Toward a Model for Mineral Dissolution Kinetics

本研究的目的是比较酸碱 系列矿物表面化学和溶解动力学 相似的组成和不断增加的结构复杂性。 这 系列包括溴闪石（钠闪石，石英），菲纳克石， 金绿宝石（和绿柱石）。 本研究旨在建立一个 简单氧化物溶解模型之间的联系， 容易研究，和岩石形成矿物含有几个 溶解的潜在场所。 这项研究需要确定溶解速率的法律， 黄绿柱石、金绿柱石和绿柱石作为pH值的函数， 温度在15-80摄氏度的范围内。 数据已存在 其他矿物质。 研究的一个重要部分是 溶解活化能与 氢离子和羟基离子吸附的图解。 这 比较将确定均衡中的变化 吸附率与pH值的关系解释了所报道的变化 溶解活化能随溶液pH的变化。 所提出的矿物具有独特的性质， 适合建立上述联系。 全部溶解 足够慢，溶质扩散不影响 反应速率 因此，酸碱表面化学， 控制反应速率的pH依赖性，可以容易地 表征了 最重要的是， 阳离子转化为氧在整个矿物系列中是一致的。 这项研究涉及对动力学的基本理解 溶解在常见的造岩矿物中， 岩石风化的基础是变质作用。

The objective of this study is to compare the acid-base surface chemistry and dissolution kinetics of a series of minerals of similar composition and increasing structural complexity. This series includes bromellite (corundum, quartz), phenakite, chrysoberyl (and beryl). This study is intended to establish a link between models for dissolution of simple oxides, which are easily studied, and rock-forming minerals containing several potential sites for dissolution. The research entails determining the dissolution rate laws for phenakite, chrysoberyl and beryl as a function of pH and temperature in the range of 15-80 degrees C. Data already exist for the other minerals. An essential part of the research is comparison of the dissolution activation energies with the enthalpies of hydrogen- and hydroxyl-ion adsorption. This comparison will determine the extent that variations in equilibrium adsorption enthalpies with pH account for the reported variation in dissolution activation energies with solution pH. The proposed minerals have properties which are uniquely suited to establish the aforementioned link. All dissolve sufficiently slowly that solute diffusion does not affect the reaction rate. Thus the acid-base surface chemistry, which controls the pH-dependence of the reaction rate, can be easily characterized. Most importantly, the coordination chemistry of cations to oxygens is consistent in the entire series of minerals. This research involves fundamental understanding of the kinetics of dissolution in common rock-forming minerals necessary to get at the basics of rock weathering are metamorphism.