Modeling the acid-base properties of molybdate(VI) in different ionic media, ionic strengths and temperatures, by EDH, SIT and Pitzer equations

Alberto Pettignano, Demetrio Milea, Silvio Sammartano, Concetta De Stefano, Francesco Crea, Anna Irto

Research output: Contribution to journalArticle

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Abstract

This paper reports the results of a study on the determination of the protonation constants of MoO42 −, in NaClaq, NaNO3aq, KClaq, at different ionic strengths (0 < I/mol dm− 3 ≤ 5.0 in NaClaq, 0 < I/mol dm− 3 ≤ 3.0 in NaNO3aq and KClaq) and temperatures (278.15 ≤ T/K ≤ 318.15 in NaClaq, only 298.15 K in NaNO3aq and KClaq), by potentiometric (ISE-H+ glass electrode) and spectrophotometric (UV/Vis) titrations. After a critical analysis of results and literature findings, the proposed speciation model takes into account the formation of two monomeric and four heptameric species, namely: MoO4H−, MoO4H2, (MoO4)7H86 −, (MoO4)7H95 −, (MoO4)7H104 − and (MoO4)7H113 −. Due to the complexity of the system, and to discrepancies of literature findings, particular attention has been paid to the determination of the stability of monomeric species, by performing measurements at very low concentrations, in which the polymerization processes do not occur. Data obtained have then been used to model the dependence of the acid-base properties of molybdate on medium, ionic strength and temperature by models commonly used for these purposes, namely the Extended Debye-Hückel (EDH), the classical Specific ion Interaction Theory (SIT), Pitzer equations, and van't Hoff (for the dependence on temperature). These last results, some of them obtained for the first time in this work, can be exploited for the modeling of the speciation of MoO42 − in a wide range of conditions typical of natural waters and biological fluids, as well as in many aqueous systems of technological/industrial importance, where molybdate can play key roles.
Original languageEnglish
Pages (from-to)15-26
Number of pages12
JournalJournal of Molecular Liquids
Volume229
Publication statusPublished - 2017

Fingerprint

molybdates
Ionic strength
Ions
acids
Acids
glass electrodes
ions
Protonation
interactions
trucks
Titration
titration
Temperature
temperature
low concentrations
polymerization
Polymerization
Glass
Electrodes
Fluids

All Science Journal Classification (ASJC) codes

  • Electronic, Optical and Magnetic Materials
  • Materials Chemistry
  • Physical and Theoretical Chemistry
  • Spectroscopy
  • Condensed Matter Physics
  • Atomic and Molecular Physics, and Optics

Cite this

Modeling the acid-base properties of molybdate(VI) in different ionic media, ionic strengths and temperatures, by EDH, SIT and Pitzer equations. / Pettignano, Alberto; Milea, Demetrio; Sammartano, Silvio; De Stefano, Concetta; Crea, Francesco; Irto, Anna.

In: Journal of Molecular Liquids, Vol. 229, 2017, p. 15-26.

Research output: Contribution to journalArticle

Pettignano, Alberto ; Milea, Demetrio ; Sammartano, Silvio ; De Stefano, Concetta ; Crea, Francesco ; Irto, Anna. / Modeling the acid-base properties of molybdate(VI) in different ionic media, ionic strengths and temperatures, by EDH, SIT and Pitzer equations. In: Journal of Molecular Liquids. 2017 ; Vol. 229. pp. 15-26.
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abstract = "This paper reports the results of a study on the determination of the protonation constants of MoO42 −, in NaClaq, NaNO3aq, KClaq, at different ionic strengths (0 < I/mol dm− 3 ≤ 5.0 in NaClaq, 0 < I/mol dm− 3 ≤ 3.0 in NaNO3aq and KClaq) and temperatures (278.15 ≤ T/K ≤ 318.15 in NaClaq, only 298.15 K in NaNO3aq and KClaq), by potentiometric (ISE-H+ glass electrode) and spectrophotometric (UV/Vis) titrations. After a critical analysis of results and literature findings, the proposed speciation model takes into account the formation of two monomeric and four heptameric species, namely: MoO4H−, MoO4H2, (MoO4)7H86 −, (MoO4)7H95 −, (MoO4)7H104 − and (MoO4)7H113 −. Due to the complexity of the system, and to discrepancies of literature findings, particular attention has been paid to the determination of the stability of monomeric species, by performing measurements at very low concentrations, in which the polymerization processes do not occur. Data obtained have then been used to model the dependence of the acid-base properties of molybdate on medium, ionic strength and temperature by models commonly used for these purposes, namely the Extended Debye-H{\"u}ckel (EDH), the classical Specific ion Interaction Theory (SIT), Pitzer equations, and van't Hoff (for the dependence on temperature). These last results, some of them obtained for the first time in this work, can be exploited for the modeling of the speciation of MoO42 − in a wide range of conditions typical of natural waters and biological fluids, as well as in many aqueous systems of technological/industrial importance, where molybdate can play key roles.",
author = "Alberto Pettignano and Demetrio Milea and Silvio Sammartano and {De Stefano}, Concetta and Francesco Crea and Anna Irto",
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TY - JOUR

