The Kinetics of Silica Dissolution: An Integrated Experimental Investigation of Quartz and Amorphous Silica Reactivity in the Mixed Solute Compositions of Natural Waters

二氧化硅溶解动力学：天然水中混合溶质组合物中石英和无定形二氧化硅反应性的综合实验研究

• 批准号: 9903349
• 负责人: Patricia Dove
• 金额: $ 27.29万
• 依托单位: Georgia Tech Research Corporation
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 1999
• 资助国家: 美国
• 起止时间: 1999-12-01 至 2003-11-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=9903349&HistoricalAwards=false
• 关键词: Kinetics; Silica; Dissolution; Integrated; Experimental

9903349DoveThe dissolution kinetics of the two most abundant SiO2 polymorphs, quartz and amorphous silica, have important controls on silica partitioning within major reservoirs of Earth environments. Fluids throughout these systems typically contain significant concentrations of the major solutes, sodium, potassium, calcium and magnesium. These cations greatly enhance SiO2 dissolution rates over those measured in pure (deionized) water. In contrast, micromolar levels of aluminum exhibit an opposing rate-inhibition of silica dissolution at near-neutral to weakly-acidic pH. A quantitative and mechanistic understanding of rate-mediating effects is essential to the accuracy of numerical models which predict silica mobility. This study will answer a first order question: How do dissolved constituents act in concert as a solute mixture to control net rates of silica dissolution in the complex fluids of natural environments? Using an experimental approach that integrates techniques from geochemical kinetics and surface science, this study will quantify rates of quartz and amorphous silica dissolution (30-300 degrees C) in carefully designed solutions that contain solutes as single salts and mixtures as a function of concentration and pH. Rates will be determined using our hydrothermal mixed flow reactor system over a range of reaction affinity by adjusting steady state silica concentrations. Parallel investigations of selected silica surfaces will be conducted using in situ Atomic Force Microscopy, surface titrations, and ex situ XPS and Auger analyses. The findings will allow us to construct a quantitative model for how solutes control the reactivity of crystalline and amorphous silica in solutions that begin to approximate real-world fluids.

9903349DOVETHE的溶解动力学是两种最丰富的SIO2多晶型物，即石英和无定形二氧化硅，具有对地球环境主要储层内二氧化硅分配的重要控制。 这些系统中的流体通常包含主要溶质，钠，钾，钙和镁的浓度。 这些阳离子大大提高了SIO2溶解速率，而纯净（去离子）水中的溶解速率。 相反，微摩尔水平的铝水平表现出在近中性至弱酸性pH值下二氧化硅溶解的相反速率。 对速率定量效应的定量和机械理解对于预测二氧化硅迁移率的数值模型的准确性至关重要。 这项研究将回答一个第一阶问题：溶解成分如何共同作为溶质混合物来控制自然环境复杂流体中二氧化硅溶解的净速率？使用实验方法将地球化学动力学和表面科学的技术整合，本研究将在精心设计的溶液中量化石英和无形二氧化硅溶解（30-300摄氏度）的速率，这些溶液包含溶质作为单盐和混合物作为浓度和pH的函数。 速率将通过调节稳态二氧化硅浓度在一系列反应亲和力上使用我们的水热混合流动反应器系统确定。 将使用原位原子力显微镜，表面滴定以及Ex XPS和螺旋钻的分析对选定的二氧化硅表面进行平行研究。 这些发现将使我们能够构建一个定量模型，用于溶质如何在开始近似现实世界流体的溶液中控制晶体和无定形二氧化硅的反应性。