Solid-liquid partitioning and speciation of Pb(II) and Cd(II) on goethite under high pH conditions, as examined by subnanomolar heavy metal analysis, X-ray absorption spectroscopy, and surface complexation modeling.

Autor: Takeda N; Division of Natural System, Graduate School of Natural Science, Kanazawa University, Kakuma, Kanazawa, Ishikawa, 920-1192, Japan., Fukushi K; Institute of Nature and Environmental Technology, Kanzawa University, Kakuma, Kanazawa, Ishikawa, 920-1192, Japan. Electronic address: fukushi@staff.kanazawa-u.ac.jp., Okuyama A; Division of Natural System, Graduate School of Natural Science, Kanazawa University, Kakuma, Kanazawa, Ishikawa, 920-1192, Japan., Takahashi Y; Department of Earth and Planetary Science, The University of Tokyo, 7-3-1 Hongo, Tokyo, 113-0033, Japan.
Jazyk: angličtina
Zdroj: Chemosphere [Chemosphere] 2024 Sep; Vol. 363, pp. 142766. Date of Electronic Publication: 2024 Jul 04.
DOI: 10.1016/j.chemosphere.2024.142766
Abstrakt: The adsorption of heavy metals on iron oxides generally increases with pH and is almost complete at neutral to slightly alkaline pH. However, almost complete adsorption on a linear scale does not imply sufficient removal of the heavy metals in terms of their toxicity. Here, we elucidated the chemical reactions that determine the solid-liquid partitioning of Pb(II) and Cd(II) on goethite at high pH. While the removal of both heavy metals was almost complete on a linear scale above pH 7 for Pb(II) and pH 9 for Cd(II), the dissolved metal concentrations decreased on a logarithmic scale with pH, reaching minima at around pH 10 for Pb(II) and pH 10-11 for Cd(II), and then they increased with pH thereafter. The XAFS spectra of Pb(II)- or Cd(II)-adsorbed goethite prepared at pH > 11 were almost the same as those at neutral pH, suggesting that removal of the heavy metals from solution was achieved by a single adsorption reaction over the entire pH range. Based on the observed macroscopic and microscopic adsorption behaviors at high pH, a robust surface complexation model was developed to predict the solid-liquid partitioning of divalent heavy metals over the entire pH range.
Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
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Databáze: MEDLINE