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1.
The water activities of the mixed aqueous electrolyte NaCl–BaCl 2(aq) are measured at total molalities from 0.25 mol kg −1 to about saturation for different ionic strength fractions ( y) of NaCl with y=0.33,0.50,0.67. The results allow the deduction of osmotic coefficients. The experimental results are compared with the predictions of the Zdanovskii, Stokes, and Robinson (ZSR), Kusik and Meissner (KM), Robinson and Stokes (RS), Lietzke and Stoughton (LSII), Reilly, Wood, and Robinson (RWR), and Pitzer models. From these measurements, the Pitzer mixing ionic parameters are determined and used to predict the solute activity coefficients in the mixture. The excess Gibbs energy is also determined. 相似文献
2.
In order to develop the nitrate deposits found close to Lop Nur in the Xinjiang region in China, the solubilities of the system Na +,Mg 2+/Cl −,SO 42−, NO 3−–H 2O and its subsystems, the quaternary systems Na +,Mg 2+/SO 42−,NO 3−–H 2O and Mg 2+/Cl −,SO 42−,NO 3−–H 2O, were studied at 298.15 K. The phase diagrams were plotted according to the solubilities achieved. In the equilibrium phase diagram of Mg 2+/Cl −,SO 42−,NO 3−–H 2O, there are two invariant points, five univariant curves and four regions of crystallization: Mg(NO 3) 26H 2O,MgCl 26H 2O,MgSO 47H 2O and MgSO 4(1–6)H 2O. In the equilibrium phase diagram of Na +,Mg 2+/SO 42−, NO 3−–H 2O, there are five invariant points, eleven univariant curves and seven regions of crystallization: Na 2SO 4,Na 2SO 410H 2O,NaNO 3,MgSO 4Na 2SO 44H 2O,NaNO 3Na 2SO 42H 2O,Mg(NO 3) 26H 2O and MgSO 47H 2O. In the equilibrium phase diagram of the Na +, Mg 2+/Cl −,SO 42−,NO 3−–H 2O system, there are six invariant points, and ten regions of crystallization: NaCl, NaNO 3,Na 2SO 4,Na 2SO 410H 2O,MgSO 4Na 2SO 44H 2O, NaNO 3Na 2SO 42H 2O,MgCl 26H 2O,Mg(NO 3) 26H 2O, MgSO 4(1–6)H 2O and MgSO 47H 2O. 相似文献
3.
The Pitzerion-interaction model has been used for thermodynamic simulation of the ternary solutions KCl-K 2Cr 2O 7-H 2O, KBr-K 2Cr 2O 7-H 2O and K 2SO 4-K 2Cr 2O 7-H 2O and the quaternary system KCl-K 2SO 4-K 2Cr 2O 7-H 2O at T=298.15 K. The necessary thermodynamic functions (binary and ternary parameters of interionic interaction and thermodynamic solubility products) have been calculated and the theoretical solubility isotherms have been plotted. Good agreement between experimentally determined and calculated solubilities has been found. 相似文献
5.
Solubility isotherms of the ternary system (NH 4Cl+CaCl 2+H 2O) were elaborately determined at T= (273.15 and 298.15) K by using the isothermal method. In the equilibrium phase diagram, there are two solubility branches corresponding to the solid phases CaCl 2⋅6H 2O and NH 4Cl. Invariant point compositions are 36.32 wt% CaCl 2 and 3.4 wt% NH 4Cl at 273.15 K, and 45.86 wt% CaCl 2 and 5.22 wt% NH 4Cl at 298.15 K. A Pitzer-Simonson-Clegg thermodynamic model was applied to represent the thermodynamic properties of this ternary system and to construct a partial phase diagram of the ternary system at temperatures between (273.15 and 323.15) K. It was found in the predicted solubility phase diagram that the double salt 2NH 4Cl⋅CaCl 2⋅3H 2O, found by other authors at (323.1 and 348.1) K, will disappear at temperatures below 298.15 K. Besides, it was found that there are two peritectic points in the ternary system with peritectic temperatures at 299.65 K and 298.15 K, and the former peritectic point falls just on the line between the composition points of NH 4Cl and CaCl 2⋅6H 2O. According to phase rule, a solution made of this point will begin to crystallize at 299.65 K and end at 298 K and therefore can be acted as a “pseudo eutectic” phase change material (PCM). A heat storing and releasing experiment of 50 grams of the PCM was carried out, obtaining a satisfying result. 相似文献
6.
