The sorption and encapsulation properties of a variety of zeolitic minerals have been investigated using the rare gases helium, neon, argon and krypton as sorbates. High pressure (up to 15,000 p.s.i.) and high temperature (up to 580°C.) techniques were used to effect sorption of the gases. The high pressure sorption apparatus was described in detail. Minerals investigated included the crystalline silica polymorphs, sodalites, cancrinites, stilbite, heulandite and the synthetic zeolite Rb-M. Preliminary results were reported for mesolite, scolecite, thomsonite, attapulgite, sepiolite, beryl and cordierite. Sorption isotherms and desorption kinetic isotherms were determined in most cases, enabling calculations to be made of heats of solution and activation energies for diffusion. Where macro-crystalline samples were used (silica polymorphs, stilbite and heulandite) sample surface areas were estimated using a projected area method, and diffusion coefficients thus evaluated. The desorption kinetic isotherms were characteristically sigmoid in shape, having a non-isothermal initiation period. Diffusion in such a system had not been considered previously, and an applicable solution to the diffusion equations was developed and described in detail. Heats of solution were determined for the following systems: helium in a-, β1- and β2- tridymites, and a- and β- cristobalites; neon in β2-tridymite, β-cristobalitei, basic-cancrinite and heulandite; argon in stilbite and basic sodalite; krypton in Rb-M, basic sodalite and extracted basic sodalite. Activation energies for diffusion were also calculated for the above pairs, and in addition for argon in Rb-M, stilbites and heulandites; and krypton in stilbites. Diffusion coefficients were evaluated for helium in a-tridymite and a-cristobalite; neon in a-, β1- and β2-tridymites, heulandite and stilbite; argon in various stilbites and heulandites; and krypton in stilbites. Using the Lennard-Jones 12-6 potential detailed theoretical calculations were made of the interaction energies between the rare gases and the oxygen frameworks and cations in the structures of sodalite, β2- tridymite, a-cristobalite and β-cristobalite. In all cases agreement was good between calculated and experimental parameters using the London and Slater- Kirkwood dispersion constants.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:622978 |
| Date | January 1967 |
| Creators | Vaughan, David Evan William |
| Publisher | Imperial College London |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://hdl.handle.net/10044/1/17604 |
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