Dynamics of Magnesite Formation at Low Temperature and High pCO2 in Aqueous Solution

详细信息    查看全文

• 作者：Odeta Qafoku ; David A. Dixon ; Kevin M. Rosso ; Herbert T. Schaef ; Mark E. Bowden ; Bruce W. Arey ; Andrew R. Felmy
• 刊名：Environmental Science & Technology
• 出版年：2015
• 出版时间：September 1, 2015
• 年：2015
• 卷：49
• 期：17
• 页码：10736-10744
• 全文大小：532K
• ISSN：1520-5851

文摘

Magnesite precipitation from aqueous solution, despite conditions of supersaturation, is kinetically hindered at low temperatures for reasons that remain poorly understood. The present study examines the products of Mg(OH)₂ reaction in solutions saturated with supercritical CO₂ at high pressures (90 and 110 atm) and low temperatures (35 and 50 掳C). Solids characterization combined with in situ solution analysis reveal that the first reaction products are the hydrated carbonates hydromagnesite and nesquehonite, appearing simultaneously with brucite dissolution. Magnesite is not observed until it comprises a minor product at 7 days reaction at 50 掳C. Complete transition to magnesite as the sole product at 35 掳C (135 days) and at a faster rate at 50 掳C (56 days) occurs as the hydrated carbonates slowly dissolve under the slightly acidic conditions generated at high pCO₂. Such a reaction progression at high pCO₂ suggests that over long term the hydrated Mg-carbonates functioned as intermediates in magnesite formation. These findings highlight the importance of developing a better understanding of the processes expected to occur during CO₂ storage. They also support the importance of integrating magnesite as an equilibrium phase in reactive transport calculations of the effects of CO₂ sequestration on geological formations at long time scale.