Direct Nanoscale Observations of CO2 Sequestration during Brucite [Mg(OH)2] Dissolution

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• 作者：J. H枚velmann ; C. V. Putnis ; E. Ruiz-Agudo ; H. Austrheim
• 刊名：Environmental Science & Technology (ES&T)
• 出版年：2012
• 出版时间：May 1, 2012
• 年：2012
• 卷：46
• 期：9
• 页码：5253-5260
• 全文大小：615K
• 年卷期：v.46,no.9(May 1, 2012)
• ISSN：1520-5851

文摘

The dissolution and carbonation of brucite on (001) cleavage surfaces was investigated in a series of in situ and ex situ atomic force microscopy (AFM) experiments at varying pH (2鈥?2), temperature (23鈥?0 掳C), aqueous NaHCO₃ concentration (10^鈥?鈥? M), and PCO₂ (0鈥? atm). Dissolution rates increased with decreasing pH and increasing NaHCO₃ concentration. Simultaneously with dissolution of brucite, the growth of a Mg鈥揷arbonate phase (probably dypingite) was directly observed. In NaHCO₃ solutions (pH 7.2鈥?.3,), precipitation of Mg鈥揷arbonates was limited. Enhanced precipitation was, however, observed in acidified NaHCO₃ solutions (pH 5, DIC 鈮?25.5 mM) and in solutions that were equilibrated under a CO₂ atmosphere (pH 4, DIC 鈮?25.2 mM). Nucleation predominantly occurred in areas of high dissolution such as deep step edges suggesting that the carbonation reaction is locally diffusion-transport controlled. More extensive particle growth was also observed after ex situ experiments lasting for several hours. This AFM study contributes to an improved understanding of the mechanism of aqueous brucite carbonation at low temperature and pressure conditions and has implications for carbonation reactions in general.