Chemical speciation of environmentally significant metals with inorganic ligands Part 2: The Cu2+-OH-, Cl-, CO32-, SO42-, and PO43- systems (IUPAC Technical Report)

Powell, Kipton J.; Brown, Paul L.; Byrne, Robert H.; Gajda, Tamás; Hefter, Glenn; Sjöberg, Staffan; Wanner, Hans

doi:10.1351/pac200779050895

Pure Appl. Chem., 2007, Vol. 79, No. 5, pp. 895-950

http://dx.doi.org/10.1351/pac200779050895

ANALYTICAL CHEMISTRY DIVISION

Chemical speciation of environmentally significant metals with inorganic ligands Part 2: The Cu²⁺-OH^-, Cl^-, CO₃^2-, SO₄^2-, and PO₄^3- systems (IUPAC Technical Report)

Kipton J. Powell¹, Paul L. Brown², Robert H. Byrne³, Tamás Gajda⁴, Glenn Hefter⁵, Staffan Sjöberg⁶ and Hans Wanner⁷

¹ Department of Chemistry, University of Canterbury, Christchurch, New Zealand
² Rio Tinto Technical Services, 1 Research Avenue, Bundoora VIC3083, Australia
³ College of Marine Science, University of South Florida, 140 Seventh Avenue South, St. Petersburg, FL 33701-5016, USA
⁴ Department of Inorganic and Analytical Chemistry, A. József University, P.O. Box 440, Szeged 6701, Hungary
⁵ School of Mathematical and Physical Sciences, Murdoch University, Murdoch, WA 6150, Australia
⁶ Department of Inorganic Chemistry, Umeå University, S-901 87 Umeå, Sweden
⁷ Swiss Federal Nuclear Safety Inspectorate, CH-5232 Villigen, Switzerland

Abstract: Complex formation between Cu^II and the common environmental ligands Cl^-, OH^-, CO₃^2-, SO₄^2-, and PO₄^3- can have a significant effect on Cu^II speciation in natural waters with low concentrations of organic matter. Copper(II) complexes are labile, so the Cu^II distribution amongst these inorganic ligands can be estimated by numerical modeling if reliable values for the relevant stability (formation) constants are available. This paper provides a critical review of such constants and related thermodynamic data. It recommends values of log₁₀β_p,q,r° valid at I_m = 0 mol kg^-1 and 25 °C (298.15 K), along with the equations and specific ion interaction coefficients required to calculate log₁₀β_p,q,r values at higher ionic strengths. Some values for reaction enthalpies, ΔrHm, are also reported where available. In weakly acidic fresh water systems, in the absence of organic ligands, Cu^II speciation is dominated by the species Cu²⁺(aq), with CuSO₄(aq) as a minor species. In seawater, it is dominated by CuCO₃(aq), with Cu(OH)⁺, Cu²⁺(aq), CuCl⁺, Cu(CO₃)OH^-, Cu(OH)₂(aq), and Cu(CO₃)₂^2- as minor species. In weakly acidic saline systems, it is dominated by Cu²⁺(aq) and CuCl⁺, with CuSO₄(aq) and CuCl₂(aq) as minor species.