Ion Interaction Approach Research Articles

An investigation of the volumetric properties of [formula omitted] -alanine and sodium bromide in water at elevated temperatures and pressures

An optically coupled vibrating tube densimeter has been used to measure the relative densities of aqueous solutions ofl-alanine and sodium bromide in the ranges 397⩽T/K⩽ 521 and 10 ⩽p/MPa⩽ 30. For the solutel-alanine, the reported relative densities have been used to calculate apparent molar volumes which, in turn, have been used in the calculation of partial molar volumes at infinite dilution. The latter data are modeled using an equation of state of the type reported by Helgeson, Kirkham, and Flowers. This model is compared to those recently reported by Clarke and Tremaine. The reported model for the temperature and pressure dependence of the apparent molar volume ofl-alanine in water is used to derive expressions for the apparent molar compressibility and expansibility of this system. Calculated data for the latter property are compared to those available in the literature. In addition, the partial molar volume at infinite dilution for the alanine side chain is calculated by combining the volumetric results reported in this manuscript for aqueousl-alanine solutions with those previously reported for aqueous solutions of glycine. Volumetric results for aqueous sodium bromide solutions have been compared to those calculated from a program by Archer that utilizes the Pitzer Ion Interaction approach.

Volumetric Ion Interaction Parameters for Single-Solute Aqueous Electrolyte Solutions at Various Temperatures

The ion interaction approach developed by Pitzer allows the prediction of thermodynamic characteristics of mixed electrolyte solutions at various temperatures, if the respective parameters for each type of single electrolyte solution are known. Among such thermodynamic characteristics are the volumetric ones (density and apparent molal volumes). A database for the densities and the apparent molal volumes versus concentrations was developed at a temperature interval of 288.15–368.15 K using all available literature sources for each single electrolyte solution formed by various electrically neutral combinations of the following ions (Na+, K+, Mg2+, Ca2+, Sr2+, Ba2+, Cl−, Br−, HCO3−, CO32−, and SO42−). These are the most important ions for industrial solutions as well as for natural waters. Statistical treatment was applied to this database in order to discard poor data. The proper treatment of all sound quality apparent molal volumes, in a wide range of concentrations from infinite dilution through saturation, allowed us to compute sets of volumetric ion interaction parameters (V̄MX0, βMX(0)V, βMX(1)V, βMX(2)V, and CMXV) at various temperatures in a 288.15–368.15 K temperature interval. The validity of the selected sets at various temperatures was demonstrated by a comparison of the experimental and calculated densities for multiple-solute electrolyte solutions containing NaCl, KCl, MgCl2, and CaCl2 with an ionic strength reaching 9.23 that resembled Dead Sea water.

Thermodynamics of the HBr+NiBr2+H2O system from 5°C to 55°C

Abstract The emf of the following cell (A) without liquid junction was used to investigate the HBr+NiBr2+H2O mixed electrolyte system. Pt , H 2 ( g ,1 atm )| HBr (m A ), NiBr 2 (m B )| AgBr , Ag Measurements of the emf were performed for solutions at constant total ionic strengths of 0.05, 0.1, 0.25, 0.5, 1.0, 1.5 and 2.0 mol kg−1 at temperatures ranging from 5°C to 55°C, except for I=2.0 mol kg−1, where measurements were only made at 25°C. The mean activity coefficients of HBr in the mixtures were calculated using the Nernst equation. The thermodynamic properties of unsymmetrical mixtures are interpreted in terms of the simpler Harned's rule, as well as the comprehensive Pitzer's ion-interaction approach including higher order electrostatic effects for electrolyte mixtures. The Harned interaction coefficients αAB and βAB were determined from the data on the HBr+NiBr2 mixture. Literature osmotic coefficient data at 25°C have been used to determine the pure electrolyte Pitzer parameters (β(0), β(1), and Cφ) for NiBr2. The results were combined with the value of ΘH,Ni=0.069 obtained from the HCl+NiCl2+H2O system to determine ΨH,Ni,Br=0.06 from our emf data at 25°C. The effect of temperature (0–55°C) on the Pitzer parameters (β(0), β(1), and Cφ) for HBr and NiBr2 was determined from the present emf measurements, assuming that the higher order electrical terms (ΘH,Ni and ΨH,Ni,Br) were independent of temperature. They were fitted to a simple polynomial function of temperature (°C): β H , Br (0) =0.2085+8.55×10 −4 (t−25)−1.8×10 −4 (t−25) 2 β H , Br (1) =0.3477+18.0×10 −4 (t−25)+3.9×10 −4 (t−25) 2 C H , Br φ =0.001517−7.10×10 −4 (t−25)+1.05×10 −4 (t−25) 2 and β Ni , Br (0) =0.4451−0.0307(t−25)−3.1×10 −4 (t−25) 2 β Ni , Br (1) =1.49+0.0855(t−25)−6.2×10 −4 (t−25) 2 C Ni , Br φ =−0.00626+0.029(t−25)+8.45×10 −4 (t−25) 2 The values of the Pitzer parameters for NiBr2 were of the same order of magnitude as found for other bivalent bromides.

