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1.
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2.
A semi-empirical model for gas solubilities in high temperature brines was developed by modification of the Pitzer interaction model (Pitzer, 1973) and evaluated by least-squares fitting to available P-T-X data for carbon dioxide, hydrogen sulfide, and methane in pure water and in aqueous sodium chloride solutions. Over the range of experimental data used (25°–350°C, NaCl concentration 0–6 m, PCO2 1–150 atm. PCH4 1–30 atm, PCH4 1–1700 atm), standard deviations of fit in the natural logarithm of the Henry's law ratio were 0.096 for CO2, 0.093 for H2S and 0.116 for CH4.The model has several advantages. First, it has a theoretical basis which can easily be extended for the inclusion of more than one salt or gas. Second, the equations simplify to the empirically derived equation of Setschenow, in the limit of infinite dilution. Finally, the model is easily integrated into a framework of equations which can yield all of the thermodynamic properties of the system.An example in which values of the model parameters for interaction of gas with salt may be used to estimate the effect of dissolved gas or salt solubility is given.  相似文献   

3.
This article presents methods for predicting the standard partial molar Gibbs energy (standard chemical potential) and related derivative properties of aqueous hydroxy and aminoderivatives of (alkyl)benzenes over a wide range of temperatures and pressures. A thorough literature overview was conducted for collecting all available experimental data resulting from phase equilibrium, calorimetric and volumetric measurements that allow calculation of the thermodynamic properties of hydration. New experimental values are presented for solubility in water of isomeric toluidines and for the partial molal volume of phenol and cresols at high temperatures. Building upon the acquired database several prediction schemes were developed and tested for calculating the standard thermodynamic properties (and namely the Gibbs energy of hydration) of aqueous alkylphenols and alkylanilines as a function of temperature and pressure. First, a simple group contribution method was proposed for estimations at 298.15 K and 0.1 MPa using the simultaneous treatment of all available data on hydration properties at near ambient conditions. Second, this group contribution method allowed re-adjustment of the parameters of the Helgeson-Kirkham-Flowers model (HKF) using a new procedure proposed recently by Plyasunov and Shock [Plyasunov, A.V., Shock, E.L., 2001b. Correlation strategy for determining the parameters of the revised Helgeson-Kirkham-Flowers model for aqueous nonelectrolytes. Geochim. Cosmochim. Acta65, 3879-3900]. Third, using the Sedlbauer-O’Connell-Wood equation of state for aqueous species (SOCW), group contributions were determined for predictions at high temperatures and pressures by simultaneous correlation of all available thermodynamic data on hydration properties. The latter method was constrained by the group contributions at 298.15 K and 0.1 MPa making both group contribution schemes consistent at near ambient conditions. The calculations from the HKF and SOCW equations of state and those from the simple thermodynamic integration of the data at 298.15 K and 0.1 MPa were compared for several alkylphenols and alkylanilines. Equilibrium constants for hydration reactions obtained from the three approaches are in very good agreement at temperatures to at least 400 K. At higher temperatures we assess the accuracy of different predictive schemes and their associated uncertainties. The reliable predictions of the standard chemical potentials to at least 573 K and 100 MPa are possible by the group contribution method using the SOCW equation of state.  相似文献   

4.
The standard thermodynamic properties and Helgeson-Kirkham-Flowers (HKF) parameters for Sb(OH)3(aq) have been estimated. For this purpose, the available solubility data for senarmontite, valentinite, stibnite, and native Sb in a wide range of temperatures (15 to 450°C) and pressures (1 to 1000 bar), and thermodynamic properties of Sb oxides (senarmontite and valentinite) have been critically analyzed. Published data were complimented by results from new experiments performed by solubility and solid-state galvanic cell methods. Both experimental data and thermodynamic calculations show that the hydroxide complex Sb(OH)3(aq) is primarily responsible for hydrothermal transport of antimony, especially at temperatures above 250°C.  相似文献   

5.
The solubility of chlorargyrite, AgClcr, was experimentally studied in NaCl solutions (0.1, 0.2, and 0.5 m) as a function of the concentration of boric acid (up to 5 m) at 70–300°C and saturated water vapor pressure. The experimental data indicated the existence of the chloroborate species B(OH)3Cl−. The published data on the thermodynamic properties of aqueous complexes in the B-Na-Cl-O-H system were analyzed. The obtained HKF parameters of aqueous species can be used to calculate equilibria in the system up to 350°C. Original Russian Text ? N.N. Akinfiev, M.V. Voronin, A.V. Zotov, V.Yu. Prokof’ev, 2006, published in Geokhimiya, 2006, No. 9, pp. 937–949.  相似文献   

