Critical discussion of the use of adsorption measurements from the liquid phase for surface area estimation

G. Schay, L. Nagy

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63 Citations (Scopus)

Abstract

Any adsorption method for estimating surface areas of adsorbents is based on the determination of monolayer capacity. The present paper is concerned with the utilization of adsorption isotherms of mixtures of two completely miscible nonelectrolyte liquids for this purpose. Sufficient reliability and reproducibility of experimental isotherms being difficult to obtain, the main factors decisive in this respect and the normally attainable error limits of the measurements are discussed briefly. From surface excess isotherms furnished directly by experiment, the absolute amounts of substances contained in the adsorption layer can be derived only by using supplementary assumptions. As pointed out by the authors previously, some types of reduced surface excess isotherms exhibit a fairly long, practically linear section, and it was claimed that from the extrapolated intercepts of such sections the absolute amounts in question and, in favorable cases, the monolayer capacity may be computed. In view of possible criticisms, the foundations and limits of applicability of this claim are discussed in some more detail. It is shown further that simultaneous consideration of the course of relative adsorption can be very useful in some instances. A linearized representation proposed by Everett and others for determining monolayer capacity is discussed on an enlarged basis. Due warning is given against an uncritical use of any of the proposed methods.

Original languageEnglish
Pages (from-to)302-311
Number of pages10
JournalJournal of Colloid and Interface Science
Volume38
Issue number2
DOIs
Publication statusPublished - 1972

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Isotherms
Monolayers
isotherms
liquid phases
Adsorption
adsorption
Liquids
nonelectrolytes
Adsorption isotherms
Adsorbents
warning
adsorbents
estimating
liquids
Experiments

ASJC Scopus subject areas

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

Cite this

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abstract = "Any adsorption method for estimating surface areas of adsorbents is based on the determination of monolayer capacity. The present paper is concerned with the utilization of adsorption isotherms of mixtures of two completely miscible nonelectrolyte liquids for this purpose. Sufficient reliability and reproducibility of experimental isotherms being difficult to obtain, the main factors decisive in this respect and the normally attainable error limits of the measurements are discussed briefly. From surface excess isotherms furnished directly by experiment, the absolute amounts of substances contained in the adsorption layer can be derived only by using supplementary assumptions. As pointed out by the authors previously, some types of reduced surface excess isotherms exhibit a fairly long, practically linear section, and it was claimed that from the extrapolated intercepts of such sections the absolute amounts in question and, in favorable cases, the monolayer capacity may be computed. In view of possible criticisms, the foundations and limits of applicability of this claim are discussed in some more detail. It is shown further that simultaneous consideration of the course of relative adsorption can be very useful in some instances. A linearized representation proposed by Everett and others for determining monolayer capacity is discussed on an enlarged basis. Due warning is given against an uncritical use of any of the proposed methods.",
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N2 - Any adsorption method for estimating surface areas of adsorbents is based on the determination of monolayer capacity. The present paper is concerned with the utilization of adsorption isotherms of mixtures of two completely miscible nonelectrolyte liquids for this purpose. Sufficient reliability and reproducibility of experimental isotherms being difficult to obtain, the main factors decisive in this respect and the normally attainable error limits of the measurements are discussed briefly. From surface excess isotherms furnished directly by experiment, the absolute amounts of substances contained in the adsorption layer can be derived only by using supplementary assumptions. As pointed out by the authors previously, some types of reduced surface excess isotherms exhibit a fairly long, practically linear section, and it was claimed that from the extrapolated intercepts of such sections the absolute amounts in question and, in favorable cases, the monolayer capacity may be computed. In view of possible criticisms, the foundations and limits of applicability of this claim are discussed in some more detail. It is shown further that simultaneous consideration of the course of relative adsorption can be very useful in some instances. A linearized representation proposed by Everett and others for determining monolayer capacity is discussed on an enlarged basis. Due warning is given against an uncritical use of any of the proposed methods.

AB - Any adsorption method for estimating surface areas of adsorbents is based on the determination of monolayer capacity. The present paper is concerned with the utilization of adsorption isotherms of mixtures of two completely miscible nonelectrolyte liquids for this purpose. Sufficient reliability and reproducibility of experimental isotherms being difficult to obtain, the main factors decisive in this respect and the normally attainable error limits of the measurements are discussed briefly. From surface excess isotherms furnished directly by experiment, the absolute amounts of substances contained in the adsorption layer can be derived only by using supplementary assumptions. As pointed out by the authors previously, some types of reduced surface excess isotherms exhibit a fairly long, practically linear section, and it was claimed that from the extrapolated intercepts of such sections the absolute amounts in question and, in favorable cases, the monolayer capacity may be computed. In view of possible criticisms, the foundations and limits of applicability of this claim are discussed in some more detail. It is shown further that simultaneous consideration of the course of relative adsorption can be very useful in some instances. A linearized representation proposed by Everett and others for determining monolayer capacity is discussed on an enlarged basis. Due warning is given against an uncritical use of any of the proposed methods.

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