Zinc(II) oxide stability in alkaline sodium phosphate solutions at elevated temperatures

Technical Report · Thu Apr 01 00:00:00 EST 1993

DOI:https://doi.org/10.2172/10194886· OSTI ID:10194886

Ziemniak, S E; Opalka, E P

Zinc oxide (ZnO) is shown to transform into either of two phosphate-containing compounds in relatively dilute alkaline sodium phosphate solutions at elevated temperatures via ZnO(s) + Na{sup +} + H{sub 2}PO{sub 4}{sup {minus}} {r_reversible} NaZnPO{sub 4}(s) + H{sub 2}O or 2 ZnO(s) + H{sub 3}PO{sub 4}(aq) {r_reversible} Zn{sub 2}(OH)PO{sub 4}(s) + H{sub 2}O. X-ray diffraction analyses indicate that NaZnPO{sub 4} possesses an orthorhombic unit cell having lattice parameters a = 8.710 {+-} 0.013, b = 15.175 {+-} 0.010, and c = 8.027 {+-} 0.004 {angstrom}. The thermodynamic equilibria for these reactions were defined in the system ZnO-Na{sub 2}O-P{sub 2}O{sub 5}-H{sub 2}O for Na/P molar ratios between 2.1 and 3. Based on observed reaction threshold values for sodium phosphate concentration and temperature, the standard entropy (S{degrees}) and free energy of formation ({Delta}G{sub f}{degrees}) for NaZnPO{sub 4} were calculated to be 169.0 J/mol-K and {minus}1510.6 kJ/mol, respectively; similar values for Zn{sub 2}(OH)PO{sub 4} (tarbuttite) were 235.9 J/mol-K and {minus}1604.6 kJ/mol. Additions of sodium sulfite and sulfate did not alter the above reactions.

• Research Organization: Knolls Atomic Power Lab. (KAPL), Niskayuna, NY (United States)
• Sponsoring Organization: USDOE, Washington, DC (United States)
• DOE Contract Number: AC12-76SN00052
• OSTI ID: 10194886
• Report Number(s): KAPL-4762; ON: DE94003316; TRN: 93:004656
• Resource Relation: Other Information: PBD: Apr 1993
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
15 GEOTHERMAL ENERGY
ZINC OXIDES
CHEMICAL REACTIONS
CHEMICAL REACTION YIELD
X-RAY DIFFRACTION
THERMODYNAMIC PROPERTIES
ENTROPY
LATTICE PARAMETERS
STABILITY
AQUEOUS SOLUTIONS
SODIUM PHOSPHATES
THERMODYNAMICS
CORROSION
FORMATION FREE ENERGY
EXPERIMENTAL DATA
TEMPERATURE DEPENDENCE
Geothermal Legacy
400201
152001
CHEMICAL AND PHYSICOCHEMICAL PROPERTIES
PROPERTIES OF AQUEOUS SOLUTIONS