TETRAHYDROPYRAN, AND 1,4-DIOXAN BY A13+- AND Cra+-EXCHANGED MONTMORILLONITE

dioxan (DIOX) onto a Wyoming montmorillonite saturated with AP + or Cr 3+ has been studied by isothermal gravimetry in the temperature ange 18 ~ to 105 ~ using samples of different weights and grain-size distributions. The rate of sorption for all the cyclic ethers increased with decreasing sample and grain size, demonstrating that inter-, rather than intraparticle mass transfer was rate-determining. Optimization of the sample parameters (2 mg sample of <45-~tm grain size, pretreated at 120 ~ yielded integral diffusion coefficients at 18 ~ of 0.5 x 10-14 m2/s for DIOX for the Cr3+-clay to 3.5 • 10-~4 m2/s for THF for the A13+-clay; however, no temperature or cationic dependence ofthe cyclic ether uptake was observed. In general, the rate ofsorption of the cyclic ethers increased as THF>- THP> DIOX indicating that the sorption rate of THF and THP was dependent on concentration r that DIOX sorption was retarded by bidentate coordination toaluminum ions at the edges of the clay platelets. Key Words--Adsorption, Cyclic ethers, Diffusion, Montmorillonite, Vapor