磁性Fe3S4固液微界面诱导有机胂氧化还原机制研究

The organoarsenic compounds are easily converted into highly toxic organic/inorganic arsenic species by the soil minerals and microorganisms, which have attracted much attention in the environmental safety. Iron sulfides, as one of the most abundant minerals in water, sediments and soils, have been widely participated in the environmental pollutants transformation. And the interface properties of iron sulfides play important roles in the adsorption and redox of pollutant molecules. However, few researchers focus on the organoarsenic transformation mechanism with iron sulfides. In the previous study, we interestingly found that the organoarsenic transformation mechanism with the magnetic Fe3S4 depend on the solution pH. In this project, the mechanism of electron transformation and active species generation induced by the solid-liquid micro-interfaces of magnetic Fe3S4 are systematically studied by the surface analysis technologies. The organoarsenic transformation mechanisms are investigated by the combination of intermediate products analysis and theoretical calculation. After that, the synergistic effects of different active species on the organoarsenic transformation are also clarified by the captures experiments and ESR analysis. Base on these results, the effects of environmental factors on the organoarsenic transformation with the magnetic Fe3S4 were further discussed. This study can deepen our understanding on the organoarsenic transformation mechanism induced by the iron sulfides and the cycling process of iron, sulfur, carbon, arsenic, oxygen and other elements in the natural environment.

有机胂经禽畜代谢后进入环境介质中并转化为高毒性的有机及无机砷物种，其环境安全性日益引发关注。硫铁矿作为水体、沉积物及土壤中典型还原性铁矿物，广泛参与环境污染物的转化，且其固液微界面环境对污染物分子的吸附及氧化还原起到重要作用。然而，有机胂在硫铁矿界面转化的研究却鲜有报道。申请者在前期研究中发现有机胂与磁性Fe3S4作用时，其转化产物及机制依赖于体系pH。本项目拟系统研究磁性Fe3S4固液微界面电子转移及其诱导活性物种生成机制；通过中间产物分析与理论计算探究有机胂分子结构稳定性及转化特性；揭示有机胂在磁性Fe3S4固液微界面转化过程中不同活性物种间的协同作用机制。在理解磁性Fe3S4固液微界面诱导有机胂转化过程基础上，进一步讨论环境因子对有机胂在磁性Fe3S4固液微界面转化过程的影响，为深入认识有机胂类污染物在硫铁矿界面转化过程以及铁、硫、碳、砷、氧等元素在自然界中循环特征提供参考。

有机胂与铁矿物的相互作用是其非生物转化的一种重要途径，且矿物固液微界面环境对有机胂的吸附及氧化还原起着关键作用。本项目利用多种方法合成出高纯的磁性Fe3S4，优化溶剂类型及比例，调控Fe3S4表面结构。分析磁性Fe3S4固液微界面活性物种的种类、浓度及其生成机制；考察溶氧量、pH、共存离子、天然腐殖质等对磁性Fe3S4固液微界面性质、活性物种生成机制、有机胂转化机理的影响。研究结果表明，磁性Fe3S4结构中的S(-II)可直接提供电子，并诱导洛克沙胂中的硝基向氨基转化，且其还原效率随着溶液pH的降低而增加。而在中性及弱碱性条件下，洛克沙胂仅吸附于磁性Fe3S4表面。此外，Fe3S4表面硫空位使其表面含有不饱和配位的Fe(II)及Fe(IV)等活性铁物种，从而提高其对O2和H2O2等小分子的活化效率并生成具有强氧化性的•OH，进而实现洛克沙胂的氧化及亚砷酸根的氧化。基于此，本项目阐明了磁性Fe3S4固液微界面铁、硫等元素循环机制及其对活性物种生成的作用及贡献，以及有机胂转化过程对反应气氛、活性物种的依赖特性。