基于生物电化学方法探究无机配体与铁氧化物影响U(VI)还原的热力学-动力学关系研究

The dissimilatory metal reducing bacteria (DMRB) can utilize the extracellular electron transfer process for the purpose of reducing U(VI) that present in the groundwater. Due to the importance of this U(VI) reduction process in controlling the fate and transport of uranium in groundwater, elucidating the impact of groundwater's environmental characteristics on hexavalent uranium reduction has become a pivotal research topic in the field of uranium pollution control. In this study, by using methodologies derived from the field of bioelectrochemical systems, we will investigate the impact of groundwater's environmental characteristics on U(VI) reduction from two facets, which are: (1) the effect of inorganic ligands, and (2) the effect of competing electron acceptors. We will establish the relationships among "U(VI) speciation - U(VI) redox potential - U(VI) reduction kinetics", "the reduction extent of competing electron acceptors - the redox potential of competing electron acceptors - the kinetics of U(VI) reduction". With the help of bioelectrochemical techniques, we will establish a new research method which study the uranium redox process in groundwater from thermodynamic perspectives. This focus of this study is on the groundwater's environmental characteristics on hexavalent uranium reduction, and the outcome of this research will further our understanding of the U(VI) fate and transport in groundwater, and will serve for the purpose of further optimize the U(VI) pollution control processes. Overall, this research has high scientific merits and potential application values.

异化金属还原菌（Dissimilatory Metal Reducing Bacteria, DMRB）能够利用其特有的胞外电子传递机制还原地下水中的U(VI)，进而影响铀在地下水中的迁移转化，而探究地下水环境因素对这一还原过程的影响已成为地下水铀污染控制领域的关键问题。针对这一关键问题，本研究引入生物电化学的研究方法，利用DMRB组成的生物阴极，从热力学角度揭示（1）无机配体和（2）铁氧化物对U(VI)还原速率的影响。通过研究，揭示“U(VI)形态-铀的还原程度-铀的氧化还原电位-U(VI)还原速率”的关系，“竞争受体还原程度-竞争受体氧化还原电位”的关系，形成以生物电化学方法为主导的，通过考察反应过程热力学变化，揭示环境因素对DMRB还原U(VI)的影响的研究思路。本研究立足于揭示地下水环境特征对U(VI)迁移转化的影响，研究成果将为优化铀污染控制技术提供科学依据。

六价铀是土壤和地下水中的常见重金属污染物，其环境化学行为受异化金属还原菌调控。本研究以Geobacter Sulfurreducens PCA为模式菌株，以TiO2为基地，构筑了光-电阴极，首先探究了异化金属还原菌在可见光照射下向金属电极转移电子的通路，发现Geobacter Sulfurreducens PCA位于胞外的cytochrome-c蛋白可在可见光照射下转化为激发态，并利用激发态蛋白进行胞外电子传递过程，该电子传递通路可促进浅滩、湿地等环境下金属异化还原菌向六价铀传递电子的能力。在应用层面，本研究开发了一种新型Cu-Ag电极，可在-1.0 V的低外加偏压下，同步还原处置硝酸盐和六价铀两种地下水污染物，该研究成果可为治理地浸采铀废水等提供技术支撑。