Standardization of pH measurements based on the ion interaction approach

The Pitzer method was used to calculate the pH values on the conventional and “true” scales for the TRIS—TRIS·HCl−NaCl−H2O buffer system in the 0–40 °C temperature region and 0–4 NaCl molality interval. This buffer can be used as a standard for pH measurements in a wide range of ionic strengths. The conventional scale is used in cells without a salt bridge. The “true” scale is recommended for pH measurements using cells with a salt bridge. At the same concentrations of the buffer solution, the “true” scale is essentially transformed into the scale of the National Bureau of Standards (NBS) of the USA.

Predicting Sulfate-Mineral Solubility in Concentrated Waters

Sulfate minerals participate in a variety of mineral-water reactions with waters containing elevated concentrations of dissolved solids. Reliable prediction of sulfate-mineral solubility in concentrated waters is required for a multitude of geological, hydrogeological, industrial, and meteorological applications. Precipitation of pure sulfate minerals or sulfate-bearing solid solutions can limit concentrations of dissolved metals, radionuclides, and other cations at waste-disposal sites, in marine and other naturally occurring saline waters, in industrial waters, and in smog. Formation of these solids can control the major-ion geochemistry of water and, in turn, influence the behavior of trace constituents. One of the most widely used and robust approaches for predicting mineral solubility in concentrated waters is the Pitzer ion-interaction approach as first introduced by Pitzer (1973), as applied to geological systems by Harvie and Weare (1980) and Harvie et al. (1980), and as summarized by Weare (1987). Clegg and Whitfield (1991) and Pitzer (1979a,b; 1991) provided further comprehensive discussions on the developments and application of the ion-interaction approach to predict mineral solubility in natural waters. This chapter focuses on the application of the ion-interaction approach, or its variations, for predicting sulfate-mineral solubility in a variety of geochemical settings. Included are a summary of the Pitzer approach as applied to predictions of mineral solubility, a summary of the available constants for modeling sulfate-mineral solubility, and examples of applications for natural and contaminated sites. The discussion focuses on recent additions to earlier models developed for application to near-Earth-surface temperature and pressure conditions. Applications outside this temperature and pressure range are described only briefly. ### Compositions of concentrated waters The majority of concentrated waters in nature form as a result of solar evaporation of marine and continentally-derived waters. The evaporation of seawater leads to predictable sequences of mineral formation, including precipitation of several common sulfate minerals (e.g. gypsum, …

Thermodynamics of Cm(III) in Concentrated Salt Solutions: Carbonate Complexation in NaCl Solution at 25°C

The carbonate complexation reactions of Cm(III) were studied by time-resolved laser fluorescence spectroscopy in 0–6 m NaCl at 25°C. The ionic strength dependence of the stepwise formation constants for the carbonato complexes Cm(CO3)n3−2n with n = 1, 2, 3, and 4 is described by modeling the activity coefficients of the Cm(III) species with Pitzer's ion-interaction approach. Based on the present results and literature data for Cm(III) and Am (III), the mean carbonate complexation constants at I = 0 are calculated to be: log β101o=8.1 ±0.3, log β102o=13.0 ± 0.6, log β103o=15.2 ± 0.4, and log β 104o=13.0 ± 0.5. Combining these equilibrium constants at infinite dilution and the evaluated set of Pitzer parameters, a model is obtained, that reliably predicts the thermodynamics of bivalent actinide An(III) carbonate complexation in dilute to concentrated NaCl solution.

