Abstract
Vermiculite from Santa Olalla, Spain, was intercalated with tetramethylphosphonium [P(CH3)4+ = TMP], using a TMP-bromide solution at 70°C for three weeks. The resulting TMP-exchanged vermiculite, which contained a small (<5% of a site) amount of residual interlayer Ca, showed near perfect three-dimensional stacking. Cell parameters are a = 5.3492(8) Å, b = 9.266(2) Å, c = 14.505(6) Å, β = 97.08(2)°, space group is C2/m, and polytype is lM. Single-crystal X-ray refinement (R = 0.052, wR = 0.061) located two crystallographically unique sites for the phosphorus atoms (TMP molecule). The phosphorus atoms are occupied partially [P1 = 0.146(6), P2 = 0.098(5)] and are offset from the central plane of the interlayer by 1.23 Å to form two P-rich planes in the interlayer. Electrostatic interactions between the P cations and basal oxygen atoms essentially balance the negative charge associated with Al for Si substitutions in the tetrahedral sites. In addition, the orientations of the TMP molecules are probably different owing to packing constraints. The H2O site is located in the center of the interlayer, at the center of the silicate ring, and ∼3.09 Å from the Ca, which is also located on the central plane of the interlayer. Other H2O molecules are present in the interlayer, but could not be located by the diffraction experiment because they are randomly positioned in the interlayer. The tetrahedral rotation angle, α, is affected by the intercalation of TMP relative to tetramethylammonium (TMA), thus indicating that 2: 1 layers are not simply rigid substrates, and that dynamic interactions occur during reactions involving adsorption and exchange.
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References
Barrer, R.M. (1984) Sorption and molecular sieve properties of clays and their importance as catalysts. Philosophical Transactions of the Royal Society (London), A 311, 333–352.
Barrer, R.M. (1989) Shape-selective sorbents based on clay minerals: A review. Clays and Clay Minerals, 37, 385–395.
Barrer, R.M. and McLeod, D.M. (1955) Activation of mont-morillonite by ion exchange and sorption complexes of tetra-alkyl ammonium montmorillonites. Transactions of the Faraday Society, 50, 1290–1300.
Barrer, R.M. and Millington, A.D. (1967) Sorption and intra-crystalline porosity in organo-clays. Journal of Colloid Interface Science, 25, 359–372.
Barrer, R.M. and Perry, G.S. (1961) Sorption of mixtures, and selectivity in alkylammonium montmorillonites. Journal of the Chemical Society, 842–858.
Barrer, R.M. and Reay, J.S.S. (1957) Sorption and intercalation by methylammonium montmorillonites. Transactions of the Faraday Society, 53, 1253–1261.
Brown, I.D. (1977) Predicting bond length in inorganic crystals. Acta Crystallographica, B33, 1305–1310.
Cromer, D.T. and Mann, J.B. (1968) X-ray scattering factors computed from numerical Hartree-Fock wave functions. Acta Crystallographica, A24, 321–324.
de la Calle, C., Pezerat, H., and Gasperin, M. (1977) Problemes d’ordre—Desordre dans les vermiculites. Structure du minerai calcique hydrate a deux couches. Journal de Physique, Colloque, C.7 Suplement au nx 12, 38, 128–138.
Diamond, S. and Kinter, E.B. (1961) Characterization of montmorillonite saturated with short chain amine cations. Clays and Clay Minerals, 10, 163–173.
Gast, R.G. and Mortland, M.M. (1971) Self-Diffusion of alkylammonium ions in montmorillonite. Journal of Colloid Interface Science, 37, 80–92.
Kukkadapu, R.K. and Boyd, S.A. (1995) Tetramethylphos-phonium- and tetramethylammonium-smectites as adsorbents of aromatic and chlorinated hydrocarbons: Effect of water on adsorption efficiency. Clays and Clay Minerals, 43, 318–323.
Ladd, M.F.C. and Palmer, R.A. (1977) Structure Determination by X-ray Crystallography. Plenum, New York, 393 pp.
Lee, J., Mortland, M.M., and Boyd, S.A. (1989) Shape-selective adsorption of aromatic molecules from water by tetramethylammonium-smectite. Journal of the Chemical Society, Faraday Transactions I, 85, 2953–2962.
Lee, J., Mortland, M.M., Chiou, C.T., Kile, D.E., and Boyd, S.A. (1990) Adsorption of benzene, toluene, and xylene by two tetramethylammonium-smectites having different charge densities. Clays and Clay Minerals, 38, 113–120.
Luque, F.J., Rodas, M., and Doval, M. (1985) Mineralogia y genesis de los yacimientos de vermiculite de Ojen. Boletin de la Sociedad Espanola de Mineralogico, 8, 229–238.
Norrish, K. (1973) Factors in the weathering of mica to vermiculite. In Proceedings of the International Clay Conference, Madrid, 1972, J.M. Serratosa, ed., Division de Ciencias, CSIC., Madrid, 417–432.
Rowland, R.A. and Weiss, E.J. (1961) Bentonite-methylamine complexes. Clays and Clay Minerals, 10, 460–468.
Sales, K.D. (1987) Atomic scattering factors for mixed atom sites. Acta Crystallographica, A43, 42–44.
Siemens (1990) SHELXTL PLUS 4.0, Siemens Analytical X-ray Instruments, Inc., Madison, Wisconsin.
Slade, P.G., Raupach, M., and Radoslovich, E.W. (1985) Interlayer structures of the two layer hydrates of Na-and Ca-vermiculites. Clays and Clay Minerals, 33, 51–61.
Theng, B.K.G., Greenland, D.J., and Quirk, L.P. (1967) Adsorption of alkylammonium cations by montmorillonite. Clay Minerals, 7, 1–17.
Vahedi-Faridi, A. and Guggenheim, S. (1997) Crystal structure of TMA-exchanged vermiculite. Clays and Clay Minerals, 45, 859–866.
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Vahedi-Faridi, A., Guggenheim, S. Structural Study of Tetramethylphosphonium-Exchanged Vermiculite. Clays Clay Miner. 47, 219–225 (1999). https://doi.org/10.1346/CCMN.1999.0470212
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DOI: https://doi.org/10.1346/CCMN.1999.0470212