MODIFIED CLAYS FOR SORPTION AND CATALYTIC DEGRADATION OF VOCS

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The unique properties of smectite clays that are important in designing effective adsorbents and catalysts are (1) high surface area (2) high cation exchange capacity (3) swelling properties of the clay platelets and (4) high surface acidity and reactivity. Such properties make these materials inherently reactive and allows tremendous synthetic versatility to produce structures have specific properties for detoxication. Our goal is to develop a new class of materials useful for treating liquid wastes in which the contaminant is first immobilized on the clay material and then detoxified via catalysis on the clay surface. The clay-based materials being developed for this purpose are (1) transition metal saturated clays (2) organo-metal-clays (3) piliared clays and (4) delaminated clays. An additional objective is to develop and use organo- clays as components of clay barriers (e.g., bentonite slurry walls) to improve the containment characteristics of waste disposal reservoirs. Metal clays are versatile catalysts which can be used to form reactive radical cations of organic toxicants such as TCE, benzene, dioxins and phenols. These reactive radical species are subject of a variety of potential reactions to form less toxic products. Important reactions such as polymerization and dechlorination have been achieved. Organic cations can also be placed on the surface of smectite clays to impart hydrophobic properties important for adsorption of trace organic contaminants from aqueous streams. The desired sorptive and catalytic properties can be combined by using a mixture of organic and metallic cations. Pillared and delaminated clays are microporous to macroporous derivatives formed by the reaction of natural clays with robust polyoxocations. The relatively large pore sizes of these clays make them ideal adsorbents for large chlorinated hydrocarbons. Also, metal catalysts can be introduced into their structures to facilitate subsequent oxidation of the adsorbed toxicant.