环境响应性核壳结构零价铁纳米复合粒子的设计、制备及降解地下水中三氯乙烯的行为与机理研究

The Nanoscale Zero-Valent Iron (NZVI) is easily form much larger flocs reunion and loss its reactivity, which is an urgent problem needed to be solved when NZVI is used for the groundwater remediation process and engineering. An innovative heterogeneous polymerization technology named (mini)emulsion polymerization will be used to prepare composite nanoparticle with good stability and amphiphilic, which is the core-shell composite nanonpaticle was prepared based on by polymer coated NZVI. The relation between preparation-dynamic rheological behaviors -micro-structure control of polymeric composite will be researched by torque rheometer and the optimal process parameters could be got, and the kinetic model of emulsion polymerization was derived. So the structure and morphology of composite nanocomposite could be controlled. Secondly, enrichment of the trichloroethylene(TCE) and controllable release of NZVI could be achieved with the response to environment stimulation of shell, which is got by the design of polymer monomers. The optimal reaction parameter could be got based on the experiments of affecting factor and simulation. Finally, the kinetic characteristics of the degradation of nanocomposite will be researched detailedly. Then the relativity between the degradation speed and the intermediates of contaminants with the chemic structure/property of the polymer will be researched to prove the degradation mechanism of nanocomposite. So, therotically and actual importantly, this project will enrich and develop the methods for the multi-function NZVI preparation and for the reaction process, furthermore, will serve as a basis for the groundwater remediation process and engineering.

纳米零价铁极易团聚失活，是运用于污染地下水原位修复中急待解决的问题。项目拟采用一种新的非均相聚合技术—细乳液聚合法制备以纳米零价铁为核、智能聚合物为壳的纳米复合粒子，使其具有良好的稳定性和表面双亲性。通过流变仪研究多相体系高分子复合材料制备-流变行为-微结构调控的关系，确定最佳聚合工艺参数,建立聚合动力学模型，实现纳米复合粒子结构和形貌的可控；然后通过对聚合物单体的分子设计，使壳层具有环境刺激的响应性，实现壳层对三氯乙烯的富集和对纳米零价铁的可控释放；并在影响因素实验及模拟实验的基础上，确定最佳反应参数。进一步重点研究纳米复合粒子的降解动力学特征，并深入研究降解速率和污染物降解中间产物与聚合物化学结构、性质的相关性，探明复合粒子的降解机理。项目的研究成果将丰富和发展多功能纳米零价铁的材料制备方法和反应过程的研究方法，为实际运用提供理论基础和技术支持，具有重要的理论价值和实际意义。

自从纳米零价铁成功合成以来，在环境污染治理中显示出巨大的发展潜力。但是纳米铁颗粒由于其高比表面能和本身具有的磁力相互作用，容易团聚；同时因为其极强的还原性，极易在空气中和水体中被氧化失活，很难长时间保存和应用。如何解决这主要的两大问题是目前研究的热点。.本项目主要研究内容包含以下几部分：.（1）微乳液体系制备核－壳型纳米零价铁颗粒，针对以三氯乙烯为代表的含氯有机烃，由于其非水相、低溶解性、环境毒害性大的特点，项目将油相、水相及表面活性剂按照一定配比形成微乳液体系，在其中进行液相还原反应，制备了油膜包覆的核壳型纳米铁颗粒，颗粒平均粒径为80～120nm,分散均匀，几乎没有团聚现象。该乳化纳米铁颗粒在pH值较低的条件下能快速有效的去除三氯乙烯，去除率达到83%。.同时制备了几种不同的环境友好性水溶性高分子（壳聚糖、羧甲基纤维素、聚乙烯吡咯烷酮、淀粉）包覆型纳米铁颗粒，比较了制备条件和不同的包覆剂对纳米铁颗粒分散性和稳定性的影响，通过对重金属和有机氯代烃的降解，探讨了对不同种类污染物的降解效果。.（2）乳化纳米铁和包覆型纳米铁虽然对污染物都能快速有效的降解，但是壳层材料对目标污染物的富集和响应效果不理想，并且纳米铁颗粒进入水体不易分离，会造成环境风险。因此为了进一步提高对污染物的富集，制备了大孔树脂负载纳米铁复合材料，不仅发挥了吸附与还原降解的协同效应，并且易于分离回收。.（3）针对有机污染物，进一步制备了三维石墨烯负载纳米铁复合材料。该泡沫具有质轻、疏松多孔的特点和强亲油性，与活性炭、大孔树脂制备的负载纳米铁复合材料相比较，三维石墨烯纳米铁复合材料显示出更大的孔面积和更强的吸附能力，特别由于其强烈的亲油性，对有机染料、有机污染物的吸附量明显比活性炭和高交联树脂的大得多，同时负载纳米铁的三维石墨烯泡沫极其容易回收利用，大大减少了纳米颗粒易流失进入环境的风险。