6.
New experimental data on the solubility of NaCl in gaseous CO2 were obtained at pressures (P) of 30–70 MPa and temperatures of 623 and 673 K on experimental equipment making possible to sample a portion of the gas in the course of the experiment. The new measures have demonstrated that the NaCl solubility increases with increasing temperature (T) and pressure and is approximately four to five orders of magnitude higher than the saturated vapor pressure of NaCl at the corresponding temperature. The paper also reports newly obtained experimental data on the equilibrium conditions of the reaction of talc decomposition into enstatite and quartz at a variable H2O/NaCl ratio in the fluid. The results of the experiments validate the empirical equations previously suggested for H2O and NaCl activities in concentrated aqueous salt solutions that can be used in describing silica-saturated fluids at high T-P parameters. A new empirical equation is suggested for the Gibbs free mixing energy in the H2O-CO2-NaCl ternary system, with the parameters of the equation calibrated against experimental data on phase equilibria in marginal binary systems and on the location of the boundary of the region of homogeneous three-component fluid according to data on synthetic fluid inclusions in quartz.  相似文献   

7.
Ivanov  M. V.  Bushmin  S. A.  Aranovich  L. Y. 《Doklady Earth Sciences》2018,481(2):1086-1090
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8.
The paper presents critical analysis of literature data on the stability constants of aqueous species in the system Zn-O-H-S?II-Cl. In order to more accurately determine the composition and stability of chloride Zn complexes, additional experiments were carried out to determine the solubility of sphalerite ZnSc in chloride-sulfide solutions at 175°C and the saturated vapor pressure of the solution. Having processed the data, we obtained the thermodynamic properties at 25°C and parameters of the HKF (Helgeson-Kirkham-Flowers) equation of state (EoS) for hydroxide, chloride and hydrosulfide Zn complexes. The constants of sphalerite dissolution reactions with the formation of hydrosulfide and, particularly, chloride complexes increase with increasing temperature. The predominant Zn transport species in high-temperatures (>250°C) chloride-sulfide hydrothermal solutions are chloride complexes, first of all, ZnCl 4 2? . As the temperature decreases, the concentrations of complexes with smaller numbers of Cl? ligands increase. The region of weakly acidic to alkaline pH is dominated by hydrosulfide Zn complexes, but their concentrations in equilibrium with sphalerite are relatively low (a few ppm at 400°C and S concentrations <0.1 mol kg?1) and decreases with a temperature decrease. In the region dominated by chloride complexes, the concentration of dissolved Zn can amount to a few fractions of a percent at near-neutral pH, 400°C, and m(NaCl) = 1.0 and increases if the fluid becomes more acidic. An extremely important factor controlling the concentrations of dissolved Zn is temperature: cooling leads to the effective precipitation of sphalerite, particularly in the region dominated by chloride complexes. The thermodynamic properties of the solid phases and parameters of the HKF model for aqueous species in the system Zn-O-H-S-II-Cl are presented in the on-line version of the FreeGC database (http://www-b.ga.gov.au/minerals/research/methodology/geofluids/thermo/calculator/search.jsp), which enables calculating the Gibbs energy values of components of the system and reaction constants involving these components at PT parameters up to 600°C and 3 kbar.  相似文献   

9.
The thermodynamic behaviour of fluids can be accurately described by equations of state (EoS) in terms of the Helmholtz energy, with temperature and density as independent variables. The known properties in dynamic simulations of power or refrigeration cycles are usually different from temperature and density. Partial derivatives of state properties with respect to the known properties of the simulation have to be transformed into partial derivatives with respect to the independent variables of the EoS. This transformation is demonstrated step by step for the single-phase region, along the saturation line and within the two-phase region.  相似文献   

10.
The thermodynamic properties of 154 mineral end-members, 13 silicate liquid end-members and 22 aqueous fluid species are presented in a revised and updated data set. The use of a temperature-dependent thermal expansion and bulk modulus, and the use of high-pressure equations of state for solids and fluids, allows calculation of mineral–fluid equilibria to 100  kbar pressure or higher. A pressure-dependent Landau model for order–disorder permits extension of disordering transitions to high pressures, and, in particular, allows the alpha–beta quartz transition to be handled more satisfactorily. Several melt end-members have been included to enable calculation of simple phase equilibria and as a first stage in developing melt mixing models in NCKFMASH. The simple aqueous species density model has been extended to enable speciation calculations and mineral solubility determination involving minerals and aqueous species at high temperatures and pressures. The data set has also been improved by incorporation of many new phase equilibrium constraints, calorimetric studies and new measurements of molar volume, thermal expansion and compressibility. This has led to a significant improvement in the level of agreement with the available experimental phase equilibria, and to greater flexibility in calculation of complex mineral equilibria. It is also shown that there is very good agreement between the data set and the most recent available calorimetric data.  相似文献   

