Specific adsorption of simple organic acids on metal(hydr)oxides

A radiotracer approach

Research output: Contribution to journalArticle

17 Citations (Scopus)

Abstract

The pH dependence of adsorption of 14C-labeled benzoic and oxalic acids on γ-Al2O3 and hematite was studied in acid medium in the presence of 0.5 mol dm-3 NaClO4 supporting electrolyte. It was found that the adsorption of the organic species starts at pH values where the protonation of the oxide surface takes place. In the case of benzoic acid the extent of adsorption with decreasing pH goes through a sharp maximum at a pH value not far from the pK (4.2) of the acid, while in the case of oxalic acid only a small decrease can be observed at very low pH values (pH <1). In indirect radiotracer studies using 35S-labeled sulfate ions it was shown that the competitive adsorption of formic, malonic, maleic, and oxalic acids with sulfate ions depends on pH and the effect of the organic acid on the anion adsorption becomes pronounced at pH values about and above the pK of the acid. On the basis of these observations and considerations concerning the dissociation of the organic acids studied it is assumed that the specific adsorption of the anionic form of the acids takes place. It is, however, emphasized that the negative charge of the anions, consequently the electrostatic forces, do not play significant role in the adsorption.

Original languageEnglish
Pages (from-to)214-221
Number of pages8
JournalJournal of Colloid and Interface Science
Volume254
Issue number2
DOIs
Publication statusPublished - 2002

Fingerprint

Organic acids
Oxides
metal oxides
Metals
Adsorption
acids
adsorption
Oxalic acid
oxalic acid
Acids
Oxalates
Benzoic acid
benzoic acid
Sulfates
Anions
Negative ions
sulfates
Ions
Oxalic Acid
Benzoic Acid

Keywords

  • γ-AlO
  • C-labeled benzoic and oxalic acids
  • Formic, malonic and maleic acids
  • Hematite
  • Labeled HSO
  • Radiotracer study
  • Specific adsorption

ASJC Scopus subject areas

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

Cite this

Specific adsorption of simple organic acids on metal(hydr)oxides : A radiotracer approach. / Horányi, G.

In: Journal of Colloid and Interface Science, Vol. 254, No. 2, 2002, p. 214-221.

Research output: Contribution to journalArticle

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