Solubilities of metal carbonates

Abstract

Solubilities in aqueous media of sparingly-soluble metal carbonates play an important role in chemical processes whether they occur in a laboratory, on an industrial scale, or in the geologic environment. Solubility phenomena (i.e. dissolution and precipitation reactions) of metal carbonates control procedures for preparing, separating and purifying chemicals. Moreover, the interactions of the hydrological cycle with the cycle of carbonate rocks, the naturally occurring dissolution of carbonate minerals in water as well as their precipitation on the ocean floor and in the sediments of rivers and lakes can be described by the principles of solubility, although gigantic quantities of material may be involved.The experimental methods for the determination of carbonate solubilities are reviewed and the results are discussed within the frame-work of equilibrium thermodynamics. It will be shown that Gibbs functions of pure stoichiometric carbonate phases can be determined by accurately measuring solubilities in aqueous electrolyte systems. In cases where solid-solid phase transformations and recrystallisations are kinetically inhibited, the methods developed were successfully applied to metastable equilibria. Occasionally, solubility data were even employed to estimate activity coefficients of components forming a series of carbonate solid solutions.Whenever possible the activity coefficients of the reacting species were controlled by use of a constant ionic medium. Solubility constants obtained at various fixed ionic strengths were fitted to the Pitzer equations and extrapolated to infinite dilution. Provided the standard potentials of the respective metal ion/metal electrode are known over a range of ionic strengths the values of solubility constants at infinite dilution can be calculated independently. In any case the optimised thermodynamic constants were incorporated in a comprehensive computer model which permits a wide variety of solubility calculations. These are illustrated by a case study of a multicomponent system with industrial relevance.

IUPAC-NIST Solubility Data Series. 92. Metal Carbonates. Part 1. Solubility and Related Thermodynamic Quantities of Cadmium(II) Carbonate in Aqueous Systems

“…26 and 27), respectively, Three-term Clarke-Glew equation: Kraft,31 assuming that the SIT model is applicable for the whole range of ionic strengths investigated (0 I/mol kg 12 investigated the solubility product of cadmium(II) carbonate painstakingly at low ionic strengths. Although their solubility product is slightly different, the corresponding data fall at least equally close on the curves calculated by themselves 12 and by Gamsjäger et al, 35 respectively. Moreover, the 1993 solubility product of Stipp et al…”

Comprehensive Model of Synthetic Bayer Liquors. Part 1. Overview

“…For instance, database development by geochemical groups 18,[20][21][22][23][24][25] usually involves fitting of solubility products to experimental solubility data as a function of temperature. Among others, Pabalan and Pitzer 4, 19 and one of the present authors 3,9,[26][27][28][29][30][31] have employed a procedure similar to the CALPHAD (CALculation of PHAse Diagrams) method. In this approach, originally developed by Kaufman 32 and others, optimization programs such as the ChemSage optimizer 9 are used to evaluate Gibbs energies of the individual phases as functions of temperature, pressure and composition.…”

High temperature potentiometric carbon dioxide sensor with minimal interference to humidity

“…Other binary systems such as CaCO 3 -Li 2 CO 3 and SrCO 3 -Na 2 CO 3 were also found to show similar stability in the presence of water vapor because CaCO 3 and SrCO 3 have no solubility in water [7,14]. We propose that because of the insolubility of BaCO 3 in water [15], BaCO 3 -coated Li 2 CO 3 exhibits a hydrophobic surface. The infrared data in Fig.…”