11.
The hydraulic conductivity, Ks, is one of the most important hydraulic properties which controls the water and solute movement into the soil. It is measured on soil specimens in the laboratory. On the other hand, sometimes it is obtained by tests carried out in the field by a number of researchers. Therefore, several experimental formulas have developed to predict it. Recently, soft computing tools have been used to evaluate the hydraulic conductivity. However, these tools are not as transparent as empirical formulas. In this study, another soft computing approach, i.e. model trees, have been used for predicting the hydraulic conductivity. The main advantage of model trees is that, unlike the other data learning tools, they are easier to use and represent understandable mathematical rules more clearly. In this paper, a new formula that includes some parameters is derived to estimate the hydraulic conductivity. To develop the new formulas, experimental data sets of hydraulic conductivity were used. A comparison is made between the estimated hydraulic conductivity by this new formula and formulas given by other’s researches.  相似文献   

12.
 General equations to correlate and predict the thermodynamic properties of hydrated borates were developed based on the experimental results according to their structural types. The thermodynamic properties (ΔH f 0 and ΔG f 0) of a hydrated borate phase are the sum of the contributions of the cations in aqueous solution, the borate polyanions, and the structural water to the corresponding thermodynamic properties. This method is called the group contribution method, and it is extensively used to calculate the thermodynamic properties of many kinds of inorganic compounds, such as silicates and clay minerals. Received: 23 November 1998 / Accepted: 11 October 1999  相似文献   

13.
刘斌  徐金明 《岩石学报》2007,23(1):105-112
During the microthermometric measurement(cooling)of aqueous inclusions with multivolatile components,solid crystals of gas clathrates often occur with snow-flower-or soft-ice appearances.The structural formula of these solids is M·nH_2O(where n≥5.67).Many hydrocarbons,related compounds and their binary or multi-component mixtures may generate gas clathrates.This phenomenum is of fundamental importance to the study of inclusions with hydrocarbon aqueous solutions,because this is related to the determination of inclusion parameters and the computation of thermodynamic parameters. In the nature most aqueous inclusions contain not merely one volatile component but multi-volatile components.Therefore,the measurement of aqueous inclusions with multivolatile components is of universal significance and great importance.There have been many studies and available formula or figures about the computation of thermodynamic parameters for aqueous inclusions with one volatile component.Nevertheless,there are few studies concerning with muhivolatile components and it is very difficult to computate thermodynamic parameters for aqueous inclusions with these components. In this paper,hydrated coefficient K is introduced.K_i is the ratio of molar fraction of component i in the gas phase to that in the gas clathrate,or K_i=y_i/x_i.Because K is a function of temperatures and pressures,it can be used to evaluate the temperature-pressure conditions on the phase behavior with muhivolatile components. Based on the regression analysis of available experimental data,the authors have developed computational expression of hydrated coefficients in relation to temperature and pressure for most hydrocarbons and other volatile components,which is helpful to conveniently compute thermodynamic parameters on stability state for elathrates with volatile components.As aqueous inclusions with muhivolatile components are common in the nature,by the use of final melting temperatures of clathrates from mierothermometry and these formula,fluid density of gas phase with valotile components and bulk fluid density of inclusions can be accurately calculated. Furthermore,this method may provide foundations to determine the isochores of inclusions and to calculate trapping temperatures and pressures. Finally,detailed analyses for two computational examples about aqueous inclusions with muhivolatile components are presented.  相似文献   

