Institute for Environmental Sciences, University of Shizuoka , 52-1 Yada, Suruga-ku, Shizuoka 422-8526, Japan.
Environ Sci Technol. 2013 Sep 3;47(17):9660-7. doi: 10.1021/es4010398. Epub 2013 Aug 19.
In this study, we investigated the behavior of Sb(V) during the transformation of poorly crystalline Fe(III) oxyhydroxides (two-line ferrihydrite) with various Sb/Fe molar ratios at pH 6.0. Both XRD and Fe EXAFS analyses confirmed that goethite and hematite are the primary transformation products of the ferrihydrite in the presence of Sb(V). The crystallization kinetics showed that the transformation rate with Sb(V) was approximately the same as that of the control (without Sb(V)), which indicates that the presence of Sb(V) does not influence the transformation rate to a noticeable extent. Throughout the transformation, Sb(V) dominantly partitioned in the solid phase and no desorption of Sb(V) was observed. Furthermore, Sb EXAFS analyses suggested that Sb(V) in the solid phase is structurally incorporated into crystalline goethite and/or hematite generated by the ferrihydrite transformation. Hence, Sb(V) transfers into the thermodynamically stable solids from the metastable ferrihydrite with aging, indicating a rigid immobilization of Sb(V). These findings are valuable for making predictions on the long-term fate of Sb associated with ferrihydrite in natural environments.
在这项研究中，我们研究了在 pH 值为 6.0 时，不同 Sb/Fe 摩尔比的 Sb(V)在转化为结晶不良的 Fe(III)氢氧化物（两线水铁矿）过程中的行为。XRD 和 Fe EXAFS 分析均证实，在 Sb(V)存在的情况下，针铁矿和赤铁矿是水铁矿的主要转化产物。结晶动力学表明，含 Sb(V)的转化速率与对照（不含 Sb(V)）几乎相同，这表明 Sb(V)的存在并没有显著影响转化速率。在整个转化过程中，Sb(V)主要分配在固相，没有观察到 Sb(V)的解吸。此外，Sb EXAFS 分析表明，固相中的 Sb(V)是通过水铁矿转化生成的结晶针铁矿和/或赤铁矿结构上掺入的。因此，Sb(V)随着老化从亚稳态的水铁矿转移到热力学稳定的固体中，表明 Sb(V)的固定性很强。这些发现对于预测 Sb 与自然环境中不稳定水铁矿相关的长期归宿具有重要意义。
