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Title: Solubility of B-Nb2O5 and the Hydrolysis of Niobium(V) in Aqueous Solution as a Function of Temperature and Ionic Strength

Abstract

B-Nb{sub 2}O{sub 5} was recrystallized from commercially available oxide, and XRD analyses indicated that it is stable in contact with solutions over the pH range 0 to 9, whereas solid polyniobates such as Na{sub 8}Nb{sub 6}O{sub 19} 13H{sub 2}O(s) appear to predominate at pH > 9. Solubilities of the crystalline B-Nb{sub 2}O{sub 5} were determined in five NaClO{sub 4} solutions (0.1 {le} Im/mol {center_dot} kg{sup -1} {le} 1.0) over a wide pH range at (25.0 {+-} 0.1) C and at 0.1 MPa. A limited number of measurements were also made at Im = 6.0 mol {center_dot} kg{sup -1}, whereas at Im = 1.0 mol {center_dot} kg{sup -1} the full range of pH was also covered at (10, 50 and 70) C. The pH of these solutions was fixed using either HClO{sub 4} (pH {le} 4) or NaOH (pH {ge} 10) and determined by mass balance, whereas the pH on the molality scale was measured in buffer mixtures of acetic acid + acetate (4 {le} pH {le} 6), Bis-Tris (pH {approx} 7), Tris (pH {approx} 8) and boric acid + borate (pH {approx} 9). Treatment of the solubility results indicated the presence of four species, Nb(OH){sub n}{sup 5-n} (where n =more » 4-7), so that the molal solubility quotients were determined according to: 0.5Nb{sub 2}O{sub 5}(cr) + 0.5(2n-5)H{sub 2}O(l){sup {center_dot}-} Nb(OH){sub n}{sup 5-n} + (n-5)H{sup +} (n = 4-7) and were fitted empirically as a function of ionic strength and temperature, including the appropriate Debye-Hueckel term. A Specific Interaction Theory (SIT) approach was also attempted. The former approach yielded the following values of log 10 K{sub sn} (infinite dilution) at 25 C: -(7.4 {+-} 0.2) for n = 4; -(9.1 {+-} 0.1) for n = 5; -(14.1 {+-} 0.3) for n = 6; and -(23.9 {+-} 0.6) for n = 7. Given the experimental uncertainties (2{sigma}), it is interesting to note that the effect of ionic strength only exceeded the combined uncertainties significantly in the case of log 10 K{sub s6} to I{sub m} = 1.0 mol {center_dot} kg{sup -1}, such that these values may be of use by defining their magnitudes in other media. Values of {Delta}{sub f} g{sup o}, {Delta}{sub f} H{sup o}, 5{sup o} and C{sub p}{sup o} (298.15 K, 0.1 MPa) for each hydrolysis product were calculated and tabulated.« less

Authors:
 [1];  [2];  [3];  [4]
  1. Nancy Universite, Vandoeuvre, France
  2. ORNL
  3. SPCTS, Limoges Cedex, France
  4. ANDRA, Chatenay-Malabry Cedex, France
Publication Date:
Research Org.:
Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
Sponsoring Org.:
USDOE Office of Science (SC)
OSTI Identifier:
1037167
DOE Contract Number:  
DE-AC05-00OR22725
Resource Type:
Journal Article
Journal Name:
Journal of Solution Chemistry
Additional Journal Information:
Journal Volume: 39; Journal Issue: 2; Journal ID: ISSN 0095-9782
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; ACETATES; ACETIC ACID; AQUEOUS SOLUTIONS; BORATES; BORIC ACID; BUFFERS; DILUTION; HYDROLYSIS; MASS BALANCE; MIXTURES; SOLUBILITY; X-RAY DIFFRACTION

