Phase evolution of the surface iron (hydr)oxides to the iron sulfide through anion exchange during sulfidation of zero valent iron
Phase evolution of the surface iron (hydr)oxides to the iron sulfide through anion exchange during sulfidation of zero valent iron
复制标题
零价铁硫化过程中表面铁（氢）氧化物通过阴离子交换相演变为硫化铁
DOI：
10.1016/j.jhazmat.2021.127486
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发表时间：
2022
影响因子：
13.6
通讯作者：
Chunhua Xu
中科院分区：
文献类型：
--
作者：
Fengmin Li;Yue Zhang;Boyang Tian;Zheng Zhou;Li Ye;Jesse C. Carozza;Wensheng Yan;Haixiang Han;Chunhua Xu
零价铁（ZVI）表面自然形成的铁（氢）氧化物长期以来被认为是钝化层和惰性相，在环境修复中会显著降低反应活性。虽然它似乎没有直接的好处，以保持这些钝化层，在这里，我们表明，这些阶段是必要的中间体，通过一个阴离子交换途径的硫化过程中的ZVI铁硫化物的转化。预形成的（氢）氧化物在老化时经历相演变，并且可以有效地捕获特定相，这可以通过不同表征技术的组合来证实，所述表征技术包括扫描电子显微镜（SEM）、X射线光电子能谱（XPS）、X射线粉末衍射（XRPD）和X射线吸收近边结构（XANES）光谱。有趣的是，硫化后，所得样品源自不同的（氢）氧化物表现出不同的活动中的Cr（VI）螯合。Fe K边和Fe L2，3边的XANES研究表明，硫化后Fe保持不变，表明硫化铁的生成是一种非氧化还原的阴离子交换反应途径，其中O2-阴离子直接被S2-取代。因此，母体（氢）氧化物的结构特征由形成的铁硫化物继承，这使得它们由于其不同的结构性质而表现不同。
The naturally-formed iron (hydr)oxides on the surface of zero valent iron (ZVI) have long been considered as passivation layer and inert phases which significantly reduce the reaction activities when they are employed in environmental remediation. Although it seems there are no direct benefits to keep these passivation layers, here, we show that such phases are necessary intermediates for the transformation to iron sulfides through an anion exchange pathway during sulfidation of ZVI. The pre-formed (hydr)oxides undergo a phase evolution upon aging and specific phases can be effectively trapped, which can be confirmed by a combination of different characterization techniques including scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), X-ray powder diffraction (XRPD), and X-ray absorption near edge structure (XANES) spectroscopy. Interestingly, after sulfidation, the resultant samples originated from different (hydr)oxides demonstrate different activities in the Cr(VI) sequestration. The XANES investigation of Fe K edge and Fe L2,3edge indicates Fe remains the same after sulfidation, suggesting a non-redox, anion exchange reaction pathway for the production of iron sulfides, where O2-anions are directly replaced with S2-. Consequently, the structural characteristics of the parent (hydr)oxides are inherited by the as-formed iron sulfides, which make them behave differently because of their different structural natures.