Determination of Pitzer Parameters for 1‐1 Nitrate and 1‐2 Sulfate Solutions from Freezing Point Data (original) (raw)
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Industrial & Engineering Chemistry Research, 2014
A novel calculation method (see the article in Ind. Eng. Chem. Res. 2014, 53, 5608−5616) was applied in this work to evaluate the ion interaction parameters for the Pitzer model from freezing points of aqueous solutions of pure electrolytes. The freezing-point depression data from aqueous solutions of salts consisting of chloride, bromide, nitrate, chlorate, perchlorate, formate, and acetate ions as anions and lithium, sodium, and potassium ions as cations were used in the present study. The literature data from the research group of Scatchard (
Industrial & Engineering Chemistry Research, 2008
MgCl 2 ) have been measured by a reliable differential temperature technique. The available experimental literature data on the freezing point depression in addition to the vapor pressure data of aqueous electrolyte solutions for NaCl, KCl, KOH, CaCl 2 , MgCl 2 , CaBr 2 , ZnCl 2 and ZnBr 2 have been used to optimize binary interaction parameters between salts and water. The fugacity of water in salt-free aqueous phase has been modeled by the Cubic-Plus-Association (CPA) equation of state. The Debye-Hückel electrostatic term has been used for taking into account the effect of salt on the fugacity of water when electrolytes are present. Model predictions are validated against independent experimental data generated in this work for both single and mixed electrolyte solutions and a good agreement between predictions and experimental data is observed, supporting the reliability of the developed model.
Industrial & Engineering Chemistry Research, 2003
We have predicted the osmotic and activity coefficients of strong electrolyte solutions using a modification of the Pitzer equation. The modified equation can be used for multicomponent aqueous solutions by applying a mixing rule at the Debye-Hü ckel term. We have found that the modification of the Pitzer equation retains the accuracy of the original equation without using any characteristic parameters evaluated from the experimental data. The new equation is predictive and simpler than the original Pitzer equation.
Temperature Dependence of the Parameters in the Pitzer Equations
Journal of Chemical & Engineering Data
The effects of temperature on the virial coefficients in the Pitzer equations are not known in general, and this is because the vast majority of experiments performed to investigate the properties of the aqueous electrolytes were conducted only at a temperature of 25 °C. Consequently, most of the parameters in the Pitzer equations that are available in the literature were estimated at this temperature. Therefore, finding a way to estimate the virial coefficients at different temperatures is highly important. To achieve this, new equations that correlate the virial coefficients with the temperature and the properties of the ions, i.e. ionic radius and ionic charge are derived. As a result, these new derived equations were able to accurately predict the apparent relative molal enthalpies at 25 °C, as well as the activity and osmotic coefficients at temperatures up to 150 °C for electrolytes that are unlikely to form ion pairs. Moreover, comparison plots are presented to demonstrate the good agreement between the predictions of the correlating equations and the experimental data obtained from the literature.
Computers & Geosciences, 2016
The thermal and volumetric properties of complex aqueous solutions are described according to the Pitzer equation, explicitly taking into account the speciation in the aqueous solutions. The thermal properties are the apparent relative molar enthalpy () and the apparent molar heat capacity (,). The volumetric property is the apparent molar volume (). Equations describing these properties are obtained from the temperature or pressure derivatives of the excess Gibbs energy and make it possible to calculate the dilution enthalpy (∆H), the heat capacity () and the density (ρ) of aqueous solutions up to high concentrations. Their implementation in PHREEQC V.3 (Parkhurst and Appelo, 2013) is described and has led to a new numerical tool, called PhreeSCALE. It was tested first, using a set of parameters (specific interaction parameters and standard properties) from the literature for two binary systems (Na 2 SO 4-H 2 O and MgSO 4-H 2 O), for the quaternary K-Na-Cl-SO 4 system (heat capacity only) and for the Na-K-Ca-Mg-Cl-SO 4-HCO 3 system (density only). The results obtained with PhreeSCALE are in agreement with the literature data when the same standard solution heat capacity (C 0) and volume (V 0) values are used. For further applications of this improved computation tool, these standard solution properties were calculated independently, using the Helgeson-Kirkham-Flowers (HKF) equations. By using this kind of approach, most of the Pitzer interaction parameters coming from literature become obsolete since they are not coherent with the standard properties calculated according to the HKF formalism. Consequently a new set of interaction parameters must be determined. This approach was successfully applied to the Na 2 SO 4-H 2 O and MgSO 4-H 2 O binary systems, providing a new set of optimized interaction parameters, consistent with the standard solution properties derived from the HKF equations.
Journal of Electroanalytical Chemistry, 1998
To prove the applicability of the Pitzer equations, modified by us after taking into account the dependence of the solution concentration on the mixing parameters related with the binary solute -solute interactions, we are presenting the analysis of accurate experimental activity coefficient values here determined for the mixed system NaCl + i-alanine +H 2 O up to medium concentrations of both NaCl and the aminoacid. These activity coefficient values were obtained from the emfs of the galvanic cell: Na-glass i-Alanine (m A ), NaCl (m B =I), AgCl Ag. The fitting was done by considering only the binary interaction mixing parameters, i.e. by neglecting the ternary ones (ion-zwitterion -zwitterion and ion -ion -zwitterion). The standard deviation thus found for the fitting ( 90.16 mV, i.e. 90.003 in ln k 9 ) was of the same order as the accepted experimental uncertainty. Activity coefficients for i-alanine in these aqueous solutions, calculated from the use of these modified Pitzer equations, are also presented.
Industrial & Engineering Chemistry Research, 2002
We have correlated simultaneously experimental data for osmotic and activity coefficients of strong electrolyte solutions using the Pitzer equation and a modification of it. The optimal value for the Pitzer b parameter is different from the traditional value of 1.2 when using higher concentrations in its determination. An analysis of the equation shows that it is possible to reduce the model to a three-parameter form that represents the coefficients at molalities as high as 25 with better accuracy than the model as proposed by Pitzer.