Silicate Dissolution in Organic-Rich Aqueous Systems: Reaction Mechanisms and Rate Controls

富含有机物的水系统中的硅酸盐溶解：反应机制和速率控制

• 批准号: 9105778
• 负责人: Philip Bennett
• 金额: $ 12.93万
• 依托单位: University of Texas at Austin
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 1991
• 资助国家: 美国
• 起止时间: 1991-06-01 至 1994-05-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=9105778&HistoricalAwards=false
• 关键词: Silicate; Dissolution; Organic; Rich; Aqueous

The goal of the proposed research is to examine the role of organic-silica and organic-aluminum complexes in feldspar dissolution. Organic acids have been implicated as important reactants in a number of weathering environments, and are suggested to accelerate feldspar dissolution, increase feldspar solubility, mobilize aluminum and silica in solution, and alter the equilibrium between the solution and the precipitated secondary phases. The precise mechanism by which organic acids influence feldspar dissolution, however, and their significance in varying surficial weathering processes, is not well established. In natural waters at circum-neutral to acidic pH, there appears to be four primary processes: proton hydrolysis, solution complexation of aluminum, solution complexation of silica, and surface coordination resulting in accelerated dissolution. Depending on the environmental conditions and the organic acid species present, the dominant mechanism may be one or a combination of any of the four possibilities. The approach for the proposed study is to combine three independent methodologies to investigate a simple feldspar-aqueous- -electrolyte system. Dissolution experiments will be done to quantify the effects of various organic-acid anions on dissolution kinetics as a function of pH, temperature, and solution composition. These experiments are designed to separate the parallel mechanisms of acidic hydrolysis, solution complexation, and surface interactions. Spectroscopic experiments will investigate the stability and formation kinetics of the solution complexes of aluminum and silica. Raman, FTIR, UV-VIS, C and Si methods will be used to gain information on bonding environment, stoichiometry, and stability as a function of pH and temperature, using the same solution compositions as in the dissolution experiments. These studies will be combined with molecular orbital modeling relationships of the organic-acid--metal combinations as a function of organic-acid functional-group chemistry. The results of the solution complexation studies and modeling will be used to calibrate large-scale molecular-mechanics models of silicate surfaces that will be used to test the hypothetical interactions derived from the dissolution experiments. This is a two-year study which will interface with ongoing studies of field locations at which silica-organic complexation has been identified as a significant weathering mechanism, and these field sites will be used to test possible models of interaction. In addition, the study will involve collaboration with Los Alamos National Laboratory in developing methods of spectroscopic analysis of organic-metal complexes in aqueous systems.

这项研究的目的是研究 长石中的有机硅和有机铝复合物 解散 有机酸被认为是重要的 反应物在一些风化环境，并建议 加速长石溶解，增加长石溶解度， 使溶液中的铝和二氧化硅流动， 在溶液和沉淀的第二相之间。 的 有机酸影响长石的精确机理 溶解，然而，和他们的意义，在不同的表面 风化过程，并没有很好地建立。 在自然沃茨中 在环中性到酸性pH下，似乎有四种主要的 工艺：质子水解，铝的溶液络合， 二氧化硅的溶液络合和表面配位 加速溶解。 根据环境 条件和存在的有机酸物种，占主导地位的 机制可以是四个机制中的一个或任何一个的组合。 可能性 拟议研究的方法是将联合收割机 独立的方法来调查一个简单的菱锌矿-水- - 电解质系统。 将进行溶出实验， 量化各种有机酸阴离子对溶解的影响 作为pH值、温度和溶液的函数的动力学 混合物. 这些实验旨在分离 酸水解，溶液络合， 和表面相互作用。 光谱实验将 研究溶液的稳定性和形成动力学 铝和二氧化硅的复合物。 拉曼、FTIR、UV-VIS、 C和 硅方法将用于获得有关键合的信息 环境、化学计量和稳定性作为pH值的函数， 温度下，使用与本发明中相同的溶液组合物， 溶解实验 这些研究将与 有机酸-金属的分子轨道模型关系 组合作为有机酸官能团的函数 化学. 溶液络合研究的结果和 建模将用于校准大规模分子力学 硅酸盐表面的模型，将用于测试 来自溶解实验的假设相互作用。 这是一项为期两年的研究，将与正在进行的 研究现场的位置，在那里二氧化硅-有机络合， 被认为是一种重要的风化机制，这些 将利用实地地点来测试可能的互动模式。 此外，该研究还将与洛斯阿拉莫斯国家实验室合作， 国家实验室在发展光谱分析方法 有机金属配合物在水溶液中的应用