Vapor-Phase Sorption Kinetics for Methanol, Propan-2-OL, and 2-Methylpropan-2-OL on Al3+-, Cr3+-, and Fe3+-Exchanged Montmorillonite

C. Breen1, A. T. Deane, J. J. Flynn and D. Reynolds
School of Chemical Sciences, National Institute for Higher Education Glasnevin, Dublin 9, Ireland
School of Mathematical Sciences, National Institute for Higher Education Glasnevin, Dublin 9, Ireland
1 Current address: Chemistry Department, Sheffield City Polytechnic, Pond Street, Sheffield S1 1WB, United Kingdom.

Abstract: The rate of sorption of methanol (MeOH), propan-2-ol (i-PrOH), and 2-methyl-propan-2-ol (t-BuOH) onto a Wyoming montmorillonite saturated with Al3+-, Cr3+-, or Fe3+-cations has been studied by isothermal gravimetry in the temperature range 18°–105°C using samples of differing weights and grain-size distributions. The rate of sorption for all the alcohols increased with decreasing sample and grain size, demonstrating that inter-, rather than intraparticle mass transfer was the rate-limiting process. Optimization of the sample parameters (2 mg sample of < 45-µm grain size, pretreated at 120°C yielded integral diffusion coefficients at 18°C of 1.1 × 10−4 m2/s for t-BuOH for the Cr3+-form and 2.0 × 10−14 m2/s for MeOH and i-PrOH for the Al3+-form. In general, the rate of alcohol sorption decreased as MeOH ≥ i-PrOH > t-BuOH, but no temperature dependence of the sorption rate was observed. The alcohol sorption rate was dependent on the cation present, with Fe3+ < Cr3+ < Al3+.

Key Words: Adsorption • Alcohol • Diffusion • Grain size • Mass transfer • Montmorillonite

Clays and Clay Minerals; October 1987 v. 35; no. 5; p. 336-342; DOI: 10.1346/CCMN.1987.0350502
© 1987, The Clay Minerals Society
Clay Minerals Society (www.clays.org)