The presence of palygorskite and sepiolite in soils and sediments is widely used as a paleoenvironmental indicator because of their restricted environments of formation. In addition, their physical properties (especially their sorption capacity and catalytic behavior) has lead to their extensive industrial and environmental use as sorbants. The physiochemical transformation of palygorskite-sepiolite to smectite has been identified in samples from the Meigs-Attapulgas-Quincy district, an important source of these clays. Because this transformation can considerably affect the use of the palygorskite-sepiolite as industrial sorbants, the proposed project investigates the palygorskite-sepiolite to smectite transformation and its influence on the type and distribution of reactive surface sites and changes in micro-fabrics. The micro-fabric, morphology, and surface micro-topography of a natural palygorskite-sepiolite-smectite assemblage from the Meigs-Attapulgas-Quincy district will be studied using transmission electron microscopy (TEM) and atomic force microscopy (AFM), and the bulk structure of palygorskite-sepiolite will be studied using synchrotron X-ray diffraction and TEM data. Atomic models of the bulk and surface structures of palygorskite, sepiolite, and especially transitional forms will be developed from the TEM, X-ray, and AFM data. The purpose of this study is to obtain a step-by-step understanding of the transformation and to model the variation in sorption behavior. The results are important for environmental (e.g., heavy-metal adsorption) and commercial applications (e.g., bleaching and clarifying agents of oils) as well as the potential ability to use altered lithofacies to indicate paleoenvironmental information.
