Department of Earth Sciences, Nanjing University, Nanjing, Jiangsu, 210093, People's Republic of China.
Environ Sci Technol. 2010 Jan 1;44(1):406-11. doi: 10.1021/es9017656.
Carbonation of natural brucite in H2O and diluted HCl is investigated at room temperature and moderate pCO2 to explore the products' mineralogy and reaction kinetics. Results show nesquehonite is by far the dominant carbonate species formed, despite its poorer thermodynamic stability relative to magnesite and possibly hydromagnesite. Time-dependent measurements reveal carbonate formation within 30 min, regardless of the original acidity of the slurry. However, while the fraction of reacted brucite in H2O increases gradually over time and approaches unity ( approximately 98%) at 2.5 h, it rises rapidly in HCl within the first hour and levels off thereafter, leaving a significant amount of brucite unreacted. Such behavior suggests that the initial quantity of Mg2+ affects the reaction kinetics. Fitting a pseudo first-order rate law to the data yields a higher rate constant for the HCl experiments. These observations may imply that the carbonation does not proceed through heterogeneous reaction between gaseous CO2 and solid brucite. Solution chemistry analysis indicates that most CO2 stays in aqueous phase in both media; however, the concentration of HCO3(-) becomes high in H2O after about 2 h, agreeing with the observed inferior carbonation extent in HCl.
在室温下，用 H2O 和稀 HCl 对天然水镁石进行碳酸化作用研究，以探索产物的矿物学和反应动力学。结果表明，尽管菱镁矿和可能的水镁石在热力学上更稳定，但一水软锰矿迄今为止仍是形成的主要碳酸盐物种。时变测量表明，无论浆液的原始酸度如何，碳酸盐的形成都在 30 分钟内发生。然而，尽管在 H2O 中反应的水镁石分数随着时间的推移逐渐增加，并在 2.5 小时后接近 1（约 98%），但在 HCl 中在前一个小时内迅速增加，随后趋于稳定，留下大量未反应的水镁石。这种行为表明初始 Mg2+的数量会影响反应动力学。用拟一级速率定律对数据进行拟合，得到 HCl 实验的更高速率常数。这些观察结果可能意味着碳酸化作用不是通过气相 CO2 和固体水镁石之间的多相反应进行的。溶液化学分析表明，在两种介质中，大多数 CO2 仍留在水相；然而，在 H2O 中约 2 小时后 HCO3(-)的浓度变得很高，与 HCl 中观察到的较差的碳酸化程度一致。
