Volumetric Properties of Mixed Electrolyte Aqueous Solutions at Elevated Temperatures and Pressures. The System KCl–NaCl–H₂O to 523.15 K, 40 MPa, and Ionic Strength from (0.1 to 5.8) mol·kg^–1

Abstract

The densities of KCl−NaCl aqueous mixtures were determined at temperatures from (298.15 to 523.15) K, pressures up to 40 MPa, and over a range of compositions at ionic strengths from (0.1 to 5.8) mol•kg −1 . A vibrating-tube densimeter used for the experimental measurements provides the accuracy on density better than 2•10 −4 g•cm −3 . The mean apparent molar volumes of the mixed electrolytes, V mean ϕ , were calculated from the experimental data. At 523.15 K, the change in V mean ϕ from saturated vapor pressure to 40 MPa is comparable to the change with temperature at 10 MPa from ambient conditions to 523.15 K. A Pitzer-type equation was fit to the data set and used to evaluate the individual partial molar volumes of NaCl and KCl in the solutions. The volume of mixing computed from the equation is always positive and displays a nearly symmetrical increase between the NaCl and KCl end-members. It also increases with increasing salt concentration and pressure, and decreases with increasing temperature. The results of this study permit a quantitative modeling of the properties of complex aqueous solutions and simulation of fluid-rock interaction processes occurring in geothermal and hydrothermal systems.

Volumetric Properties of Na2SO4–H2O and Na2SO4–NaCl–H2O Solutions to 523.15 K, 70 MPa

“…The mean apparent molar volume of the ternary electrolyte mixture decreases with temperature and increases with pressure over the range of conditions investigated (Figure ). The pressure-related increase of the mean apparent molar volume of the mixtures is much more significant at high temperatures, and can reach the rate of about 0.25 cm 3 ·mol –1 MPa –1 at T = 523.15 K. These trends of V mean ϕ are similar to the behavior of the mixtures of chlorides. , …”

“…The density difference between an experimental solution and pure water was obtained from the measured period of vibration of the tube filled with water and reference NaCl solutions in the same manner as described in previous studies. , The Hill equation of state for water and the consistent Archer equation for aqueous NaCl solution were used for calibration of the densimeters and calculations. Table contains the results of the measurements and calculated density difference Δρ for experimental solutions in the Na 2 SO 4 –H 2 O and Na 2 SO 4 –NaCl–H 2 O systems.…”

“…The method used in this study is analogous to that described in our previous communications. , The density difference of the Na 2 SO 4 –H 2 O binary solution and the Na 2 SO 4 –NaCl–H 2 O ternary solution with respect to pure water was calculated from the measurements obtained using two vibrating-tube densimeters (a custom-made DMA HP provided by Dr. Hans Stabinger GmbH, and a commercial DMA HP 4100 from Anton Paar). The experimental data were measured at temperatures T of (298.15, 373.15, 423.15, 473.15, and 523.15) K, pressures p up to 70 MPa, and molalities up to 5 mol·kg –1 and 1.2 mol·kg –1 of NaCl and Na 2 SO 4 , respectively.…”

Experimental Data and Modeling of Solution Density and Heat Capacity in the Na–K–Ca–Mg–Cl–H2O System up to 353.15 K and 5 mol·kg–1 Ionic Strength

“…To do this, the various ternary subsystems were studied using experimental data provided by the literature. Saluja et al measured the heat capacity of the Na–Ca–Cl, Na–Mg–Cl, and Ca–Mg–Cl ternary systems between T = (298.15 and 373.15) K. For density, the compilation of Laliberté and the data of Kumar, Zezin et al, , Qiblawey et al, , Deng et al, Yu et al , and Badarayani et al were used. First, the calculations were performed with PhreeSCALE using only the binary interaction parameters.…”

Correlations for Densities of Aqueous Electrolyte Solutions

“…The predicted densities from the refined correlation for the mixed electrolytes show a curved shape at high concentrations–consistent with its quadratic nature. Recently Zezin et al reported extensive new data for the densities of the aqueous NaCl–KCl solution. Their data at 298 K and 0.1 MPa are consistent with the data of Kumar.…”