The component solubilities in NaCl–RbCl–H 2O, KCl–CsCl–H 2O and KBr–CsBr–H 2O systems at 25 C were calculated by using the Pitzer ion interaction model and its extended HW models. Excellent agreement with experimental solubilities indicated that the models can be successfully used to calculate the component solubilities. This study affords the necessary parameters for solubility predictions of complicated systems containing rubidium and caesium and establishes a theoretical basis for the separation of these valuable metals from salt lake brine. 相似文献
7.
A new equation of state (EOS) and the corresponding computer program package VLEWM are developed to calculate vapor–liquid phase equilibria and volumetric properties of CH 4–H 2O system at low temperatures. The EOS can predict vapor–liquid equilibria and volumetric properties of CH 4–H 2O system accurately at temperatures 273–383 K, and at pressures 0–1000 bar. The program package VLEWM is written in FORTRAN 77. It provides two main functions: (1) to calculate the composition in vapor phase and liquid phase of CH 4–H 2O system at equilibrium and (2) to judge the phase and to calculate molar volume of CH 4–H 2O mixture. 相似文献
9.
The component solubilities of the HCl–MgCl 2–H 2O system at 40 °C were calculated by using Pitzer’s ion-interaction model and the solubility equilibrium constant of HCl⋅MgCl 2⋅7H 2O at 40 °C was evaluated according to the solubility data for the HCl–MgCl 2–H 2O system at −19.8, 0, 20, 25 and 50 °C. This study can provide the parameters necessary for solubility prediction for the HCl–LiCl–MgCl 2–H 2O system at 40 °C and supply a theoretical basis for the manufacturing process which was proposed by Gao and employed to extract MgCl 2⋅6H 2O from salt lake brine. 相似文献
10.
Phase relations in the ZrO 2–LaO 1.5 system were studied experimentally in the temperature range from 1673 to 1973 K. X-ray diffraction and scanning electron microscopy were employed to obtain the structural information and the compositions of the tetragonal and pyrochlore (La 2Zr 2O 7) phases. The solubility of LaO 1.5 in the tetragonal phase was determined to be very small. The homogeneity range of the pyrochlore phase is estimated to be less than 2 mol% at 1973 K, and less than 1 mol% at 1673 K according to the present work. Based on the experimental results obtained in this work, as well as the available phase diagram and thermodynamic data in literature, a self-consistent thermodynamic assessment was carried out by using the ionic sublattice solution model. 相似文献
11.
The Pitzer interaction model, which has been applied successfully to the thermodynamic simulation of electrolyte solutions and electrolyte–nonelectrolyte solutions, was extended to nonelectrolyte–nonelectrolyte solution system. In the present work, the modified Pitzer model was used for calculation and correlation of the ternary CO(NH 2) 2–H 2O 2–H 2O system at 283.15 K. The value of the Pitzer interaction parameters for the ternary system and the thermodynamic solubility product of CO(NH 2) 2⋅H 2O 2 were determined using a least-square optimization procedure with coupling activity coefficient and solubility data. The predicted isothermal solubilities agree well with the result obtained from the experiment. The results indicated that the modified Pitzer model could be successfully used to predict the component solubility of the nonelectrolyte–nonelectrolyte system. 相似文献
12.
