Journal article
Chemical speciation of environmentally significant metals with inorganic ligands. Part 5: The Zn2+ + OH–, Cl–, CO32–, SO42–, and PO43– systems (IUPAC Technical Report)
Pure and Applied Chemistry, Vol.85(12), pp.2249-2311
2013
Abstract
The numerical modeling of ZnII speciation amongst the environmental inorganic ligands Cl-, OH-, CO3 2-, SO4 2-, and PO4 3-requires reliable values for the relevant stability (formation) constants. This paper compiles and provides a critical review of these constants and related thermodynamic data. It recommends values of log10βp,q,r° valid at Im = 0 mol·kg-1 and 25 °C (298.15 K), and reports the empirical reaction ion interaction coefficients, Δ∈required to calculate log10βp,q,r values at higher ionic strengths using the Brønsted-Guggenheim-Scatchard specific ion interaction theory (SIT). Values for the corresponding reaction enthalpies, ΔrH, are reported where available. There is scope for additional high-quality measurements for the Zn2+ + H+ + CO3 2-system and for the Zn2+ + OH-and Zn2+ + SO4 2-systems at I > 0. In acidic and weakly alkaline fresh water systems (pH <8), in the absence of organic ligands (e.g., humic substances), ZnII speciation is dominated by Zn2+(aq). In this respect, ZnII contrasts with CuII and PbII (the subjects of earlier reviews in this series) for which carbonato-and hydroxido-complex formation become important at pH > 7. The speciation of ZnII is dominated by ZnCO3(aq) only at pH > 8.4. In seawater systems, the speciation at pH = 8.2 is dominated by Zn2+(aq) with ZnCl+, Zn(Cl)2(aq), ZnCO3(aq), and ZnSO4(aq) as minor species. This behaviour contrasts with that for CuII and PbII for which at the pH of seawater in equilibrium with the atmosphere at 25 °C (log10 {[H+]/c°} ≈ 8.2) the MCO3(aq) complex dominates over the MCln (2-n)+ species. The lower stability of the different complexes of ZnII compared with those of CuII, PbII, and CdII is also illustrated by the percentage of uncomplexed M2+ in seawater, which is ca. 55, 3, 2, and 3.3% of [MII]T, respectively.
Details
- Title
- Chemical speciation of environmentally significant metals with inorganic ligands. Part 5: The Zn2+ + OH–, Cl–, CO32–, SO42–, and PO43– systems (IUPAC Technical Report)
- Authors/Creators
- K.J. Powell (Author/Creator)P.L. Brown (Author/Creator)R.H. Byrne (Author/Creator)T. Gajda (Author/Creator)G. Hefter (Author/Creator)A-K Leuz (Author/Creator)S. Sjöberg (Author/Creator)H. Wanner (Author/Creator)
- Publication Details
- Pure and Applied Chemistry, Vol.85(12), pp.2249-2311
- Publisher
- International Union of Pure and Applied Chemistry
- Identifiers
- 991005540982507891
- Copyright
- © 2013 IUPAC.
- Murdoch Affiliation
- School of Veterinary and Life Sciences
- Language
- English
- Resource Type
- Journal article
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