Ion-Interaction Approach: Pressure Effect on the Solubility of Some Minerals in Submarine Brines and Seawater

The pressure dependence of salt solubility in multiple electrolyte solutions was estimated to 1000 atm. The activity coefficients, thermodynamic solubility products, degrees of saturation, and mineral solubility were calculated with high precision only up to 300 atm because of the absence of compressibility data for mixed electrolyte solutions. The ion-interaction approach developed during the last 2 decades allows the prediction of various thermodynamic properties, including volumetric ones for multiple-solute natural solutions. This approach was applied to the estimation of the depth dependence of solubility for certain evaporite minerals in natural brines. The influence of pressure on solubility products, mean activity coefficients, and degrees of saturation of minerals, such as, halite (NaCl), anhydrite (CaSO4), gypsum (CaSO4·2 H2O), celestite (SrSO4), and barite (BaSO4) were calculated for in situ depths in the Orca Basin (Gulf of Mexico), the Tyro and Bannock II depressions (the Mediterranean Sea), and for average seawater.

Spectroscopic evaluation of thermodynamics of trivalent actinides in brines

A systematic investigation of thermodynamic properties of trivalent aquatic actinides has been initiated in our laboratory to develop models capable of predicting their behavior in natural multicomponent brines of high concentration. An overview on this subject is provided taking curium as a representative for trivalent actinides. Cm(III) is chosen, because of its high fluorescence spectroscopic sensitivity that enables a direct speciation in solution in the nanomolar concentration range. Interactions of Cm(III) with the main natural inorganic ligands Cl −, SO 4 2−, OH − and CO 3 2− are investigated by time resolved laser fluorescence spectroscopy (TRLFS). An overall thermodynamic model for trivalent actinides is developed based on the ion interaction (Pitzer) approach.

Volumetric Properties of Single Aqueous Electrolytes from Zero to Saturation Concentration at 298.15 °K Represented by Pitzer’s Ion-Interaction Equations

The ion interaction approach developed by Pitzer allows the prediction of various thermodynamic characteristics of multiple-solute electrolyte solutions, if the respective parameters for each type of single-solute electrolyte solution are known. The present paper discusses the Pitzer approach to the calculations of the volumetric properties of single-solute electrolyte solutions. The databases for the densities and the apparent molal volumes versus concentrations were created at 298.15 °K using essentially all published relevant data for each single-solute electrolyte solution. Poor experimental data were discarded by a statistical treatment applied to these databases. Proper treatment of all good quality density and apparent molal volume data, in a wide range of concentrations from infinite dilution through saturation, allowed us to evaluate the volumetric ion interaction parameters (V̄0MX, βMX(0)V, βMX(1)V, βMX(2)V, and CMXV) at 298.15 °K for 102 electrolytes. Strong linear relationships between the βMX(1)V, βMX(2)V, or CMXV, and βMX(0)V volumetric ion interaction parameters were observed for all analyzed solutes with slopes depending on the solute valency types.

Ion interaction approach to calculations of volumetric properties of aqueous multiple-solute electrolyte solutions

The ion interaction approach developed by Pitzer was used for the prediction of volumetric properties of mixed electrolyte solutions at 25°C based on parameters calculated from experimental data for single-solute electrolyte solutions. Such an approach was shown to be especially effective for application to the calculation of volumetric properties of natural hypersaline brines and of industrial electrolyte solutions of large complexity. The use of the latest recommended sets of volumetric ion interaction parameters for single electrolyte solutions and symmetrical mixing parameters for Na−K−Cl ion combinations considerably improved the precision of the density calculations of highly concentrated mixed electrolyte solutions and of various natural waters.

