Interaction between sulphide and H2O in silicate melts
Interaction between sulphide and H2O in silicate melts
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DOI：
10.1016/j.gca.2011.03.030
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发表时间：
2011-06
影响因子：
5
通讯作者：
J. Stelling;H. Behrens;M. Wilke;J. Göttlicher;Emilie Chalmin-Aljanabi
中科院分区：
文献类型：
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作者：
J. Stelling;H. Behrens;M. Wilke;J. Göttlicher;Emilie Chalmin-Aljanabi
在温度为1000 ~ 1200℃，压力为100 ~ 200mpa的内加热气体压力容器中，实验研究了溶解水与硫化物在钠石灰硅酸钠（NCS）和三硅酸钠（NS3）熔体中的反应。在水不饱和条件下进行扩散偶联实验，偶联的一半掺杂硫化物（以FeS或Na2S的形式添加；1500-2000 ppm S的重量），另一半掺杂H2O （~ 3.0 wt.%）。此外，使用干燥的NCS玻璃圆柱体和游离的H2O流体进行了两个实验。在这里，至少在熔体/流体界面处，熔体是水饱和的。电子探针（硫）和红外显微镜（水）分析表明，水在熔体中的扩散比硫的扩散快1.5-2.3个数量级，因此，在这些实验中，水可以被认为是快速扩散的氧化剂，而硫是准不动的。在拉曼光谱中，在硫化物- H2O过渡区出现了2576 cm−1的波段，这归因于基本的S-H拉伸振动。在含硫化物熔体中扩散水前缘，在5025 cm−1处形成了新的红外吸收带（牺牲了分子H2O在5225 cm−1处的结合带）和3400 cm−1处形成了新的红外吸收带。这两个红外波段的出现和强度与ks边缘XANES光谱的系统变化相关。2466.5 eV的预边缘激发随着H2O浓度的增加而增强，而2474.0 eV的硫化物峰值相对于2477.0 eV的峰值强度减弱，2472.3 eV的特征变得更加明显（所有能量都相对于校准到2482.5 eV的硫酸盐激发）。拉曼光谱、红外光谱和XANES光谱的观察表明，在玻璃化转变过程中，玻璃中可能形成了配位良好的S2−- H2O配合物。在任何扩散偶实验中都没有观察到硫化物的氧化。与此相反，在自由H2O流体中进行的XANES实验表明，在熔体表面附近硫化物完全转变为硫酸盐，在熔体中心硫化物和硫化物共存。这可以解释为扩散偶实验中H2O活性较低，或者需要一个氢汇（例如，一种可以溶解高浓度氢气的流体），以通过S2−+ 4H2O = SO42−+ 4H2的反应促进H2O对硫化物的氧化。在任何XANES光谱中都没有检测到亚硫酸盐，这意味着如果该物质存在于熔体中，它只是一个次要或短暂的物质。
Reaction between dissolved water and sulphide was experimentally investigated in soda-lime-silicate (NCS) and sodium trisilicate (NS3) melts at temperatures from 1000 to 1200 °C and pressures of 100 or 200 MPa in internally heated gas pressure vessels. Diffusion couple experiments were conducted at water-undersaturated conditions with one half of the couple being doped with sulphide (added as FeS or Na2S; 1500–2000 ppm S by weight) and the other with H2O (∼3.0 wt.%). Additionally, two experiments were performed using a dry NCS glass cylinder and a free H2O fluid. Here, the melt was water-saturated at least at the melt/fluid interface. Profiling by electron microprobe (sulphur) and infrared microscopy (H2O) demonstrate that H2O diffusion in the melts is faster by 1.5–2.3 orders of magnitude than sulphur diffusion and, hence, H2O can be considered as a rapidly diffusing oxidant while sulphur is quasi immobile in these experiments.In Raman spectra a band at 2576 cm−1appears in the sulphide – H2O transition zone which is attributed to fundamental S–H stretching vibrations. Formation of new IR absorption bands at 5025 cm−1(on expense of the combination band of molecular H2O at 5225 cm−1) and at 3400 cm−1was observed at the front of the in-diffusing water in the sulphide bearing melt. The appearance and intensity of these two IR bands is correlated with systematic changes in S K-edge XANES spectra. A pre-edge excitation at 2466.5 eV grows with increasing H2O concentration while the sulphide peak at 2474.0 eV decreases in intensity relative to the peak at 2477.0 eV and the feature at 2472.3 eV becomes more pronounced (all energies are relative to the sulphate excitation, calibrated to 2482.5 eV). The observations by Raman, IR and XANES spectroscopy indicate a well coordinated S2−– H2O complex which was probably formed in the glasses during cooling at the glass transition. No oxidation of sulphide was observed in any of the diffusion couple experiments. On the contrary, XANES spectra from experiments conducted with a free H2O fluid show complete transformation of sulphide to sulphate near the melt surface and coexistence of sulphate and sulphide in the center of the melt. This can be explained by a lower H2O activity in the diffusion couple experiments or by the need of a sink for hydrogen (e.g., a fluid which can dissolve high concentration of hydrogen) to promote oxidation of sulphide by H2O via the reaction S2−+ 4H2O = SO42−+ 4H2. Sulphite could not be detected in any of the XANES spectra implying that this species, if it exists in the melt, it is a subordinate or transient species only.