Sorption and diffusion of phenols onto well-defined ordered nanoporous monolithic silicas

S. A. El-Safty

Research output: Contribution to journalArticle

30 Citations (Scopus)

Abstract

The sorption of phenol, and o-, m-, and p-aminophenol (o-, m-, and p-AP) onto highly ordered mesoporous silicas (HOM) with cubic Im3m (HOM-1), hexagonal HI (HOM-2), 3-D hexagonal p63/mmc (HOM-3), cubic Ia3d (HOM-5), lamellar L (HOM-6), and solid phase S (HOM-8) materials has been investigated kinetically. Nanostructured silica molecular sieves have been prepared at 25 and 60°C with lyotropic liquid-crystalline phases of the nonionic surfactant (Brij 76) that was used as a structure-directing agent. Such nanostructured silicas have been studied by 29Si nuclear magnetic resonance (29Si NMR), powder X-ray diffraction (XRD), the Brunauer-Emmett-Teller (BET) method for nitrogen adsorption and surface area measurements, and transmission electron microscopy (TEM) techniques after synthesis and sorption. It was found that all materials exhibit well-defined long-range porous architectures without significant loss of the ordered texture during phenol sorption. The kinetics of phenol sorption has been studied spectrophotometrically at different temperatures (25-40°C; ±0.1 range). The sorption rate is zero order in all phenols sorbed, and increases directly in the pattern P>m-AP>o-AP>p-AP, which reflects the mobility of the phenol compounds on the particle pores. The isothermal sorption and the kinetic parameters were discussed and it was established that a diffusion-controlled process characterizes phenol sorption. Furthermore, the mechanism of phenol sorption was deduced to be predominantly particle diffusion. The diffusion coefficients were determined using Fick's equation. The trend of diffusion of all phenols onto nanoporous silica was HOM-8>HOM-2>HOM-6>HOM-5>HOM-1>HOM-3, reflecting the effect of the uniform pore size distribution and the internal surface area of the nanostructured silicas on the diffusion process.

Original languageEnglish
Pages (from-to)184-194
Number of pages11
JournalJournal of Colloid and Interface Science
Volume260
Issue number1
DOIs
Publication statusPublished - 2003 Apr 1
Externally publishedYes

Keywords

  • Diffusion
  • Kinetics
  • Nanostructured molecular sieves
  • Phenol compounds
  • Sorption
  • Surfactant

ASJC Scopus subject areas

  • Colloid and Surface Chemistry
  • Physical and Theoretical Chemistry
  • Surfaces and Interfaces

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