Thermodynamic properties of aqueous mixtures of LiCl and Li2SO4 at different temperatures

Emf measurements were made on the cell without liquid junction: Li−ISE LiCl(m1), Li2SO4(m2) Ag/AgCl. The performances of the electrode pairs constructed in our laboratory were tested and exhibited near-Nernstian behavior. The mean activity coefficients of LiCl for the system Li+−Cl−−SO 4 2− −H2O have been investigated by the emf values at temperatures of 0, 15, 35°C and constant total ionic strengths of 0.05, 0.1, 0.5, 1.0, 2.0, 3.0 and 5.0 mol·kg−1. The activity coefficients decrease with increasing temperature and the ionic strength fraction of Li2SO4 in the mixtures. The thermodynamic properties are interpreted by use of Harned's empirical equations and Pitzer's ion interaction approach including the contribution of higher order electrostatic terms. The experimental results obey Harned's rule and are described by using Pitzer equations satisfactorily. The activity coefficients of Li2SO4, the osmotic coefficients and the excess free energies of mixing for the system in the experimental temperature range were reported.

Ion interaction approach for volumetric calculations for solutions of single electrolytes at 25�C

The ion interaction approach of Pitzer permits the prediction of thermodynamic characteristics of multiple-electrolyte solutions if the ion interaction parameters (Pitzer parameters) for each type of single-electrolyte solutions are known. The purpose of the present paper is to suggest the best sets of volumetric Pitzer parameters,\(\bar V_{MX}^O \), β MX (0)V , β MX (1)V , β MX (2)V andC MX V , at 25°C for salts formed from Na+, K+, Mg2+, Ca2+, Cl−, Br−, HCO 3 − , CO 3 2− and SO 4 2− ions. Using essentially all published relevant experimental data, a database for the mass densities and apparent molar volumes at 25°C vs. the solute concentration has been created for each single-electrolyte solution type. Unreliable data were discarded by an appropriate statistical test. The remaining data, covering solute concentrations from infinite dilution to saturation, were used to compute the unrestricted and restricted sets of volumetric Pitzer parameters by least squares. Taking the differences between the calculated and experimental densities and apparent molar volumes as the criterion of quality, the best set of volumetric Pitzer parameters was selected for each type of electrolyte and was used to calculate the mass densities, at 25°C, of some multiple-electrolyte solutions resembling Dead Sea waters.

The solubility of ettringite at 25°C

Available solubility constants indicate that ettringite should be the stable form of calcium aluminate sulfate hydrate with respect to monosulfate in cement porewater. However, monosulfate is generally present in mature cement pastes, usually in the absence of ettringite. The objectives of this study were to determine the solubility product of ettringite under equilibrium conditions and to examine the solubility data used in predictive thermodynamic models. Solubility products were calculated for ettringite prepared from both supersaturated and undersaturated solutions with a pH range between 10.4 and 13.7. The mean solubility product for ettringite dissolution: Ca 6 Al 2 O 6( SO 4) 3 · 32 H 2 O → 6 Ca 2+ + 2 Al( OH) 4 − + 3 SO 4 2− + 4 OH − + 26 H 2 O was 10 −44.91, i.e. Log K sp = -44.91 ± 1.06 (2 S.D.). Activity coefficients were calculated using the specific ion interaction approach. The mean solubility product was close to other values calculated from concentrations reported elsewhere for the solubility of ettringite. As is the case for all solubility products, this value cannot be inserted directly into the databases of other thermodynamic models because of differences in the methods used to calculate activity coefficients and the manner in which ion-pairing is handled by different models. However, raw solubility data are provided for recalculation of the solubility product for use in other models.

