Organic cation exchange, clay

Teppen, B. J., and Aggarwal, V. (2007).Thermodynamics of organic cation exchange selectivity in smectites. Clays Clay Min. 55,119-130. 

Soil Textural Class pH %Sand % Silt %Clay % Organic Cation Exchange Capacity (meq/lOOg)... 

Cations based on substituted silsesquioxanes have also been intercalated [7]. On heating the ion-exchanged clay minerals water is evolved, but oxycation or oxide pillars keep the siliceous layers apart. These materials have enhanced thermal stability compared with clay minerals expanded with organic cations. Expanded clay minerals cover at least as wide a range of accessibilities to the interlamellar micropore spaces as the zeolites, but the pore characteristics of clay minerals with inorganic pillars need more detailed investigation. 

Organic cation exchange on to clay interlayers is, to an extent, largely determined by [15] ... 

Stefan Dultz., Jong Hyok An., Beate Riebe. Organic cation exchanged montmorillonite and vermiculite as adsorbents for Cr(VI) Effect of layer charge on adsorption properties. Applied Clay Science. 2012, 67,125-133. 

It is believed that clay minerals promote organic reactions via an acid catalysis [2a]. They are often activated by doping with transition metals to enrich the number of Lewis-acid sites by cationic exchange [4]. Alternative radical pathways have also been proposed [5] in agreement with the observation that clay-catalyzed Diels-Alder reactions are accelerated in the presence of radical sources [6], Montmorillonite K-10 doped with Fe(III) efficiently catalyzes the Diels-Alder reaction of cyclopentadiene (1) with methyl vinyl ketone at room temperature [7] (Table 4.1). In water the diastereoselectivity is higher than in organic media in the absence of clay the cycloaddition proceeds at a much slower rate. 

The main parameters that affect the cost-effectiveness of soil washing include the physicochemical parameters of the soil (grain size distribution, cation exchange capacity, percentage of silt, clay, or organic matter), and the type and concentration of contaminants. 

Clay minerals or phyllosilicates are lamellar natural and synthetic materials with high surface area, cation exchange and swelling properties, exfoliation ability, variable surface charge density and hydrophobic/hydrophilic character [85], They are good host structures for intercalation or adsorption of organic molecules and macromolecules, particularly proteins. On the basis of the natural adsorption of proteins by clay minerals and various clay complexes that occurs in soils, many authors have investigated the use of clay and clay-derived materials as matrices for the immobilization of enzymes, either for environmental chemistry purpose or in the chemical and material industries. 

Jaynes WF, Vance GF (1999) Sorption of benzene, toluene, ethylbenzene and xylene (BTEX) compounds by hectorite clays exchanged with aromatic organic cations. Clays Clay Miner 47 358-365 Johnston CT, De Oliveira MF, Teppen BJ, Sheng G, Boyd SA (2001) Spectroscopic study of nitroaromatic-smectite sorption mechanisms. Environ Sci Technol 35 4767-4772... 

Laird DA, Barriuso E, Dowdy RH, Koskinen WC (1992) Adsorption of atrazine on smectites. Soil Sci Soc Am J 56 62-67 LeBaron PC, Wang Z, Pinnavaia TJ (1999) Polymer-layered silicate nanocomposites an overview. Appl Clay Sci 15 11-29 Lee J-F, Crum JR, Boyd SA (1989) Enhanced retention of organic contaminants by soil exchanged with organic cations. Environ Sci Technol 23 1365-1372 Lee J-F, Mortland MM, Boyd SA, Chiou CT (1989a) Shape-selective adsorption of aromatic molecules from water by tetramethylammonium-smectite. J Chem Soc Faraday Trans I 8 2953-2962... 

Exchange of organic ammonium cations. Exchange selectivity of monovalent alkyl ammonium cations in montmorillonites (40-41) and octahedrally substituted synthetic clay minerals (laponite) increases with their chain length (42) and along the series... 

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