Adsorption of polyprotic acid at the water/air interface: Effect of counter ion and pH on surface activity of FeIII-EDTA complex

Masumi Villeneuve, Mihoko Tanaka, Mayuko Abe, Hiroyasu Sakamoto, Yoshiteru Hayami

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A rigorous thermodynamic treatment appropriate for surface adsorption from mixed aqueous solution of alkali and polyprotic acid was derived. Those equations were applied to mixed aqueous solution/air systems of alkali metal hydroxide and FeIII complex with ethylenediamine- N, N, N′,N′-tetraacetate (Fe-EDTA). Surface density of each species arising from Fe-EDTA was separately evaluated, and thus, surface activity of Fe-EDTA was studied, especially its dependence on pH and how it is influenced by the counter cations. Fe-EDTA was positively adsorbed at the water/air interface at very low pHs and negatively at high pHs. The pH range of positive adsorption of Fe-EDTA with potassium ion, as a counter ion, was wider than that with sodium ion. Thus, potassium ion, a structure breaker, tended to smooth surface adsorption of Fe-EDTA at the water/air interface, whereas sodium ion, a structure maker, tended to withdraw Fe-EDTA from the interfacial region.

Original languageEnglish
Pages (from-to)2335-2348
Number of pages14
JournalColloid and Polymer Science
Issue number9
Publication statusPublished - Sep 2014


All Science Journal Classification (ASJC) codes

  • Physical and Theoretical Chemistry
  • Polymers and Plastics
  • Colloid and Surface Chemistry
  • Materials Chemistry

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