Thermodynamic model for solution behavior and solid-liquid equilibrium in Na-Al(III)-Fe(III)-Cr(III)-Cl-H2O system at 25°C

The knowledge of the thermodynamic behavior of multicomponent aqueous electrolyte systems is of main interest in geo-, and environmental-sciences. The main objective of this study is the development of a high accuracy thermodynamic model for solution behavior, and highly soluble M(III)Cl3(s) (M= Al, Fe, Cr) minerals solubility in Na-Al(III)-Cr(III)-Fe(III)-Cl-H2O system at 25°C. Comprehensive thermodynamic models that accurately predict aluminium, chromium and iron aqueous chemistry and M(III) mineral solubilities as a function of pH, solution composition and concentration are critical for understanding many important geochemical and environmental processes involving these metals (e.g., mineral dissolution/alteration, rock formation, changes in rock permeability and fluid flow, soil formation, mass transport, toxic M(III) remediation). Such a model would also have many industrial applications (e.g., aluminium, chromium and iron production, and their corrosion, solve scaling problems in geothermal energy and oil production). Comparisons of solubility and activity calculations with the experimental data in binary and ternary systems indicate that model predictions are within the uncertainty of the data. Limitations of the model due to data insufficiencies are discussed. The solubility modeling approach, implemented to the Pitzer specific interaction equations is employed. The resulting parameterization was developed for the geochemical Pitzer formalism based PHREEQC database.

Activity coefficients of NaCl in NaCl–NaOAc–H2O at 25, 35, and 45 °C

The activity coefficients of NaCl were estimated by measuring the EMFs of the cell[Formula: see text]at four ionic strengths, i.e., 0.5, 1.0, 2.0, and 3.0 mol/kg and at temperatures 25, 35, and 45 °C. The results were analyzed in terms of Harned's rule, the Pitzer and Rush–Johnson–Scatchard treatments. Osmotic coefficients and excess free energies of mixing were calculated at all ionic strengths and temperatures studied. Key words: activity coefficients, sodium chloride, sodium acetate, Pitzer formalism, Scatchard equation.

Thermodynamics of electrolyte solutions: activity coefficients of NaCl in the NaCl–NiCl2–H2O system at 25, 35, and 45 °C

The activity coefficients of NaCl in the NaCl–NiCl2–H2O system were estimated at 25, 35, and 45 °C and total ionic strengths of 0.5, 1.0, 2.0, and 3.0 m by an EMF method using a Na-ion selective electrode and a silver–silver chloride reference electrode. The Harned coefficients were calculated at all the temperatures studied. At 25 °C the data were analysed using the Pitzer formalism. The osmotic coefficients and the excess free energies of mixing were also calculated at 25 °C. Keywords: activity coefficients, sodium chloride, nickel chloride, Pitzer equations, thermodynamics.

Chemistry of Glass Corrosion in High Saline Brines

ABSTRACTExperimental data were obtained for conventional pH values corrected for liquid junction, amorphous silica solubility and glass corrosion in concentrated salt brines. The data were interpreted with a geochemical model. The brine chemistry was described with the Pitzer formalism [1] using a data base which allows calculation of brine compositions in equilibrium with salt minerals at temperatures up to 200°C.In MgCl2 dominated brines Mg silicates form and due to the consumption of Mg the pH decreases with proceeding reaction. A constant pH (about 4) and composition of alteration products is achieved, when the alkali release from the glass balances the Mg consumption. The low pH results in high release of rare earth elements REE and U from the glass. In the NaCl dominated brine MgCl2 becomes exhausted by Mg silicate formation. As long as there is still Mg left in solution the pH decreases. After exhaustion of Mg the pH rises with the alkali release from the glass and analcime is formed.

Densities and apparent molar volumes of aqueous NaCl–KBr mixtures at 298.15 K

Experimental differences in densities Δd of aqueous NaCl–KBr mixtures at I = 1, 2, 3, and 4 mol kg−1 and at 298.15 K are reported from pure NaCl to pure KBr solutions. Mean apparent molar volumes [Formula: see text] are calculated and excess volumes of mixing [Formula: see text] are correlated by Friedman equation, Δd and [Formula: see text] are analysed in terms of recently developed the Pitzer formalism without and with mixing terms. Pitzer equations can estimate the densities of such mixtures with uncommon cations and anions within ±0.02% at the high ionic strength of 4 mol kg−1.