Vapor–liquid equilibrium data for the poly(vinylpyrrolidone) (PV P)+NaH 2PO 4+H 2O system have been determined experimentally using the improved isopiestic method at 298.15, 308.15 and 318.15 K. The effect of temperature on the vapor–liquid equilibrium has been studied and compared with that on the liquid–liquid equilibrium of the aqueous PV P+NaH 2PO 4 two-phase system. It was found that the slope of constant water activity lines and tie-lines increased with increasing the temperature. The results have been discussed on the basis of the effect of temperature on the hydrophobicity of the polymer. Furthermore, the segment-based local composition Wilson model has been used for the correlation of the experimental water activity data. The agreement between the correlation and the experimental data is good. 相似文献
13.
Hygrometric measurements of the water activity are reported for the thermodynamic properties of the mixed aqueous electrolyte systems of ammonium–calcium chloride and ammonium–barium chloride at 298.15 K. The measurements were made at a large number of total molalities, varying from 0.4 mol kg −1 to saturation at three ionic-strength fractions (y ) of NH 4Cl for the systems NH 4Cl–CaCl 2 (aq) and NH 4Cl–BaCl 2 (aq) with y=0.20,0.50 and 0.80. The experimental data are reported as water activities and osmotic coefficients at various molalities, along with derived values of the activity coefficients of both solutes. The ranges of water activities aw are 0.800–0.989 for ammonium–barium chlorides and aw=0.560–0.989 for ammonium–calcium chlorides. The activity coefficients were calculated by means of a thermodynamic model based on a variant of the Pitzer ion-interaction equations with extended binary parameters. However, the results were also compared for the precision of the presentation of the osmotic coefficients using an extended model with the calculations of the Zdanovskii–Stokes–Robinson, Kusik and Meissner, Robinson and Stokes, Lietzke and Stoughton, Reilly, Wood and Robinson, and Pitzer models. 相似文献
14.
The solidification behaviour of the CaO–SiO 2–Al 2O 3–CaF 2–10% MgO system, which is similar to the inclusion compositions in the stainless steel and the crystallization of spinel have been investigated using XRD, SEM-EDS, and an image analyser. The solidification mode and the phase equilibria were computed by employing thermochemical software. The liquidus temperature of the oxides containing 5% CaF 2 increases with increasing alumina content from 10% to 30%, while the solidus temperature has little dependence on alumina content. The size of spinel crystals in the final microstructure increases on increasing the content of alumina, resulting from that the oxides spending more time at higher temperatures below the liquidus temperature, where crystal growth is generally faster than nucleation, during slow cooling. The liquidus temperature of the oxides containing 30% Al 2O 3 is scarcely varied, while the solidus temperature decreases by increasing the content of CaF 2 to 10%. The size of spinel crystals decreases as the content of CaF 2 increases, resulting from the fact that the oxides could spend more time at relatively lower temperatures, where nucleation is faster than growth, during the cooling process. 相似文献
15.
The nanocomposite TiO 2/molecular sieve 4A as photocatalyst was fabricated and employed to develop an effective, rapid, simple and environmental friendly method for chemical oxygen demand (COD) detection. This new approach overcomes the problems with direct use of TiO 2 for COD detection techniques such as photo-decay and difficulties in recycling. Here, the COD value was calculated from the changed absorbance of Cr(VI) and the mechanism of the photocatalytic oxidation was discussed. Under the optimal condition, the COD sensor gave a detection limit of 0.24 mg l −1 and a linear range from 3.0 to 15 mg l −1. With the recoveries from 97 to 103% and without any pretreatments for complicated samples, the developed sensor was successfully applied to the determination of COD in real samples. 相似文献
16.
