Solubility of Rhodochrosite (MnCO3) in NaCl Solutions

Yanxin Luo, Frank J Millero

Research output: Contribution to journalArticle

8 Citations (Scopus)

Abstract

The solubility of rhodochrosite (MnCO3) at 25°C under constant carbon dioxide partial pressure p(CO2) was determined in NaCl solutions as a function of ionic strength I. The dissolution of MnCO 3(s) for the reaction MnCO3(s) + 2H+ = Mn 2+ + CO2(g) + H2O Kso* = [Mn2+]p(CO2)/[H+]2 has been determined as a function of pH. From these values, we have determined the equilibrium constant for the stoichiometric solubility of MnCO3(s) in NaCl solutions Ksp* = [Mn2+]T[CO 3 2-]T These values have been fitted to the equation log Ksp* = -10.3 + 2.39 I0.5 - 0.69 I with a standard error of σ = 0.1 with I and concentrations in molalities. The extrapolated value of log Ksp o (-10.3) in water is in good agreement with literature data (-10.1 to 10.8) determined in solutions of different composition and ionic strength. The measured values of the activity coefficient, γT(Mn2+) and γ T(CO3 2-), have been used to estimate the stability constant for the formation of the MnCO3 ion pair, K* (MnCO3 0). The value of K0(MnCO3 0) calculated from the values of K* (MnCO3) by the Pitzer equation (σ = 0.1) in this study (4.8 ± 0.1) is in reasonable agreement with literature data.

Original languageEnglish (US)
Pages (from-to)405-416
Number of pages12
JournalJournal of Solution Chemistry
Volume32
Issue number5
DOIs
StatePublished - May 2003

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Solubility
solubility
Ionic strength
Osmolar Concentration
Partial Pressure
Activity coefficients
Equilibrium constants
Carbon Monoxide
Carbon Dioxide
Partial pressure
partial pressure
carbon dioxide
dissolving
Dissolution
Ions
Water
coefficients
estimates
Chemical analysis
water

Keywords

  • Activity coefficients
  • Pitzer equations
  • Rhodochrosite
  • Sodium chloride
  • Solubility

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry

Cite this

Solubility of Rhodochrosite (MnCO3) in NaCl Solutions. / Luo, Yanxin; Millero, Frank J.

In: Journal of Solution Chemistry, Vol. 32, No. 5, 05.2003, p. 405-416.

Research output: Contribution to journalArticle

Luo, Yanxin ; Millero, Frank J. / Solubility of Rhodochrosite (MnCO3) in NaCl Solutions. In: Journal of Solution Chemistry. 2003 ; Vol. 32, No. 5. pp. 405-416.
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N2 - The solubility of rhodochrosite (MnCO3) at 25°C under constant carbon dioxide partial pressure p(CO2) was determined in NaCl solutions as a function of ionic strength I. The dissolution of MnCO 3(s) for the reaction MnCO3(s) + 2H+ = Mn 2+ + CO2(g) + H2O Kso* = [Mn2+]p(CO2)/[H+]2 has been determined as a function of pH. From these values, we have determined the equilibrium constant for the stoichiometric solubility of MnCO3(s) in NaCl solutions Ksp* = [Mn2+]T[CO 3 2-]T These values have been fitted to the equation log Ksp* = -10.3 + 2.39 I0.5 - 0.69 I with a standard error of σ = 0.1 with I and concentrations in molalities. The extrapolated value of log Ksp o (-10.3) in water is in good agreement with literature data (-10.1 to 10.8) determined in solutions of different composition and ionic strength. The measured values of the activity coefficient, γT(Mn2+) and γ T(CO3 2-), have been used to estimate the stability constant for the formation of the MnCO3 ion pair, K* (MnCO3 0). The value of K0(MnCO3 0) calculated from the values of K* (MnCO3) by the Pitzer equation (σ = 0.1) in this study (4.8 ± 0.1) is in reasonable agreement with literature data.

AB - The solubility of rhodochrosite (MnCO3) at 25°C under constant carbon dioxide partial pressure p(CO2) was determined in NaCl solutions as a function of ionic strength I. The dissolution of MnCO 3(s) for the reaction MnCO3(s) + 2H+ = Mn 2+ + CO2(g) + H2O Kso* = [Mn2+]p(CO2)/[H+]2 has been determined as a function of pH. From these values, we have determined the equilibrium constant for the stoichiometric solubility of MnCO3(s) in NaCl solutions Ksp* = [Mn2+]T[CO 3 2-]T These values have been fitted to the equation log Ksp* = -10.3 + 2.39 I0.5 - 0.69 I with a standard error of σ = 0.1 with I and concentrations in molalities. The extrapolated value of log Ksp o (-10.3) in water is in good agreement with literature data (-10.1 to 10.8) determined in solutions of different composition and ionic strength. The measured values of the activity coefficient, γT(Mn2+) and γ T(CO3 2-), have been used to estimate the stability constant for the formation of the MnCO3 ion pair, K* (MnCO3 0). The value of K0(MnCO3 0) calculated from the values of K* (MnCO3) by the Pitzer equation (σ = 0.1) in this study (4.8 ± 0.1) is in reasonable agreement with literature data.

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