T1 - Modeling the acid-base properties of molybdate(VI) in different ionic media, ionic strengths and temperatures, by EDH, SIT and Pitzer equations

AU - Pettignano, Alberto

AU - Milea, Demetrio

AU - Sammartano, Silvio

AU - De Stefano, Concetta

AU - Crea, Francesco

AU - Irto, Anna

PY - 2017

Y1 - 2017

N2 - This paper reports the results of a study on the determination of the protonation constants of MoO42 −, in NaClaq, NaNO3aq, KClaq, at different ionic strengths (0 < I/mol dm− 3 ≤ 5.0 in NaClaq, 0 < I/mol dm− 3 ≤ 3.0 in NaNO3aq and KClaq) and temperatures (278.15 ≤ T/K ≤ 318.15 in NaClaq, only 298.15 K in NaNO3aq and KClaq), by potentiometric (ISE-H+ glass electrode) and spectrophotometric (UV/Vis) titrations. After a critical analysis of results and literature findings, the proposed speciation model takes into account the formation of two monomeric and four heptameric species, namely: MoO4H−, MoO4H2, (MoO4)7H86 −, (MoO4)7H95 −, (MoO4)7H104 − and (MoO4)7H113 −. Due to the complexity of the system, and to discrepancies of literature findings, particular attention has been paid to the determination of the stability of monomeric species, by performing measurements at very low concentrations, in which the polymerization processes do not occur. Data obtained have then been used to model the dependence of the acid-base properties of molybdate on medium, ionic strength and temperature by models commonly used for these purposes, namely the Extended Debye-Hückel (EDH), the classical Specific ion Interaction Theory (SIT), Pitzer equations, and van't Hoff (for the dependence on temperature). These last results, some of them obtained for the first time in this work, can be exploited for the modeling of the speciation of MoO42 − in a wide range of conditions typical of natural waters and biological fluids, as well as in many aqueous systems of technological/industrial importance, where molybdate can play key roles.

AB - This paper reports the results of a study on the determination of the protonation constants of MoO42 −, in NaClaq, NaNO3aq, KClaq, at different ionic strengths (0 < I/mol dm− 3 ≤ 5.0 in NaClaq, 0 < I/mol dm− 3 ≤ 3.0 in NaNO3aq and KClaq) and temperatures (278.15 ≤ T/K ≤ 318.15 in NaClaq, only 298.15 K in NaNO3aq and KClaq), by potentiometric (ISE-H+ glass electrode) and spectrophotometric (UV/Vis) titrations. After a critical analysis of results and literature findings, the proposed speciation model takes into account the formation of two monomeric and four heptameric species, namely: MoO4H−, MoO4H2, (MoO4)7H86 −, (MoO4)7H95 −, (MoO4)7H104 − and (MoO4)7H113 −. Due to the complexity of the system, and to discrepancies of literature findings, particular attention has been paid to the determination of the stability of monomeric species, by performing measurements at very low concentrations, in which the polymerization processes do not occur. Data obtained have then been used to model the dependence of the acid-base properties of molybdate on medium, ionic strength and temperature by models commonly used for these purposes, namely the Extended Debye-Hückel (EDH), the classical Specific ion Interaction Theory (SIT), Pitzer equations, and van't Hoff (for the dependence on temperature). These last results, some of them obtained for the first time in this work, can be exploited for the modeling of the speciation of MoO42 − in a wide range of conditions typical of natural waters and biological fluids, as well as in many aqueous systems of technological/industrial importance, where molybdate can play key roles.

UR - http://hdl.handle.net/10447/226452

M3 - Article

VL - 229

SP - 15

EP - 26

JO - Journal of Molecular Liquids

JF - Journal of Molecular Liquids

SN - 0167-7322

ER -