Thermodynamics of Ion-Exchange Between Na+/Sr2+ Solutions and the Zeolite Mineral Cinoptilolite

ABSTRACTIon-exchange experiments were conducted at 25 °C between the zeolite mineral clinoptilolite and aqueous solutions of varying equivalent ratios of Na+ and Sr2+ and total concentrations of 0.005, 0.05, and 0.5 N. The experiments were designed to investigate the effects of changes in total solution concentration and in the relative concentrations of exchangeable cations on the following ion-exchange equilibrium:Sr2+ + 2NaZ ⇄ SrZ2 + 2Na+Using the isotherm data at 0.05 N solution concentration, a thermodynamic model for the ion-exchange reaction was derived using a Margules formulation for the activity coefficients of zeolite components and the Pitzer ion-interaction approach for activity coefficients of aqueous ions. The results of the forward experiments showed that the ion-exchange isotherm strongly depends on the total solution concentration. Additional experiments demonstrated that the above ion-exchange reaction is reversible. The derived equilibrium constant, K, and Gibbs energy of ion-exchange, ΔG°, are equal to 0.321±0.021 and 2,820±170 J/mol, respectively.Using thermodynamic parameters derived from the 0.05 N isotherm experiment, the model was used to predict isotherm values at 0.005 and 0.5 N, which showed excellent agreement with measured data. Because the thermodynamic model used in this study can be easily extended to ternary and more complicated mixtures, it may be useful for modeling ion-exchange equilibria in multicomponent geochemical systems.

The solubility of barite and celestite in sodium sulfate: Evaluation of thermodynamic data

The solubilities of barite [BaSO4(c)] and celestite [SrSO4(c)] in Na2SO4 were studied and found to be significantly lower than the experimental values reported in the literature. Our new solubility data are in excellent agreement with the predictions of ion interaction models, which have previously been parameterized primarily from solubility data obtained in chloride media. Our solubility data were analyzed both in terms of aqueous thermodynamic models that included ion association species and in terms of ion interaction models that did not require the explicit recognition of such species. In the case of SrSO4, although both ion association and ion interaction models can accurately model our solubility data, the ion interaction approach is preferred because it is easier to extend to higher concentrations. In the case of BaSO4, the aqueous ion interactions appear to be stronger than those for SrSO4, and so the explicit recognition of a BaSO4(aq) ion association species is preferred. The logarithms of the thermodynamic solubility products (log K sp ) for celestite and barite were −6.62±0.02 and −10.05±0.05, respectively. When the data were analyzed using models that include ion association species, the logarithms of the thermodynamic equilibrium constants for the SrSO4(aq) and BaSO4(aq) association reactions were 1.86±0.03 and 2.72±0.09, respectively.

Thermodynamics of Aqueous Electrolyte Solutions with Liquid‐Liquid Phase Separation

AbstractInitiated by the recent observation of liquid‐liquid phase separation in aqueous solutions of tetra‐n‐butylammonium thiocyanate, a treatment of the thermodynamic properties of aqueous electrolyte solutions in relation to liquid‐liquid phase equilibria is given. For analyzing the thermodynamic data, the ion interaction approach of Pitzer is used in which the osmotic coefficient is described by a long‐range term for Coulombic interaction plus a virial coefficient series to account for short‐range specific interactions. It is shown that the ion‐interaction approach is flexible enough to incorporate liquid‐liquid phase equilibria in a natural and simple way. For 1:1 electrolytes liquid‐liquid coexistence curves are predicted if the second virial coefficients entering into Pitzer's theory are large and negative and the third (or higher) virial coefficients are positive. Experimental data show that largely negative second virial coefficients are generally present if large cations are combined with large anions, so that coexistence curves are predicted for aqueous solutions of tetraalkylammonium salts with large anions. Many of these salts are practically insoluble at room temperature, but at higher temperatures, where crystallization does not interfere, these predictions are experimentally confirmed for tetrabutylammonium iodide, tetrapropylammonium perchlorate and tetrapropylammonium picrate. For 2:2 electrolytes phase separation can result from the behaviour of the long‐range contribution to the osmotic coefficient alone, even if the virial coefficients are positive. Thermodynamic data for aqueous MgSO4 solutions at elevated temperatures indicate a coexistence curve with a lower consolute point at about 239°C, submerged by the crystallization curve. The same approach predicts a coexistence curve for aqueous UO2SO4 solutions, in qualitative agreement with the observation of a lower critical point at 286°C. In earlier interpretations this coexistence curve has been attributed to the peculiar properties of the uranyl ion, but it would appear that to a first approximation the miscibility gap in aqueous UO2SO4 at elevated temperatures represents a general property of 2:2 electrolytes, which for UO2SO4 becomes visible due to the high solubility of this salt.

