Modeling of the complex formation of metal ions with humic acids

Osamu Tochiyama, Yuichi Niibori, Kouichi Tanaka, Takumi Kubota, Hirofumi Yoshino, Akira Kirishima, Budi Setiawan

Research output: Contribution to journalArticlepeer-review

18 Citations (Scopus)


Based on the conceptual model of cation-humic interactions considering the heterogeneous composition and polyelectrolyte nature of humic acids, the description of the interaction by the expression, log Kapp = log K - m log [M] + a log α b log [Na+], is proposed, where K app = [M··(zR)]/([M][R]), [M··(zR)] is the concentration of the cation bound to the humic acid, [M] is the concentration of the free cation with charge z, and [R] is the concentration of the free anionic sites of the humic acid, [R] = (CR - z[M··(zR)])α (CR is a total concentration of proton exchanging sites and α is a degree of dissociation), log K, m, a and b are the constant parameters depending on the cation and the humic acid. The expression is successfully applied to the experimental results on the complex formation (or protonation) of humate and polyacrylate (a homogeneous polymeric weak acid) with H+, NpO2+, Eu3+, Ca2+, Fe2+ and Fe3+ obtained under the condition where hydrolysis of cations and saturation of the reacting sites can be neglected.

Original languageEnglish
Pages (from-to)559-565
Number of pages7
JournalRadiochimica Acta
Issue number9-11
Publication statusPublished - 2004


  • Complex formation
  • Heterogeneity
  • Humic acid
  • Modeling
  • Polyelectrolyte


Dive into the research topics of 'Modeling of the complex formation of metal ions with humic acids'. Together they form a unique fingerprint.

Cite this