14.
Molecular based equations of state (EOS) are attractive because they can take into account the energetic contribution of the main types of molecular interactions. This study models vapor-liquid equilibrium (VLE) and PVTx properties of the H2O-CO2 binary system using a Lennard-Jones (LJ) referenced SAFT (Statistical Associating Fluid Theory) EOS. The improved SAFT-LJ EOS is defined in terms of the residual molar Helmholtz energy, which is a sum of four terms representing the contributions from LJ segment-segment interactions, chain-forming among the LJ segments, short-range associations and long-range multi-polar interactions. CO2 is modeled as a linear chain molecule with a constant quadrupole moment, and H2O is modeled as a spherical molecule with four association sites and a dipole moment. The multi-polar contribution to Helmholtz energy, including the dipole-dipole, dipole-quadrupole, and quadrupole-quadrupole contribution for H2O-CO2 system, is calculated using the theory of Gubbins and Twu (1978). Six parameters for pure H2O and four parameters for pure CO2 are needed in our model. The Van der Waals one-fluid mixing rule is used to calculate the Lennard-Jones energy parameter and volume parameter for the mixture. Two or three binary parameters are needed for CO2-H2O mixtures, which are evaluated from phase equilibrium data of the binary system. Comparison with the experimental data shows that our model represents the PVT properties of CO2 better than other SAFT EOS without a quadrupole contribution. For the CO2-H2O system, our model agrees well with the vapor-liquid equilibrium data from 323-623 K. The average relative deviation for CO2 solubility (expressed in mole fraction) in water is within 6%. Our model can also predict the PVTx properties of CO2-H2O mixtures up to 1073 K and 3000 bar. The good performance of this model indicates that: (1) taking account of the multi-polar contribution explicitly improves the agreement of calculated properties with experimental data at high temperatures and high pressures, (2) the molecular-based EOS with just a few parameters fit to data in the sub-critical region can predict the thermodynamic properties of fluids over a wide range of P-T conditions.  相似文献   

15.
The aim of the present work was to study the thermodynamic equilibria between water and a homo-ionic montmorillonite SWy-1 saturated by different cations. The choice of this smectite is justified by the large set of experimental data available from the literature for eight different interlayer cations: Na+, K+, Rb+, Cs+, Mg2+, Ca2+, Sr2+, and Ba2+. In particular, studies by [Cases et al., 1992], [Cases et al., 1997] and [Bérend et al., 1995] are providing heat of adsorption data, pairs of desorption-adsorption isotherms, and information about the partition of adsorption-desorption water molecules between external surfaces and internal spaces. By calculating the effective amount of hydration water as the difference between the so-called gravimetric water and the surface covering water, a thermodynamic model was then developed, based on the concept of Ransom and Helgeson (1994) considering an asymmetric subregular binary solid solution between a fully hydrated and a anhydrous smectite. A set of six thermodynamic parameters ( and four Margules parameters) was extracted by a least square method from measurements of enthalpies of adsorption and paired adsorption-desorption isotherms for each interlayer cation. These six initial parameters were then used to determine a complete set of standard thermodynamic hydration parameters (, heat capacity, molar volume, and number of interlayer H2O) and quantify, for each cation, the number of moles of hydration water molecules as a function of relative humidity and temperature. The validation of the standard state thermodynamic properties of hydration for each end member was carried out using three approaches: (1) a comparison with experimental isotherms obtained on hetero-ionic and homo-ionic SWy-1 smectite at different temperatures; (2) a comparison with the experimental integral enthalpy and entropy of hydration of the SWy-1 smectite; and (3) a comparison with experimental isotherms acquired on various smectites (Upton, MX80, Arizona) with different layer charges.Eventually, the present work demonstrates that, from a limited number of measurements, it is possible to provide the hydration thermodynamic parameters for hydrated smectites with different compositions and under different conditions of temperature and relative humidity, using the newly developed predictive model.  相似文献   

16.
We propose a thermodynamic model for the mixing of gases in aqueous sodium chloride solutions valid to high pressures, high temperatures, and high ionic strength solutions. Our model couples Henry's Law with any equation of state to reproduce experimental data in the aqueous-rich liquid and gas-rich vapor region. In our model, the chemical potential of the solute in the brine is related to the chemical potential of the solute in pure water through salting-out coefficients. The model reproduces all crucial phenomena of binary (gas–water) and pseudo-binary (gas–water–salt) vapor–liquid mixtures below their critical point. We applied the model to reproduce the phase behavior of nitrogen in water and NaCl brines. Results and discussions are shown.  相似文献   

17.
In the present research, the removal of lead(II) and copper(II) from aqueous solutions is studied, using SnO2 nanowires as new adsorbent on solid-phase extraction disk and compared with pine core and buttonwood as biosorbents. Batch adsorption experiments were performed as a function of pH, adsorption time, solute concentration and adsorbent dose for biosorbents. Also, the pH, transfer rate of solution and metal concentration were selected as experimental parameters for the removal of heavy metals by SnO2 nanowires. All of the parameters were optimized by experimental design method for sorbents. The experimental equilibrium adsorption data are tested for the Langmuir and Freundlich equations. Results indicate the following order to fit the isotherms: Langmuir > Freundlich, in case of lead and copper ions. The removal of Cu(II) and Pb(II) was performed by selected sorbents in the presence of interferences ions. This led to no remarkable decrease in the removal efficiency of SnO2 nanowires. Using the SnO2 nanowires in the wastewater treatment indicated 96.8 and 85.28% removal efficiency in only 7 min for Pb(II) and Cu(II), respectively. SnO2 nanowires were found as reusable sorbent. Therefore, SnO2 nanowires have a good potential for application in environmental protection.  相似文献   

