Zinc(II) oxide solubility and phase behavior in aqueous sodium phosphate solutions at elevated temperatures |
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Authors: | S. E. Ziemniak M. E. Jones K. E. S. Combs |
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Affiliation: | (1) Knolls Atomic Power Laboratory, P. O. Box 1072, 12301-1072 Schenectady, NY |
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Abstract: | A platinum-lined, flowing autoclave facility is used to investigate the solubility/phase behavior of zinc(II) oxide in aqueous sodium phosphate solutions at temperatures between 17 and 287°C. ZnO solubilities are observed to increase continuously with temperature and phosphate concentration. At higher phosphate concentrations, a solid phase transformation to NaZnPO4 is observed. NaZnPO4 solubilities are retrograde with temperature. The measured solubility behavior is examined via a Zn(II) ion hydrolysis/complexing model and thermodynamic functions for the hydrolysis/complexing reaction equilibria are obtained from a least-squares analysis of the data. The existence of two new zinc(II) ion complexes, Zn(OH)2(HPO4)2– and Zn(OH)3(H2PO4)2–, is reported for the first time. A summary of thermochemical properties for species in the systems ZnO–H2O and ZnO–Na2O–P2O5–H2O is also provided. |
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Keywords: | Zinc oxide aqueous solutions metal ion hydrolysis phosphato-complexing equilibrium constant thermodynamics pressurized water hydrothermal solutions corrosion |
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