沉积物中基于无机/有机导体的三维导电网络的结构特征及其导电机理

Biological current recently discovered will be an effective way for the in-situ remediation of sediments. Biological current is produced by the electrons generated by the microorganisms in the sediments and further transferred by the organic and inorganic conductors, which thus connects biochemical process between the separated spaces. The transfer characteristic of biological current in the sediments is closely related to the conductivity of the three-dimensional network in the sediments, but it is unclear for the generation of biological current as well as the electron transfer mechanism. In view of the research for the filled conductive polymer in the materials sciences, a new method is proposed in this application project, which is to model and construct a conductive system consisting of inorganic nanoconductors (e.g. iron compound conductors) and organic nanoconductors. Based on cross applications of conductor materials science, electrical circuits and water environment science, the research of this project is mainly on the interactions among inorganic nanoconductors and organic nanoconductors within the three-dimensional conductive network, the key factors influencing the electron transfer characteristics of the three-dimensional network and its conduction mechanism. Through these studies can elucidate the electron transfer mechanism of three-dimensional conductive network in the sediments and provides a theoretical basis for the regulation of the biological current in the sediments. The project research will strengthen to understand of the circulation process for elements in the sediments, and it has important guiding significance to develop new technique and technology for the in-situ sediment remediation.

新近发现的生物电流为水体沉积物污染原位修复提供了一条有效的途径。沉积物生物电流是微生物通过沉积物中无机和/或有机导体传递自身产生电子，从而将空间上分隔的生化过程串联起来的过程。沉积物中生物电流传输特性和其三维网络的导电体系密切相关，目前对于沉积物生物电流产生及电子传输机理还不清楚。本项目依据填充型导电聚合物材料的相关研究基础，提出了一种模拟构建在非导电基体间由无机纳米导体（铁化合物导体）和有机纳米导体组成沉积物导电体系的新方法。通过导体材料学、电子电路学、水环境科学交叉应用，本申请主要研究三维导电网络中无机纳米导体与有机纳米导体的相互作用关系、三维网络体系电子传输特性的关键影响因素及三维网络体系的导电机制，进而阐明沉积物中三维导电网络体系的电子传输机理。本项目将为沉积物生物电流调控提供理论依据，有助于强化对沉积物元素循环过程的认识，对于开发沉积物污染原位修复的新技术与工艺具有重要指导意义。

沉积物中存在着由生物电流耦合的空间上分离的氧化还原反应，这种生物电流的传导机制与沉积物中复杂的微生物与矿物质之间所形成的无机/有机导电网络具有密切的关系。因此，沉积物中的导电网络对促进污染物分解、驱动元素循环起着重要作用。研究和分析导电网络的结构及导电机理可以补充和扩展人们对沉积物中长距离电子传输机制的科学认识，为沉积物的修复提供新的解决思路和科学参考。.本项目基于复合材料结构导电特性构建了沉积物中的三维导电网络，并在渗流理论、电子隧穿理论及电网络等理论基础上研究了沉积物中三维导电网络导电规律及电导率的影响因素。研究结果表明沉积物中无机三维导电网络的导电特性中，大尺寸的基底颗粒更有利于导电颗粒间形成导电通道；而小尺寸的导电颗粒则可以使体系获得更低的渗流阈值和更高的电导率，Fe3O4粒径从1μm 减小到20nm，渗流阈值相应地从25.64%下降到17.01%，最大电导率从8.9×10-5 S/m升至5.3×10-3 S/m。以FeS2为导电填料的复合体系电导率明显高于以Fe3O4颗粒填充的复合体系。对于有机三维导电网络的电导规律和电导率的影响因素，有机复合材料中基底的尺寸效应被削弱，PPy/ SiO2复合材料的电导率在7.1%的填料体积分数下发生渗流，电导率最高可达45.2 S/m，增幅远大于Fe3O4/ SiO2复合体系。大长径比的纳米线因其跨空间连接优势，其发生电导率突跃所需的填料含量更小，并且基底颗粒及导电颗粒的尺寸效应被削弱。对于沉积物中三维无机/有机导电网络的导电特性研究表明了无机/有机导电材料间的协同作用。在Fe3O4中引入PPy纳米线，复合材料的渗流阈值从17.01%降至10.8%，电导率从1.2×10-3 S/m升至16.3 S/m，纳米线在颗粒填料中起到“桥梁”作用，两种填料间的相互作用不仅有效避免了同种材料间的团聚现象，也为形成导电网络提供了更加多样的连通方式。