Laboratoire des Interactions Microorganismes-Minéraux-Matière Organique dans les Sols, UMR 7137 CNRS, BP 70239, Vandoeuvre-lès-Nancy Cedex 54506, France.
J Colloid Interface Sci. 2010 Mar 15;343(2):433-8. doi: 10.1016/j.jcis.2009.11.058. Epub 2009 Dec 1.
Anisotropic textural and crystallographic properties of phyllosilicate particles often influence the mineral weathering rate. The purpose of this study was to investigate how the changes in mineral surfaces (basal vs. edge) as a result of changes in crystal size control the dissolution of the mineral. Different nano-size fractions of Na-exchanged nontronites (NAu2 and NAu1) were immobilized in a silica gel and then incubated under acidic conditions using HNO(3) at 28 degrees C for 5 days. For each sample, the dissolution behavior was analyzed by measuring the amount of iron released from the mineral lattice. The results showed that for a given pH, a decrease in particle size significantly increased NAu2 and NAu1 dissolution. At pH 1.5, 7.2% of the total iron of the highest size sample of NAu2 was released in solution whereas this proportion increased up to 25% for the smallest size fraction. The percentage of total iron extracted from NAu1 at the same pH (1.5) was less important: 3.5% and 6.5% for higher and smaller size fractions, respectively. The observed increase in dissolution was not directly correlated to the increase in the amount of edge faces, suggesting that all mineral surfaces contributed to mineral dissolution. In the present case this may be related to the fact that 8% and 2% of total iron of NAu2 and NAu1, respectively, are located in the tetrahedral sheet. In conclusion, the basal surface of nontronites plays an important role in the weathering process.
页硅酸盐颗粒各向异性的纹理和结晶特性通常会影响矿物的风化速率。本研究旨在探讨矿物表面（基面与边缘）因晶体尺寸变化而发生的变化如何控制矿物的溶解。采用不同纳米级分数的 Na 交换蒙脱石（NAu2 和 NAu1）固定在硅胶中，然后在 28°C 下用 HNO3 在酸性条件下孵育 5 天。对于每个样品，通过测量从矿物晶格中释放的铁量来分析溶解行为。结果表明，在给定 pH 值下，粒径减小显著增加了 NAu2 和 NAu1 的溶解。在 pH 1.5 时，NAu2 最大粒径样品的总铁中有 7.2%释放到溶液中，而最小粒径分数的这一比例增加到 25%。在相同 pH（1.5）下，从 NAu1 中提取的总铁的百分比要小一些：高粒径和小粒径分数分别为 3.5%和 6.5%。观察到的溶解增加与边缘面数量的增加没有直接相关性，这表明所有矿物表面都有助于矿物溶解。在这种情况下，这可能与 NAu2 和 NAu1 分别有 8%和 2%的总铁位于四面体片有关。总之，非脱石的基面在风化过程中起着重要作用。
