Thermodynamic Model for SnO₂(cr) and SnO₂(am) Solubility in the Aqueous Na+-H+ -OH- -Cl- -H₂O System

Journal Article · Sat Jul 16 00:00:00 EDT 2011 · Journal of Solution Chemistry

DOI:https://doi.org/10.1007/s10953-011-9723-1· OSTI ID:1021829

Rai, Dhanpat ^[1]; Yui, Mikazu ^[2]; Schaef, Herbert T. ^[3]; Kitamura, Akira ^[2]

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1. Rai Enviro-Chem, LLC, Yachats, OR (United States)
2. Japan Atomic Energy Agency (JAEA), Tokai (Japan)
3. Pacific Northwest National Lab. (PNNL), Richland, WA (United States)

The solubility of SnO₂(cassiterite) was studied at 23 ± 2°C as functions of time (7 – 49 days) and pH value (0-14.5). Steady state concentrations were reached in < 7 days. The data were interpreted using the SIT model. The data shows that SnO₂(cassiterite) is the stable phase at pH values of < ~11.7. These extensive data provided a log10 K⁰ value of -64.39 ± 0.30 for the reaction (SnO₂(cassiterite) + 2H₂O = Sn⁴⁺ + 4OH^-) and values of 1.86 ± 0.30, ≤ -0.62, -9.20 ± 0.34, and -20.28 ± 0.34 for the reaction (Sn⁴⁺ + nH₂O = Sn(OH)n^4-n + nH⁺) with values of “n” equal to 1, 4, 5, and 6 respectively. These thermodynamic hydrolysis constants were used to reinterpret the extensive literature data for SnO₂(am) solubility, which provided a log10 K⁰ value of -61.80 ± 0.29 for the reaction (SnO₂(am) + 2H₂O = Sn⁴⁺ + 4OH^-). SnO₂(cassiterite) is unstable under highly alkaline conditions (NaOH concentrations > 0.003 mol.dm^-3) and transforms to a double salt of SnO₂ and NaOH. Although additional well-focused studies will be required for confirmation, the experimental data in the highly alkaline region (0.003 to 3.5 mol.dm^-3 NaOH) can be well described with log10 K⁰ of -5.29 ± 0.35 for the reaction (Na₂Sn(OH)₆(s) = Na₂Sn(OH)₆(aq)).

• Research Organization: Pacific Northwest National Laboratory (PNNL), Richland, WA (United States)
• Sponsoring Organization: USDOE
• DOE Contract Number: AC05-76RL01830
• OSTI ID: 1021829
• Report Number(s): PNNL-SA--76900
• Journal Information: Journal of Solution Chemistry, Journal Name: Journal of Solution Chemistry Journal Issue: 7 Vol. 40; ISSN 0095-9782; ISSN JSLCAG
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
HYDROLYSIS
PH VALUE
SOLUBILITY
Sn
SnO2(am)
THERMODYNAMIC MODEL
THERMODYNAMICS
Tin hydroxide
cassiterite
hydrolysis constants of tin
solubility
thermodynamic data
tin