In situ spectroscopic and solution analyses of the reductive dissolution of MnO2 by Fe(II).
In situ spectroscopic and solution analyses of the reductive dissolution of MnO2 by Fe(II).
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DOI：
10.1021/es001356d
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发表时间：
2001-02
影响因子：
11.4
通讯作者：
J. E. Villinski;Peggy A. O'Day;T. Corley;M. Conklin
中科院分区：
文献类型：
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作者：
J. E. Villinski;Peggy A. O'Day;T. Corley;M. Conklin
利用流式反应池和同步x射线吸收光谱研究了模拟酸性矿井水（pH为3,100 mM SO4(2-)）条件下Fe（II）对MnO2的还原溶解。该配置允许收集现场，实时x射线吸收近边缘结构（XANES）光谱和散装溶液样品。溶液化学分析表明，随着MnO2的还原和Fe（III）的析出，反应机理发生了变化（反应速率降低），Fe（III）主要以水合铁的形式析出。同时，我们在Mn XANES的反应物和生成物光谱中观察到一个具有jacobsite （MnFe2O4）局部结构的附加相。在实验过程中，该中间相的x射线吸光度增加，表明浓度增加。这种相的存在，可能是作为表面涂层形成的，有助于解释锰（IV）氧化物溶解速率降低的原因。在受酸性矿井排水影响的自然环境中，在经历还原性溶解的矿物表面上形成复杂的中间固相也可能影响金属向溶液释放的速度。
The reductive dissolution of MnO2 by Fe(II) under conditions simulating acid mine drainage (pH 3, 100 mM SO4(2-)) was investigated by utilizing a flow-through reaction cell and synchrotron X-ray absorption spectroscopy. This configuration allows collection of in situ, real-time X-ray absorption near-edge structure (XANES) spectra and bulk solution samples. Analysis of the solution chemistry suggests that the reaction mechanism changed (decreased reaction rate) as MnO2 was reduced and Fe(III) precipitated, primarily as ferrihydrite. Simultaneously, we observed an additional phase, with the local structure of jacobsite (MnFe2O4), in the Mn XANES spectra of reactants and products. The X-ray absorbance of this intermediate phase increased during the experiment, implying an increase in concentration. The presence of this phase, which probably formed as a surface coating, helps to explain the reduced rate of dissolution of manganese(IV) oxide. In natural environments affected by acid mine drainage, the formation of complex intermediate solid phases on mineral surfaces undergoing reductive dissolution may likewise influence the rate of release of metals to solution.