Formation of submicron magnesite during reaction of natural forsterite in H₂O-saturated supercritical CO₂

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• 作者：Odeta Qafoku ; ^{Odeta.qafoku@pnnl.gov" class="auth_mail} ; Jianzhi Hu ; Nancy J. Hess ; Mary Y. Hu ; Eugene S. Ilton ; Ju Feng ; Bruce W. Arey ; Andrew R. Felmy
• 刊名：Geochimica et Cosmochimica Acta
• 出版年：1 June 2014
• 年：2014
• 卷：134
• 期：Complete
• 页码：197-209
• 全文大小：2573 K

文摘

Natural forsterite was reacted in bulk liquid water saturated with supercritical CO₂ (scCO₂) and scCO₂ saturated with water at 35–80 °C and 90 atm. The solid reaction products were analyzed with nuclear magnetic resonance (NMR), scanning electron microscopy (SEM), and confocal Raman spectroscopy. Two carbonate phases, nesquehonite (MgCO₃·3H₂O) and magnesite (MgCO₃), were identified with the proportions of the two phases depending on experimental conditions. In liquid water saturated with scCO₂, nesquehonite was the dominant carbonate phase at 35–80 °C with only a limited number of large, micron size magnesite particles forming at the highest temperature, 80 °C. In contrast, in scCO₂ saturated with H₂O magnesite formation was identified at all three temperatures: 35, 50, and 80 °C. Magnesite was the dominant carbonation reaction product at 50 and 80 °C, but nesquehonite was dominant at 35 °C. The magnesite particles formed under scCO₂ saturated with H₂O conditions exhibited an extremely uniform submicron grain-size and nearly identical rhombohedral morphologies at all temperatures. The distribution and form of the particles were not consistent with nucleation and growth on the forsterite surface.