The Stability and Surface Chemistry of Allophane and Imogolite

本研究的目的是建立依赖的表面特性的合成水铝英石和伊毛戈兰的结构特征，确定水铝英石和伊毛戈兰的热力学稳定性（亚稳性），并开始调查比较合成和天然水铝英石和伊毛戈兰的表面和结构特征和稳定性。Al的配位和Si的配位环境将通过MAS-NMR和本体组成通过溶解和通过能量色散X射线分析来确定。通过电位滴定、离子保留和电泳测定表面酸度和电荷特性。一价离子的碱和卤化物系列将被用来测试模型的离子选择性和大的有机阳离子将被用来测试一个假设，提出不平等的分布的阳离子和离子之间的表面和内部网站。我们将开始比较合成材料和从土壤和浮石沉积物中分离出来的材料的表面和体积特性。所有材料的稳定性测定将基于溶解度实验。水铝英石和伊毛沸石是非结晶铝硅酸盐，存在于各种土壤中。从理论的角度来看，它们是有趣的，因为它们表现出广泛的组成，同时保持一些一致和独特的结构特征。从实用的角度来看，其非常高的比表面积对土壤性质的影响超过了其质量的预期。已知它们影响持水能力、肥力、有机化合物的降解或聚合以及铝在土壤中的运输。这项研究的潜在应用也可能扩展到解决废物处理、雨水和污染问题。

The objectives of this research are to establish the dependence of surface characteristics on structural characteristics of synthetic allophane and imogolite, determine the thermodynamic stability (metastability) of allophane and imogolite and to initiate investigations comparing the surface and structural characteristics and stability of synthetic and naturally-occurring allophane and imogolite. The coordination of Al and the coordination environment of Si will be determined by MAS-NMR and bulk composition by dissolution and by energy-dispersive X-ray analysis. Surface acidity and charge characteristics will be determined by potentiometric titration, ion retention, and electrophoresis. Monovalent ions of the alkali and halide series will be used to test models of ion selectivity and large organic cations will be used to test a hypothesis that proposed unequal distribution of cations and ions between surface and interior sites. We will initiate a comparison of surface and bulk characteristics between the synthetic materials and their counterparts isolated from soils and pumice deposits. Stability determinations on all materials will be based on solubility experiments. Allophane and imogolite are noncrystalline aluminosilicates which occur in a variety of soils. They are interesting from a theoretical standpoint because they exhibit a wide range of composition while maintaining some consistent and unique structural characteristics. From a practical standpoint, their very high specific surface areas impart an influence on soil properties in excess to what is expected from their mass. They are known to influence water holding capacity, fertility, degradation or polymerization of organic compounds, and transport of Al in soils. Potential applications of this research may also extend to addressing problems in waste disposal, and rain and pollution.