Dissolution of the (001) surface of galena: An in situ assessment of surface speciation by fluid-cell micro-Raman spectroscopy
Dissolution of the (001) surface of galena: An in situ assessment of surface speciation by fluid-cell micro-Raman spectroscopy
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DOI：
10.2138/am.2007.2181
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发表时间：
2007-04
影响因子：
3.1
通讯作者：
G. Giudici;P. Ricci;P. Lattanzi;A. Anedda
中科院分区：
文献类型：
--
作者：
G. Giudici;P. Ricci;P. Lattanzi;A. Anedda
摘要用微区拉曼光谱和溶液化学研究了方铅矿（001）解理面在氧饱和溶液中溶解的化学演化。在这种新型的μRS装置中，流体池中的溶液是连续更新的。一个相当厚的（几十到几百纳米）层形成在方铅矿表面的溶液pH值在1和5.8之间。这一表面层是由铅的氧化物，硫酸盐和亚稳物种的硫。天然硫在pH 1和4.6下形成，但在pH 5.8下不是主要的表面物质。通过溶液化学测量的溶解速率随着pH和反应时间而降低。在这些实验中，在这样低的pH值的铅氧化物的形成与热力学预测的基础上在宏观尺度（本体溶液）的属性。表面形态的原位评估证实了硫可以在界面处部分氧化，并表明硫氧化过程取决于pH值。我们认为，在溶解的分子氧与S原子反应期间，硫氧化可能至少部分发生在方铅矿表面或附近。在反应的第一步之后，氧与Pb离子结合以在界面处形成Pb氧化物。
Abstract The chemical evolution of the galena (001) cleavage surface dissolving in oxygen-saturated solutions was investigated by fluid-cell micro-Raman Spectroscopy (μRS) and solution chemistry. In this novel design of μRS apparatus, the solution in the fluid cell is continuously renewed. A fairly thick (several tens to hundreds of nanometers) layer forms at the galena surface in solutions with pH between 1 and 5.8. This surface layer is composed of Pb oxides, sulfates, and metastable species of sulfur. Native sulfur forms at pH 1 and 4.6, but is not a predominant surface species at pH 5.8. Dissolution rates, measured by solution chemistry, decrease with pH and reaction time. The formation of Pb oxides in these experiments at such low pH values contrasts with thermodynamic predictions based on properties at the macroscale (bulk solution). The in situ assessment of surface speciation confirms that sulfur can partially oxidize at the interface, and indicates that this process of sulfur oxidation depends on pH. We propose that sulfur oxidation may take place, at least partially, during the reaction of dissolved molecular oxygen with S atoms at the galena surface, or in the immediate vicinity. After this first step of reaction, oxygen combines with Pb ions to form Pb oxide at the interface.