Pan Shu-Yuan, Lai Barry, Ren Yang
Department of Bioenvironmental Systems Engineering, National Taiwan University Taipei City 10617 Taiwan
X-ray Science Division, Advanced Photon Source, Argonne National Laboratory Argonne IL 60439 USA.
RSC Adv. 2019 Oct 2;9(53):31052-31061. doi: 10.1039/c9ra06118e. eCollection 2019 Sep 26.
In order to ensure the viability of CO mineralization and utilization using alkaline solid waste, a mechanistic understanding of reactions at mineral-water interfaces was required to control the reaction pathways and kinetics. In this study, we provided new information for understanding the reactions of CO mineralization and utilization at mineral-water interfaces. Here we have carried out high-energy synchrotron X-ray analyses to characterize the changes of mineral phases in petroleum coke fly ash during CO mineralization and their subsequent utilization as supplementary cementitious materials in cement mortars. The 2-D synchrotron patterns were converted to 1-D diffraction patterns and the results were then interpreted the Rietveld refinement. The results indicated that there was a continuous source of calcium ions mainly due to the dissolution of CaO and Ca(OH) in fly ash. This would actually enhance the driving force of saturation index at the solid-fluid interfacial layer, and then could eventually result in the nucleation and growth of calcium carbonate (calcite) at the interface. A small quantity of CaSO (anhydrite) in fly ash was also dissolved and simultaneously converted into calcite. In addition, the calcium sulfate in fly ash would effectively prevent the early hydration of tricalcium aluminate in blended cement, and thus could avoid the negative impact on its strength development. The proposed reaction mechanisms were also qualitatively verified by X-ray fluorescence mapping and electron microscopy. These results would help to design efficient reactors and cost-effective processes for CO mineralization and utilization in the future.
为确保利用碱性固体废弃物进行CO矿化和利用的可行性，需要从机理上理解矿物 - 水界面的反应，以控制反应途径和动力学。在本研究中，我们提供了新的信息来理解CO在矿物 - 水界面的矿化和利用反应。在此，我们进行了高能同步加速器X射线分析，以表征石油焦粉煤灰在CO矿化过程中矿物相的变化，以及随后将其用作水泥砂浆中的辅助胶凝材料的情况。将二维同步加速器图谱转换为一维衍射图谱，然后通过Rietveld精修对结果进行解释。结果表明，主要由于粉煤灰中CaO和Ca(OH)的溶解，存在持续的钙离子来源。这实际上会增强固 - 液界面层处饱和指数的驱动力，进而最终导致碳酸钙（方解石）在界面处成核和生长。粉煤灰中的少量CaSO₄（硬石膏）也会溶解并同时转化为方解石。此外，粉煤灰中的硫酸钙会有效防止混合水泥中铝酸三钙的早期水化，从而避免对其强度发展产生负面影响。所提出的反应机理也通过X射线荧光映射和电子显微镜进行了定性验证。这些结果将有助于未来设计高效的反应器和具有成本效益的CO矿化及利用工艺。
