Early Stage Formation of Iron Oxyhydroxides during Neutralization of Simulated Acid Mine Drainage Solutions
Early Stage Formation of Iron Oxyhydroxides during Neutralization of Simulated Acid Mine Drainage Solutions
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DOI：
10.1021/es301268g
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发表时间：
2012-08-07
影响因子：
11.4
通讯作者：
Waychunas, Glenn A.
中科院分区：
文献类型：
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作者：
Zhu, Mengqiang;Legg, Benjamin;Waychunas, Glenn A.
在酸性矿井水沃茨中和过程中早期形成的三价铁产物的物相和稳定性在很大程度上仍然未知。本文采用原位和时间分辨的快速扫描X射线吸收光谱和X射线衍射技术研究了硫酸铁溶液经NaHCO 3部分中和（[HCO 3-]/[Fe 3 +] < 3）后4 min ~ 1 h生成的产物。当[HCO 3-]/[Fe 3 +] = 0.5和0.6（初始pH分别类似于2.1和2.2）时，形成的唯一大的物种是硫酸盐络合的铁矾样分子簇，其在整个实验期间是稳定的。当[HCO 3-]/[Fe 3 +] = 1（初始pH值约为2.5）时，形成类铁锰矿分子团簇，但大多数分子团簇随后转化为施威特曼石。相比之下，当[HCO 3-]/[Fe 3 +] = 2（初始pH类似于2.7）时，中和后立即形成施氏石和较大的水铁矿颗粒。然而，水铁矿颗粒随后转化为施氏铁矿。在这两种条件下形成的施威特曼石颗粒随着时间的增加而广泛聚集。这项工作提供了新的见解的形成，稳定性和反应性的一些早期产品，可能会形成在中和天然酸性矿山废水。
The phases and stability of ferric iron products formed early during neutralization of acid mine drainage waters remain largely unknown. In this work, we used in situ and time-resolved quick-scanning X-ray absorption spectroscopy and X-ray diffraction to study products formed between 4 min and 1 h after ferric iron sulfate solutions were partially neutralized by addition of NaHCO3 ([HCO3-]/[Fe3+] < 3). When [HCO3-]/[Fe3+] = 0.5 and 0.6 (initial pH similar to 2.1 and 2.2, respectively), the only large species formed were sulfate-complexed ferrihydrite-like molecular clusters that were stable throughout the duration of the experiment. When [HCO3-]/[Fe3+] = 1 (initial pH similar to 2.5), ferrihydrite-like molecular clusters formed initially, but most later converted to schwertmannite. In contrast, when [HCO3-]/[Fe3+] = 2 (initial pH similar to 2.7), schwertmannite and larger ferrihydrite particles formed immediately upon neutralization. However, the ferrihydrite particles subsequently converted to schwertmannite. The schwertmannite particles formed under both conditions aggregated extensively with increasing time. This work provides new insight into the formation, stability and reactivity of some early products that may form during the neutralization of natural acid mine drainage.