A laboratory study of the heterogeneous reaction of nitric acid on calcium carbonate particles
A laboratory study of the heterogeneous reaction of nitric acid on calcium carbonate particles
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DOI：
10.1029/2000jd900396
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发表时间：
2000-12-16
影响因子：
4.4
通讯作者：
Grassian, VH
中科院分区：
文献类型：
--
作者：
Goodman, AL;Underwood, GM;Grassian, VH
据推测，硝酸与碳酸钙的反应，即CaCO3(s)+ 2HNO(3)(g) -> Ca(NO3)(2)(s) + CO2(g)+ H2O(g)，在大气中起着重要作用。在本研究中，使用透射 FTIR 光谱、漫反射紫外-可见光谱、透射电子显微镜和与四极杆质谱仪耦合的努森池反应器来研究 295 K 下 HNO3 对 CaCO3 的异相反应性随相对湿度的变化。使用透射 FTIR 光谱来探测气相和吸附产物，结果表明，在没有吸附水的情况下，HNO3 和 CaCO3 的反应仅限于 CaCO3 颗粒的表面。然而，在水蒸气存在下，反应大大增强，并且不限于颗粒表面，同时产生固体硝酸钙和气态二氧化碳。颗粒反应活性的增强归因于颗粒表面存在一层吸附水。颗粒表面吸附水的量很大程度上取决于反应的程度。这可以从硝酸钙与碳酸钙相比增加的亲水性来理解。使用质量校准的努森池反应器的实验数据显示，根据气相物质确定的反应化学计量偏离平衡方程的预期。颗粒表面的水吸附和溶解到水层中的气体似乎是造成这种差异的原因。在干燥条件下，测量到的样品 SET 面积的 HNO3 在 CaCO3 上的吸收系数为 2.5 + 0.1 x 10(-4)，并且发现在水蒸气存在时会增加。讨论了此处提出的结果对大气的影响。
It has been postulated that the reaction of nitric acid with calcium carbonate, namely, CaCO3(s)+ 2HNO(3)(g) -> Ca(NO3)(2)(s) + CO2(g)+ H2O(g), plays an important role in the atmosphere. In this study, transmission FTIR spectroscopy, diffuse reflectance UV-visible spectroscopy, transmission electron microscopy and a Knudsen cell reactor coupled to a quadrupole mass spectrometer have been used to investigate the heterogeneous reactivity of HNO3 on CaCO3 at 295 K as a function of relative humidity. Transmission FTIR spectroscopy was used to probe both gas-phase and adsorbed products and showed that the reaction of HNO3 and CaCO3 is limited to the surface of the CaCO3 particle in the absence of adsorbed water. However, in the presence of water vapor, the reaction is greatly enhanced and is not limited to the surface of the particle producing both solid calcium nitrate and gaseous carbon dioxide. The enhanced reactivity of the particles is attributed to the presence of a layer of adsorbed water on the particle surface. The amount of adsorbed water on the particle surface is strongly dependent on the extent of the reaction. This can be understood in terms of the increased hydrophilicity of calcium nitrate as compared to calcium carbonate, Data from experiments using a mass-calibrated Knudsen cell reactor showed the stoichiometry for the reaction determined from gas-phase species deviated from that expected from the balanced equation. Water adsorption on the particle surface and gases dissolved into the water layer appear to be the cause of this discrepancy. The measured uptake coefficient accounting for the SET area of the sample is determined to be 2.5 + 0.1 x 10(-4) for HNO3 on CaCO3 under dry conditions and is found to increase in the presence of water vapor. Atmospheric implications of the results presented here are discussed.