Solid-Solute Phase Equilibria in Aqueous Solution. XII. Solubility and Thermal Decomposition of Smithsonite期刊界 All Journals 搜尽天下杂志传播学术成果专业期刊搜索期刊信息化学术搜索

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Solid-Solute Phase Equilibria in Aqueous Solution. XII. Solubility and Thermal Decomposition of Smithsonite

Authors:	Wolfgang Preis Erich Königsberger Heinz Gamsjäger

Abstract:	The solubility constant of ZnCO₃, smithsonite, in aqueous NaClO₄ solutions hasbeen investigated as a function of temperature (288.15 T/K 338.15) atconstant ionic strength I = 1.00 mol-kg^–1. In addition, the solubility of zinccarbonate has been determined at 2.00 and 3.00 mol-kg^–1 NaClO₄ (298.15 K).The solubility measurements have been evaluated by applying the Daviesapproximation, the specific ion-interaction theory, and the Pitzer model, respectively.The thermodynamic interpretation leads to an internally consistent set ofthermodynamic data for ZnCO₃ (298.15 K): solubility constant log*K _p50 ⁰ = 7.25 ± 0.10,standard Gibbs energy of formation _i G (ZnCO₃) = (–777.3±0.6)kJ-mol^–1, standard enthalphy of formation _f H (ZnCO₃)= (–820.2±3.0) kJ-mol^–1,and standard entropy S (ZnCO₃) = (77±10)J-mol^–1 K.^–1. Furthermore, the DSCcurve for the thermal decarbonation of zinc carbonate has been recorded in orderto obtain the enthalpy of formation _fH (ZnCO₃) =(–820.2±2.0) from theheat of decomposition. Finally, our results are also consistent within theexperimental error limits with a recent determination of the standard entropy ofsmithsonite, leading to a recommended set of thermodynamic properties of ZnCO₃: $\begin{gathered} \Delta _f G^\Theta ({\text{ZnCO}}_{\text{3}} ) = ( - 737.3 \pm 0.6){\text{kJ - mol}}^{{\text{ - 1}}} \hfill \\ \Delta _f H^\Theta ({\text{ZnCO}}_{\text{3}} ) = ( - 818.9 \pm 0.6){\text{kJ - mol}}^{{\text{ - 1}}} \hfill \\ {\text{ }}S^\Theta ({\text{ZnCO}}_{\text{3}} ) = (81.2 \pm 0.2){\text{J - mol}}^{{\text{ - 1}}} - {\text{K}}^{{\text{ - 1}}} \hfill \\ \end{gathered}$

Keywords:	Solubility temperature dependence carbonate zinc smithsonite Pitzer model Davies approximation specific ion-interaction theory thermalanalysis DSC
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