好氧体系硫化零价铁界面动态交互机制研究与模型构建

The passivation of iron oxide can reduce the reaction activity of zero valent iron (ZVI), sulfidation could be an effective strategy to tune the reactive properties of ZVI in favor of a broad range of contaminant removal processes, the existence of O2 in the aerobic system makes the reaction mechanism of sulfidation zero valent iron (S-ZVI) with the contaminants more complicated. The effect and mechanism of S-ZVI to contaminants are different due to different preparation methods and different pollutants. In this study, S-ZVI was prepared by different preparation methods and the effect of preparation on the surface morphology and characteristics of S-ZVI was also evaluated. The kinetics of organics and heavy metal pollutants removal using S-ZVI by different preparation methods were studied under the aerobic system and different oxygen concentrations. FeS may directly affect the corrosion of ZVI, and subsequently affect the production of Fe(II). The differences in the mechanism of different pollutants removal were also studied. By analyzing the morphology, structure, composition, surface area and surface roughness of S-ZVI, the mechanism of reaction acceleration is revealed from the micro aspects. The binary time series correlation analysis of C/C0, Fe(II), Eh, DO and pH were plotted to identify and distinguish the dominant controlling processes for contaminant removal. The role of FeS and regeneration of Fe(II) were also evaluated from this correlation analysis. Electrochemical test were designed to illustrate the electron transfer rate and electron acceleration transfer mechanism. The conceptual and quantitative models will be built which will explain the effects of sulfidation on the improvements of ZVI reactivity in aerobic environment. It can also predict the active sites on the surface of ZVI, reaction kinetics and the change of characteristic parameters and provides the theoretical foundation for mechanism.

铁氧化物的钝化作用会降低零价铁（ZVI）的反应活性，ZVI表面修饰一定的硫化物可以显著提高其对污染物的去除率，好氧体系中O2使硫化零价铁（S-ZVI）反应机理变得更加复杂。S-ZVI因制备方法、污染物种类不同其影响和作用机制也不相同。本研究以不同的方法制备S-ZVI，研究制备方法对S-ZVI表面形貌及特征的影响；研究氧气及不同浓度对不同制备方法制备的S-ZVI去除有机物及重金属污染物的动力学变化，FeS对ZVI的腐蚀促进以及固液界面Fe(II)释放规律，研究不同S-ZVI去除不同污染物机理的差异。通过对材料形貌、结构、组成、比表面积、表面粗糙度等分析，从微观层面揭示反应加速机理；通过对C/C0，Fe(II)，Eh，DO以及pH等各参数时间序列相关性矩阵分析研究污染物去除机理。通过电化学手段研究硫化物对电子传递机制的影响。构建污染物去除动力学变化、表面反应活性位变化、DO变化模型。

本课题通过对零价铁（ZVI）进行硫化，以不同方法制备硫化零价铁（S-ZVI）。研究了制备方法对S-ZVI表面形貌及特征的影响，探索了S-ZVI去除有机物及重金属的动力学变化、FeS对ZVI的腐蚀促进及固液界面Fe(II)释放规律，分析制备方法和制备条件对去除动力学及界面作用机制的影响，揭示了污染物的机理，构建S-ZVI去除污染物的动力学模型。研究结果表明，Na2S、NaS2O4、Na2S2O3三种硫源制备的S-ZVI在结构、组分及性能上存在较大差异，Na2S为硫源制备的S-ZVI对Cr(VI)的去除效果最好。S-ZVI的表面由铁硫化物和铁氧化物组成，材料硫化的机理不随硫铁比改变而改变，S均匀地分布在材料内部，说明硫化过程向材料内部发生了扩散，不是普遍认为的核壳结构。硫化时间对S-ZVI性能有较大的影响，24 h时材料的性能达到最佳，制备体系的pH值也会影响S元素和ZVI之间的反应速率，pH为6时最佳。Fe(II)是还原去除Cr(VI)的主要电子供体，在pH为5时，Fe(II)的再生在Cr(VI)还原过程中起着重要作用，此时Fe(III)和Fe(0)反应产生的Fe(II)的再生率和利用率最高。氧气能够有效的促进ZVI的腐蚀以及提供电子供体，进一步释放Fe(II)。Cr(VI)去除过程反应速率常数随氧气浓度的增大而增大，当氧气浓度由0%增大到50%时，Cr(VI)去除效率由30%提升到100%。构建的溶解氧驱动钝化模型对于ZVI在不同条件下去除橙黄I的数据具有普适性，模型拟合数据和原始数据的吻合程度非常好。本课题创新性地研究了不同制备方法改性硫化铁去除污染物在好氧反应体系中的界面动态交互机制，构建了好氧体系中适用于S-ZVI去除污染物的普适性模型，对于丰富和进一步了解S-ZVI在水环境中的应用具有重要的指导价值。