Copper complexation by tannic acid in aqueous solution

Peter Kraal*, Boris Jansen, Klaas G J Nierop, Jacobus M. Verstraten

*Corresponding author for this work

Research output: Contribution to journalArticleAcademicpeer-review

Abstract

The speciation of titrated copper in a dissolved tannic acid (TA) solution with an initial concentration of 4 mmol organic carbon (OC)/l was investigated in a nine-step titration experiment (Cu/OC molar ratio = 0.0030-0.0567). We differentiated between soluble and insoluble Cu species by 0.45 μm filtration. Measurements with a copper ion selective electrode (ISE) and diffusive gradients in thin films (DGT) were conducted to quantify unbound Cu(II) cations ('free' Cu) and labile soluble Cu complexes. For the DGT measurements, we used an APA hydrogel and a Chelex 100 chelating resin (Na form). Insoluble organic Cu complexes (>0.45 μm) was the dominant Cu species for Cu/OC = 0.0030-0.0567 with a maximum fraction of 0.96 of total Cu. At Cu/OC > 0.0100, Cu-catalysed degradation of aggregate structures resulted in a strong increase of free Cu and (labile) soluble Cu complexes with a maximum fraction of 0.28 and 0.32 of total Cu, respectively. Labile (i.e. DGT-detectable) soluble Cu complexes had a relatively high averaged diffusion coefficient (D) in the APA hydrogel (3.50 × 10-6- 5.58 × 10-6 cm2 s-1).

Original languageEnglish
Pages (from-to)2193-2198
Number of pages6
JournalChemosphere
Volume65
Issue number11
DOIs
Publication statusPublished - Dec 2006

Keywords

  • Copper ion selective electrode (ISE)
  • Copper speciation
  • Diffusive gradients in thin films (DGT)
  • Tannin

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