聚电解质纳米纤维可控负载零价铁/二氧化钛复合纳米颗粒消除典型水污染物的研究

In recent years, zerovalent iron nanoparticles (ZVI NPs) have received tremendous scientific and technological interest because of their superior capacity of environmental remediation. However, their potent reactivity with respect to water and oxygen, along with high specific surface area favors an easy oxidation and agglomeration and leads to the decrease of the activity during the process of contaminant degradation, thereby limiting their application in wastewater remediation. Titanium dioxide (TiO2) is another reagent often used for photocatalytic removal of organic pollutants in the environment because of the advantages of the low cost, high stability, non toxicity, and high photocatalytic activity. But, the high degree of recombination of electrons and holes lowers the photodegradation of TiO2. It is reported that metal substances can trap electrons and suppress the recombination of electrons and holes in TiO2, and simultaneously TiO2 can delay the formation of the surface oxide layer on ZVI NPs. Combining the advantage of metal-doped TiO2 nanocomposites and our previous fundamental study related to ZVI NP-immobilized nanofibrous mats in environmental remediaiton, we hypothesized that immobilizing ZVI/TiO2 NP onto the surface of nanofibers would be a efficient strategy to solve the problem of ZVI NPs in environmental remediation and to produce novel, functional wastewater remediation materials. In this project, electrospun poly(acrylic acid) (PAA)/poly(vinyl alcohol) (PVA) mixture was treated at an elevated temperature to render them water stable. Then, the water-insoluble nanofibrous mats were used as nanoreactors to complex ferric ion and assemble TiO2 nanoparticles for subsequent formation and immobilization of ZVI/TiO2 nanocomposites. By modulating the complexation/reduction cycles between ferric ion-PAA complex and NaBH4, and the alternative layer-by-layer self-assembling numbers of TiO2/PAA, ZVI/TiO2 nanocomposite-immobilized nanofiber with tunable nanoparticle content, size and distribution could be produced. Factors influencing the pollutant degradation capability of nanocomposite fibrous mats, pollutant degradation rate, and kinetics were systematically investigated. The concrete photocatalytic oxydation/reduction synergetic degradation mechanism was analyzed. Findings from this study provide a foundation for further rational design of functional composite nanofibrous materials for environmental remediation.

解决零价纳米铁颗粒在废水处理中易于团聚、表面易钝化和分散在水体中形成二次污染问题是目前国内外研究的难题和热点，本课题针对上述三大问题，利用二氧化钛在污染物处理方面的优势，结合金属掺杂理论和申请人的前期研究基础，提出以静电纺聚电解质纳米纤维为反应载体，利用聚电解质的羧基官能团能络合铁离子以及表面电负性特点，通过原位络合/还原和静电层层自组装技术将零价铁/二氧化钛复合纳米颗粒固定在纳米纤维上，设计出新型的光催化氧化/还原双功能协同的废水修复复合纳米材料。研究制备过程中的关键技术和难点问题，构筑出零价铁/二氧化钛含量、粒径大小和分布可调的复合纳米纤维毡。探讨复合纳米材料与污染物作用的构效关系；建立降解速率、动力学模型；阐明纳米纤维界面微环境下，零价铁/二氧化钛复合纳米颗粒对污染物的光催化氧化/还原协同降解机理，对零价铁系废水净化材料的应用具有重要意义，为功能性废水净化滤材的开发奠定基础。

解决零价纳米铁颗粒在废水处理中易于团聚、表面易钝化和分散在水体中形成二次污染是目前国内外研究的难题和热点。本项目针对上述问题，利用二氧化钛在污染物处理方面的优势，结合金属掺杂理论，以静电纺聚电解质纳米纤维为反应载体，利用聚电解质的羧基官能团能络合铁离子及表面带电负性的特点，通过原位络合/还原和静电层层自组装技术将零价铁/二氧化钛复合纳米颗粒成功地固定在纳米纤维上，制备了新型的光催化氧化/还原双功能协同的废水修复复合纳米材料。复合纳米纤维能快速、高效的去除模拟印染废水中的品红、灿烂绿以及亚甲基蓝染料，60 min钟内对染料的去除效率均能达到95%，且具有良好再生性能，对零价铁系废水净化材料的应用具有重要意义，为功能性废水净化滤材的开发奠定了基础。