18.
We find clear intrinsic anharmonicity in the NaCl-B1 phase by examining the equation of state (EoS) based on previous ultrasonic velocity data for pressures up to 0.8 GPa and temperatures up to 800 K. The experimental EoS for this phase shows that its specific heat at constant volume (C V ) is significantly smaller than that based on a harmonic model. Also, the sign of $\left( {{{\partial C_{V} } \mathord{\left/ {\vphantom {{\partial C_{V} } {\partial P}}} \right. \kern-0pt} {\partial P}}} \right)_{T} ,$ which is normally negative in the quasi-harmonic approximation, is unexpectedly positive. The thermodynamic Grüneisen parameter (γ), which has frequently been assumed to be a single-variable function of molar volume, shows not only volume dependence but also negative temperature dependence. To understand these features of C V and γ, we introduce a thermodynamic model including positive quartic anharmonicity. To make an anharmonic model advancing the ordinarily quasi-harmonic approximation model, we introduce two parameters: anharmonic characteristic temperature (θ a ) and its volume derivative. In the anharmonic model, the value of C V is calculated along an isochore using classical statistical mechanics and a harmonic quantum correction. At high temperatures, the decrease in C V from the Dulong-Petit limit is related to the value of T/θ a . For infinitely large θ a , the system is approximately quasi-harmonic. The temperature dependence of γ is related to C V by the thermodynamic identity $\left( {{{\partial C_{V} } \mathord{\left/ {\vphantom {{\partial C_{V} } {\partial \ln V}}} \right. \kern-0pt} {\partial \ln V}}} \right)_{T} = C_{V} \left( {{{\partial \gamma } \mathord{\left/ {\vphantom {{\partial \gamma } {\partial \ln T}}} \right. \kern-0pt} {\partial \ln T}}} \right)_{V} + \gamma \left( {{{\partial C_{V} } \mathord{\left/ {\vphantom {{\partial C_{V} } {\partial \ln T}}} \right. \kern-0pt} {\partial \ln T}}} \right)_{V}.$ Even though our modification of the quasi-harmonic approximation is simple, our anharmonic model succeeds in reproducing the experimental γ and C V simultaneously for the NaCl-B1 phase.  相似文献   

19.
Presented is an improved model for the prediction of phase equilibria and cage occupancy of CH4 and CO2 hydrate in aqueous systems. Different from most hydrate models that employ Kihara potential or Lennard-Jones potential with parameters derived from experimental phase equilibrium data of hydrates, we use atomic site-site potentials to account for the angle-dependent molecular interactions with parameters directly from ab initio calculation results. Because of this treatment, our model can predict the phase equilibria of CH4 hydrate and CO2 hydrate in binary systems over a wide temperature-pressure range (from 243-318 K, and from 10-3000 bar for CH4 hydrate; from 253-293 K, and from 5-2000 bar for CO2 hydrate) with accuracy close to experiment. The average deviation of this model from experimental data is less than 3% in pressures for a given temperature. This accuracy is similar to previous models for pressures below 500 bar, but is more accurate than previous models at higher pressures. This model is also capable of predicting the cage occupancy and hydration number for CH4 hydrate and CO2 hydrate without fitting any experimental data. The success of this study validates the predictability of ab initio intermolecular potentials for thermodynamic properties.  相似文献   

20.
Available experimental data on the solubility of Nb2O5 and the stability constants for particles of an aqueous solution in the Nb–O–H–F system were processed. As a result, a set of thermodynamic properties for 25°C and 1 bar was obtained, in addition to the equation parameters for the HKF model (Helgeson–Kirkham–Flowers) for hydroxo and hydroxofluoride niobium complexes. F– ion is the most important factor governing the concentration of dissolved Nb: neutral hydroxo complex Nb(OH)5(aq) is formed at a low HF concentration, whereas an increase in HF results in an increase in the first Nb(OH)4F(aq) and second Nb(OH)3F2(aq) fluoride complexes. The Nb(OH)5F– oxofluoride anion determines oxide solubility in alkali F-bearing fluids. Neutralization of acidic fluoride solution can be the main factor leading to niobium deposition.  相似文献   

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