典型纳微米颗粒对水铁矿表面反应性及相转变过程的影响

Nowadays, nanogeoscience is rapidly developing, and the mineral characteristics, the geochemical behaviors, and the environmental functionality of nanominerals have drawn great concerns in nanogeoscience area. Ferrihydrite is a typical nanomineral and is ubiquitous at earth’s near-surface environment. It shows high reactivity and can be easily transferred into other mineral phases because of its weak crystallinity. Considering the complex interactions between nanoparticles, this project intends to study the effect of several nano-/microparticles, including montmorillonite, carbon nanoparticles, and TiO2 nanoparticles, on the microstructure, reactivity, and transformation of ferrihydrite, and the related mechanisms will be further discussed. In this project, we will combine batch experiments (e.g., adsorption and catalysis experiments) with instrumental characterizations (e.g., microscopic and spectral techniques), to first study the effects of the selected nano-/microparticles on the structure and morphology of ferrihydrite. Then, we will focus on how the selected nano-/microparticles affect the adsorptive behavior and the catalysis activities of ferrihydrite. After that, the effect of nano-/microparticles on the transformation pathway of ferrihydrite (to goethite or hematite) will be further explored, and the controlling factors to the transformation process will be studied as well. Based on the obtained results, we intend to establish the correlation of structure of nano-/microparticles – the aggregation form of ferrihydrite – the transformation pathway of ferrihydrite, and try to understand how the migration of electrons from nano-/microparticles to ferrihydrite can affect the reactivity and phase transformation of ferrihydrite. The expected outcomes of this project may provide valuable information for clarifying the mineral characteristics, the geochemical behaviors, and the environmental functionality of ferrihydrite at earth’s near-surface.

当前，纳米地球科学快速发展，纳米矿物的各种矿物特征、地球化学行为和环境功能属性是纳米地球科学领域的研究热点。水铁矿是一类广泛分布于地表环境的纳米矿物，具有反应活性强、易相转化的特征。项目从纳米物质的复合效应出发，提出研究地表环境中常见纳微米颗粒（蒙脱石、碳纳米颗粒、纳米TiO2）对水铁矿微观结构、表面反应活性、相转化过程的影响及相关机制。将宏观反应活性测试与现代谱学分析、微束微区探测技术相结合，从研究纳微米颗粒对水铁矿微观结构影响入手，重点考察纳微米颗粒如何影响水铁矿的表面吸附和催化活性及相关机制，研究纳微米颗粒对水铁矿相转化过程的影响及主要控制因素。在此基础上，建立纳微米颗粒结构—水铁矿聚集状态—相转化过程的对应关系，揭示纳微米颗粒如何通过电子转移改变水铁矿的反应活性和相转化过程。项目预期结果可为系统阐明水铁矿的矿物特征、地球化学行为和环境功能属性提供重要信息。

纳米矿物的结构特征、地球化学行为、环境功能属性等是当前矿物学领域的研究热点。水铁矿是一类广泛分布于地表环境的纳米矿物，具有反应活性强、易相转化的特征。项目从纳米物质的复合效应出发，拟研究地表环境中常见纳微米颗粒对水铁矿微观结构、表面反应活性、相转化过程的影响及相关机制。从考察纳微米颗粒对水铁矿微观结构影响入手，重点研究纳微米颗粒如何影响水铁矿的表面吸附和催化活性及相关机制，探究纳微米颗粒对水铁矿相转化过程的影响及主要控制因素；在此基础上，建立纳微米颗粒结构—水铁矿聚集状态—相转化过程的对应关系，揭示纳微米颗粒如何通过电子转移改变水铁矿的反应活性和相转化过程。. 研究工作取得了一些创新成果：（1）环境中碳纳米颗粒、黏土矿物、二氧化钛等纳米颗粒可以通过静电作用、化学键合、物理分散等与水铁矿作用，改变水铁矿的聚集状态及反应活性；（2）揭示了水铁矿表面协同吸附富集阴-阳离子的作用机制，并进一步研制了多种具有核壳结构的高效能磁性吸附材料，能吸附去除水/土壤中的阴离子/阳离子；（3）发现碳纳米材料能通过改变水铁矿氧化还原电位、增强电子传导能力等作用，增强水铁矿的催化反应活性，并构建了多种高效异相芬顿催化剂；（4）发现碳纳米颗粒和黏土矿物可以通过改变水铁矿的聚集状态而改变其相转变速率、产物等，而纳米二氧化钛的光生电子注入能加速水铁矿向赤铁矿转变。上述研究工作不仅证实了环境中纳米矿物之间存在复杂的复合效应，还为系统阐明水铁矿的反应活性及相变特征提供了新信息，并进一步设计了多种新型纳米矿物污染控制材料，实现了从水铁矿反应活性的基础理论研究到新功能材料设计的应用研究的耦合。