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

Abstract

Complex formation between CuII and the common environmental ligands Cl-, OH-, CO32-, SO42-, and PO43- can have a significant effect on CuII speciation in natural waters with low concentrations of organic matter. Copper(II) complexes are labile, so the CuII 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 log10βp,q,r° valid at Im = 0 mol kg-1 and 25 °C (298.15 K), along with the equations and specific ion interaction coefficients required to calculate log10βp,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, CuII 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)22- 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.

Copper(II) Catalysis of Water Oxidation

“…The extent of the blue shift in CO 2 /HCO 3 À /CO 3 2À aqueous solutions at different pHs in Figure S15 is consistent with the coordination by CO 3 2À that is dominant at high pH and the coordination by HCO 3 À that is dominant at low pH. A calculated speciation diagram for the ternary Cu II -bicarbonate/carbonate system [28] is consistent with this conclusion, although it was modeled at much lower Cu II (10 À9 m) and carbonate (f(CO 2 ) = 10 1.5 Pa) concentrations. Based on the results of an earlier pulsed electron paramagnetic resonance (EPR) study, [29] the dominant species in solutions which are closer to the catalytic conditions are monodentate/bidentate complexes with HCO 3 À /CO 3 2À as ligands; depending on the pH, the remaining coordination sites are occupied by aqua or hydroxo ligands.…”

Low temperature one‐step synthesis of poly(barbituric acid) functionalized magnetic nanoparticles for removal of heavy metal ions

“…The formation of precipitation of metal hydroxides must be taken into account as well . In the case of Pb (II) and Cu (II) ions, the slight decrease of adsorption in the range of pH 6–7 can be explained by the formation of hydroxide complexes (Pb(OH) + , Cu(OH) + ) due to the equilibrium constants (logK Pb(OH) + and Cu(OH) + are −7.46 and −7.95 at 25°C, respectively) . For Pb (II) and Cu (II) ions, one can calculate that Pb (II) ions are partially hydrolyzed at pH 8.2 and Cu (II) ions at pH 6.4.…”

Copper Containing Molecular Systems in Electrocatalytic Water Oxidation—Trends and Perspectives

“…A common feature of the above discussed, purely inorganic molecular systems is the high concentration of the coordinating oxyanion that is always necessary owing to the low solubility of the stoichiometric Cu-oxyanion compounds [27]. On the other hand, if organic chelators are applied as supporting ligands instead of the inorganic anions high excess is not a requirement anymore.…”