Water vapour adsorption and contrast-modified SAXS in microporous polymer-based carbons of different surface chemistry

K. László, Cyrille Rochas, Erik Geissler

Research output: Contribution to journalArticle

11 Citations (Scopus)

Abstract

The adsorption of water vapour on highly microporous activated carbons with different surface chemistry is investigated by small angle X-ray scattering (SAXS) as well as by adsorption isotherms. The water changes the intensity of the SAXS in a way that depends on how the pores are filled. With wetting liquids such as hexane, a pseudo binary model can be assumed in which pore-filling in reciprocal space q is described by a density function p(q). For water, clusters develop, even in the most oxidized carbon, creating a fully ternary system. In the Porod scattering region, however, the final slope is insensitive to the liquid-vapour interfaces. In this region, for the less oxidized samples, p(q) shows reasonable agreement with the adsorption isotherms. At low relative pressure P/P 0, however, the SAXS results indicate a small degree of filling (about 10%) that is not reflected in the isotherms. The highly oxidized sample attains a degree of filling of about 70% that, unlike the corresponding isotherm, is constant for P/P 0>0. These differences may be due to kinetic effects and/or ageing, involving either redistribution of the water molecules or modifications of the surface groups.

Original languageEnglish
Pages (from-to)447-455
Number of pages9
JournalAdsorption
Volume14
Issue number4-5
DOIs
Publication statusPublished - Oct 2008

Fingerprint

Steam
Surface chemistry
X ray scattering
Water vapor
water vapor
Polymers
isotherms
Carbon
chemistry
Adsorption isotherms
Adsorption
adsorption
Isotherms
Water
carbon
polymers
scattering
x rays
Liquids
Hexanes

Keywords

  • Activated carbon
  • Interfacial properties
  • Small angle X-ray scattering
  • Surface treatment

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry
  • Process Chemistry and Technology
  • Chemical Engineering(all)

Cite this

Water vapour adsorption and contrast-modified SAXS in microporous polymer-based carbons of different surface chemistry. / László, K.; Rochas, Cyrille; Geissler, Erik.

In: Adsorption, Vol. 14, No. 4-5, 10.2008, p. 447-455.

Research output: Contribution to journalArticle

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