Citation Formats

Peiffert, C, Nguyen-Trung, Chinh, Palmer, Donald, Laval, J P, and Giffaut, E. Solubility of B-Nb2O5 and the Hydrolysis of Niobium(V) in Aqueous Solution as a Function of Temperature and Ionic Strength. United States: N. p., 2010. Web. doi:10.1007/s10953-010-9495-z.
Peiffert, C, Nguyen-Trung, Chinh, Palmer, Donald, Laval, J P, & Giffaut, E. Solubility of B-Nb2O5 and the Hydrolysis of Niobium(V) in Aqueous Solution as a Function of Temperature and Ionic Strength. United States. doi:10.1007/s10953-010-9495-z.
Peiffert, C, Nguyen-Trung, Chinh, Palmer, Donald, Laval, J P, and Giffaut, E. Fri . "Solubility of B-Nb2O5 and the Hydrolysis of Niobium(V) in Aqueous Solution as a Function of Temperature and Ionic Strength". United States. doi:10.1007/s10953-010-9495-z.
@article{osti_1037167,
title = {Solubility of B-Nb2O5 and the Hydrolysis of Niobium(V) in Aqueous Solution as a Function of Temperature and Ionic Strength},
author = {Peiffert, C and Nguyen-Trung, Chinh and Palmer, Donald and Laval, J P and Giffaut, E},
abstractNote = {B-Nb{sub 2}O{sub 5} was recrystallized from commercially available oxide, and XRD analyses indicated that it is stable in contact with solutions over the pH range 0 to 9, whereas solid polyniobates such as Na{sub 8}Nb{sub 6}O{sub 19} 13H{sub 2}O(s) appear to predominate at pH > 9. Solubilities of the crystalline B-Nb{sub 2}O{sub 5} were determined in five NaClO{sub 4} solutions (0.1 {le} Im/mol {center_dot} kg{sup -1} {le} 1.0) over a wide pH range at (25.0 {+-} 0.1) C and at 0.1 MPa. A limited number of measurements were also made at Im = 6.0 mol {center_dot} kg{sup -1}, whereas at Im = 1.0 mol {center_dot} kg{sup -1} the full range of pH was also covered at (10, 50 and 70) C. The pH of these solutions was fixed using either HClO{sub 4} (pH {le} 4) or NaOH (pH {ge} 10) and determined by mass balance, whereas the pH on the molality scale was measured in buffer mixtures of acetic acid + acetate (4 {le} pH {le} 6), Bis-Tris (pH {approx} 7), Tris (pH {approx} 8) and boric acid + borate (pH {approx} 9). Treatment of the solubility results indicated the presence of four species, Nb(OH){sub n}{sup 5-n} (where n = 4-7), so that the molal solubility quotients were determined according to: 0.5Nb{sub 2}O{sub 5}(cr) + 0.5(2n-5)H{sub 2}O(l){sup {center_dot}-} Nb(OH){sub n}{sup 5-n} + (n-5)H{sup +} (n = 4-7) and were fitted empirically as a function of ionic strength and temperature, including the appropriate Debye-Hueckel term. A Specific Interaction Theory (SIT) approach was also attempted. The former approach yielded the following values of log 10 K{sub sn} (infinite dilution) at 25 C: -(7.4 {+-} 0.2) for n = 4; -(9.1 {+-} 0.1) for n = 5; -(14.1 {+-} 0.3) for n = 6; and -(23.9 {+-} 0.6) for n = 7. Given the experimental uncertainties (2{sigma}), it is interesting to note that the effect of ionic strength only exceeded the combined uncertainties significantly in the case of log 10 K{sub s6} to I{sub m} = 1.0 mol {center_dot} kg{sup -1}, such that these values may be of use by defining their magnitudes in other media. Values of {Delta}{sub f} g{sup o}, {Delta}{sub f} H{sup o}, 5{sup o} and C{sub p}{sup o} (298.15 K, 0.1 MPa) for each hydrolysis product were calculated and tabulated.},
doi = {10.1007/s10953-010-9495-z},
journal = {Journal of Solution Chemistry},
issn = {0095-9782},
number = 2,
volume = 39,
place = {United States},
year = {2010},
month = {1}
}