Chemical speciation of environmentally significant metals with inorganic ligands. Part 5: The Zn²⁺ + OH^-, Cl^-, CO₃ ^2-, SO₄ ^2-, and PO₄ ^3- systems (IUPAC Technical Report)

Abstract

Abstract:The numerical modeling of Zn II speciation amongst the environmental inorganic ligands Cl -, OH -, CO 3 2-, SO 4 2-, and PO 4 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 log 10 β p,q,r°v alid at I m = 0 molؒkg -1 and 25 °C (298.15 K), and reports the empirical reaction ion interaction coefficients, Δε, required to calculate log 10 β p,q,r values at higher ionic strengths using the Brønsted-Guggenheim-Scatchard specific ion interaction theory (SIT). Values for the corresponding reaction enthalpies, Δ r H, are reported where available. There is scope for additional high-quality measurements for the Zn 2+ + H + + CO 3 2-system and for the Zn 2+ + OH -and Zn 2+ + SO 4 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), Zn II speciation is dominated by Zn 2+ (aq). In this respect, Zn II contrasts with Cu II and Pb II (the subjects of earlier reviews in this series) for which carbonato-and hydroxido-complex formation become important at pH > 7. The speciation of Zn II is dominated by ZnCO 3 (aq) only at pH > 8.4.In seawater systems, the speciation at pH = 8.2 is dominated by Zn 2+ (aq) with ZnCl + , Zn(Cl) 2 (aq), ZnCO 3 (aq), and ZnSO 4 (aq) as minor species. This behaviour contrasts with that for Cu II and Pb II for which at the pH of seawater in equilibrium with the atmosphere at 25 °C (log 10 {[H + ]/c°} ≈ 8.2) the MCO 3 (aq) complex dominates over the MCl n (2-n)+ species. The lower stability of the different complexes of Zn II compared with those of Cu II , Pb II , and Cd II is also illustrated by the percentage of uncomplexed M 2+ in seawater, which is ca. 55, 3, 2, and 3.3 % of [M II ] T , respectively.

Influences of temperature and salinity on physicochemical properties and toxicity of zinc oxide nanoparticles to the marine diatom Thalassiosira pseudonana

“…Previous studies showed that solubility of ZnO was less than 1 mg/L at 35 °C while at 15 °C it was 3.5 mg/L 26 . At higher salinity, when released from ZnO or ZnO-NPs, Zn 2+ can form complexes with the abundant anions (e.g., Cl − and SO 4 2− ) in seawater which would reduce the concentration of free Zn 2+ ions 27 . Concentrations of dissolved zinc in the test suspension of ZnO were less than that in ZnO-NPs because ZnO has significantly larger sizes of particles (Fig.…”

“…At greater salinities, due to complexation of zinc ions (Zn 2+ ) with other anion present in seawater, amounts of bioavailable Zn 2+ would be less 27 . The 96-h LC50s of ZnO-NPs for the marine copepod Tigriopus japonicus were 1.22 mg/L and 2.44 mg/L at salinities of 5 and 35 ppt, respectively 8 .…”

Chemical Thermodynamics and Calculation of Parameters of Ionic Equilibria of Indium(III) in Perchlorate, Chloride and Sulphate Aqueous Solutions

“…Модель Бренстеда-Гуггенгейма-Скэтчарда, получившая название «теория специфического взаимодействия» (Specific ion Interaction Theory, сокращенно SIT) и рекомендованная ИЮПАК для экстраполяции констант устойчивости комплексов на нулевую ионную силу раствора (бесконечное разбавление) [31,35,36], является наиболее простой и хорошо проработанной. Применение строгой модели К.С.…”

“…Энтальпия реакции комплексообразования является функцией не только температуры, но и ионной силы раствора [29,44,35,36,118]…”

Development of the application of speciation in chemistry

“…In speciation calculations, sorting the most feasible interactions and associations present in solutions as well as selecting their stability constants from published data can significantly affect the final predicted distribution. Several computer programs have been developed and employed to calculate the concentrations of various chemical species at equilibrium based on a database of equilibrium stability constants for inorganic species encountered in water [104]. In addition to the formation of different metal-ligand complexes, the equilibria between soluble and insoluble phases, as well as the adsorption of colloids must be considered during computational modeling.…”