Colloid and Polymer Science

, Volume 269, Issue 5, pp 483–489 | Cite as

Surface characterization and heats of adsorption of chromatographic alumina gel

  • M. Afzal
  • M. Khan
  • H. Ahmad
Original Contributions

Abstract

The porous nature of chromatographic alumina gel has been investigated by adsorption/condensation processes and electron microscopy. Having 63% porosity, the gel is very porous. Total pore volume as determined by the fluid-displacement method is 0.497 cm3 g−1. Its specific surface area, as determined by water vapor adsorption, is 225 m2 g−1. Micropore volume, as determined by utilizing Gurwitsch's rule, turns out to be 0.262 cm3 g−1. The greater portion of the surface area and pore volume occurs in small and transitional pores, with average pore radii (hydraulic) less than 2.1 nm.

Organic vapors, such as methyl ethyl ketone, acetone, methyl acetate, and methyl alcohol, were adsorbed on the gel between 0 and 36°C under vacuum, and the data were recorded on a Cahn-1000 electrobalance device. Isosteric heats of adsorption were calculated by applying the Clausius Clapeyron equation to the adsorption isosters at different surface coverages. Two types of adsorption processes, one with low activation energy and other with high activation energy can be distinguished. The increase in values ofq st indicates that increasing temperature changes physical adsorption into chemisorption.

Key words

Surface characterization heats of adsorption alumina gel surface studies adsorption thermodynamics 

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Copyright information

© Steinkopff-Verlag 1991

Authors and Affiliations

  • M. Afzal
    • 1
  • M. Khan
    • 1
  • H. Ahmad
    • 1
  1. 1.Department of ChemistryQuaid-Azam UniversityIslamabadPakistan

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