功能材料的离子交换微元结构的精密构筑原理、目标离子的上载和电控再生机制并构建了离子上载动力学模型。结果表明，电位响应型离子交换磁性纳米功能材料对废水中的目标离子展示出了高选择性和强亲和性，并且对目标离子的捕获速率和离子交换容量远超其他材料。此外，通过外加磁场可实现电位响应型离子交换磁性纳米功能材料的高效回收，同时控制施加在材料回收电极上的电位即可使材料捕获的目标离子得到释放且材料得到再生，整个目标离子分过程快捷、高效、无二次污染。在连续循环的离子分离过程中，电控离子交换磁性纳米材料始终保持稳定的离子交换容量与极高的材料再生效率，证明了材料卓越的循环稳定性和电化学可再生性。电控离子交换磁性纳米材料用于流化床-电磁耦合再生系统废水处理新工艺提升了离子型废水的处理效果和处理速率，实现了废水中目标离子的快速选择性连续分离和处理过程零二次污染，该技术有望在水处理领域得到广泛应用，实现水处理技术的全面革新。