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Chromatography of liquid‐phase adsorption on octadecylsilyl‐silica gel

1992; Wiley; Volume: 38; Issue: 6 Linguagem: Inglês

10.1002/aic.690380611

1547-5905

Kanji Miyabe, Motoyuki Suzuki,

Surfactants and Colloidal Systems

Abstract Intraparticle diffusion and adsorption equilibrium on octadecylsilyl‐silica gel (ODS) were studied. As an adsorbate, p‐tert‐octylphenol (PTOP) was employed. The intraparticle diffusion coefficient was measured by the chromatographic technique and the moment analysis at zero and several surface coverages. Adsorption isotherms can be correlated by the Langmuir equation. The isosteric heat of adsorption and the activation energy of surface diffusion were constant regardless of the amount adsorbed. These results suggest that ODS has an energetically homogeneous surface. The effect of solvent on isosteric heat of adsorption in the liquid system was discussed qualitatively by the solvophobic theory. Surface diffusion coefficient of PTOP on ODS was of the order of 10 −7 to 10 −6 cm 2 /s. Surface diffusion was dominant for the intraparticle diffusion in ODS, and its coefficient increased with an increase in the amount adsorbed. Positive concentration dependence of the surface diffusion coefficient was interpreted in terms of diffusion by potential chemical driving force.