Apparent molar heat capacity and other thermodynamic properties of aqueous potassium chloride solutions to high temperatures and pressures

Heat capacities of KCl solutions have been measured from 413 to 573 K at 200 bar over the molality range of 0.05-3.0 mol kg/sup -1/. These were combined with literature data on volumes, heat capacities, enthalpies, and osmotic coefficients up to a temperature of 599 K and a pressure of 500 bar to yield comprehensive equations for the calculation of the thermodynamic properties of KCl(aq) to high temperatures and pressures by using ion-interaction approach of Pitzer.

The geochemistry of Ca, Sr, Ba and Ra sulfates in some deep brines from the Palo Duro Basin, Texas

The geochemistry of Ca, Sr, Ba and Ra sulfates in some deep brines from the Palo Duro Basin of north Texas, was studied to define geochemical controls on radionuclides such as 90Sr and 226Ra. Published solubility data for gypsum, anhydrite, celestite, barite and RaSO 4 were first reevaluated, in most cases using the ion interaction approach of Pitzer, to determine solubility products of the sulfates as a function of temperature and pressure. Ionic strengths of the brines were from 2.9 to 4.8 m, their temperatures and pressures up to 40°C and 130 bars. Saturation indices of the sulfates were computed with the ion-interaction approach in one brine from the arkosic granite wash fades and four from the carbonate Wolfcamp Formation. All five brines are saturated with respect to gypsum, anhydrite and celestite, and three of the five with respect to barite. All are undersaturated by from 5 to 6 orders of magnitude with respect to pure RaSO 4. 226Ra concentrations in the brines, which ranged from 10 −11.3 to 10 −12.7 m, are not controlled by RaSO 4 solubility or adsorption, but possibly by the solubility of trace Ra solid solutions in sulfates including celestite and barite.

The Thermodynamics and Geochemistry of Ca, Sr, Ba, and Ra Sulfates in Some Deep Brines From the Palo Duro Basin, Texas

AbstractThe work reported here involved application of the ion-interaction approach of Pitzer [1] [2] to model the activities of some major and minor cations and major anions in deep brine systems at elevated temperatures and pressures.The solubilities of anhydrite (CaS04), gypsum (CaSO4·2H2O), celestite (SrS04), barite (BaS04), and radium sulfate (RaSO4) in brines from the Wolfcamp Formation and granite wash facies, Palo Duro Basin, Texas, were modeled using ion-interaction equations. Waters with ionic strengths ranging from 2.89 to 4.76 m, and temperatures and pressures up to 40°C and 130 bars were sampled from five horizons in three wells, at depths between 970 and 1,670 meters. Theoretical solubility products as a function of temperature and pressure were obtained for comparison with ion activity products computed using ion-interaction theory. The effect of temperature on model calculations was found to reside almost entirely in the Debye-Hückel AΦ parameter, which accordingly was corrected for brine temperatures [3].Modeling results indicated that all five brines are saturated with respect to anhydrite and celestite, and three of the five with respect to barite. Saturation may result from hydrologic connection with adjacent overlying evaporite units, or increased Ca, Sr and Ba concentrations caused by their desorption from clays. Radium concentrations, which range from 10-11.3 to 10-12.7 m, are not controlled by RaSO4 solubility or adsorption, but probably by solid solution in other sulfate minerals in these low pH (4.4 – 6.3) high calcium (0.18 – 0.52 m) brines [4] [5].