In order to maintain consistency, analytical expressions for the free energy of mixing of phases should reproduce not only the phase diagrams but also the experimentally determined activities. Information on the partial molar free energies and the phase boundaries, in turn, can be used to estimate the free energy of formation of compounds. An examination of thermochemical data in the CaO-SiO2 system showed that ΔGδf values for -Ca2Si04, which are stable at temperatures above 1710°K, are limited a maximum of 1800°K. The free energy of formation in a temperature range from about 1700 to 2400°K was estimated from the phase boundary and the activity of silica to be as follows: 2Ca0(s) + Si02(cristo.) = Ca2Si04() ΔG°f = −86303.50 − 34.338 Tjoules An analytical expression for the free energy of mixing of the liquid phase was obtained for the entire composition range in the CaO-Si02 system. Confidence in the estimated G‡f for -Ca2Si04 was demonstrated by good agreement of the calculated phase diagram and the experimentally determined activity of silica. 相似文献
17.
Available phase diagram and thermodynamic data on the eighteen binary systems containing Li + , Na +, K +, S0 4=, CO 3=, and OH − have been collected and critically assessed. A set of self-consistent thermodynamic parameters describing the free energies of the compounds, solid solutions, and liquid solutions in the binary systems has been formulated. The phase diagrams have been calculated, and estimated error limits of all diagrams are given. 相似文献
18.
The influence of the SnO 2 surface modification by the SnO 2–Au nanocomposites on conductivity response to such reducing gases as CO and H 2 has been analyzed in the present paper. Both initial SnO 2 films, subjected for surface modification, and SnO 2–Au nanocomposites were deposited by Successive Ionic Layer Deposition (SILD) method. The SnO 2–Au nanocomposites with Au/Sn ratio 1 were synthesized using HAuCl 4 and SnCl 2 precursors. The thickness of the Au-SnO 2 nanolayers varied from 0.7–1.0 nm to 10–15 nm. It was established that the increase in the thickness of the SnO 2–Au nanocomposite layer formed on the surface of the SnO 2 films was accompanied by both the improvement of sensor response and the decrease in response and recovery times. An explanation of the observed effects has been proposed. 相似文献
19.
Interpenetrating polymer networks (IPN) hydrogels composed of poly(vinyl acohol) (PVA) and poly(acrylic acid-co-2-acrylamido-2-methyl propyl sulfonic acid) (P(AA/AMPS)) were synthesized by solution polymerization. The IPN hydrogels were characterized using Fourier-transform infrared (FT-IR) and X-ray diffraction (XRD). The results indicated that strong hydrogen bond was formed between PVA and P(AA/AMPS), and the crystallinity of PVA in IPN hydrogels was declined significantly. The swelling/deswelling properties of IPN hydrogel in aqueous Na 2SO 4 solution were studied. When a sheet of water swollen IPN hydrogel (all the samples were swollen in deionized water) was placed in aqueous Na 2SO 4 solution, the IPN hydrogel shrunk. However, if a voltage was applied, the IPN hydrogel shrunk at high concentration of Na 2SO 4 solution, but swelled at low concentration. The results show that the critical concentration of Na 2SO 4 solution is about 0.005 mol/L. The stimuli response of the IPN hydrogel in electric field was also investigated. When water swollen samples were placed between a pair of electrodes in aqueous Na 2SO 4 solution, the IPN hydrogel showed significant bending behavior upon the application of an electric field. The bending direction of the IPN hydrogel depends on the concentration of Na 2SO 4 solution. At high concentration the IPN hydrogel bended toward anode, contrarily, at low concentration the IPN hydrogel bended toward cathode. The critical concentration of Na 2SO 4 solution is also about 0.005 mol/L. Further investigation showed that the gel component, concentration of aqueous Na 2SO 4 solution and the applied voltage influenced the bending speed of IPN hydrogel. 相似文献
20.
Phase equilibria and thermodynamic properties of the KCl–K 2CO 3–NaCl–Na 2CO 3 system were analyzed on the basis of the thermodynamic evaluation of the KCl–NaCl,KCl–K 2CO 3,NaCl–Na 2CO 3,K 2CO 3–Na 2CO 3 and KCl–K 2CO 3–NaCl–Na 2CO 3 systems. The Gibbs energies of individual phases was approximated by two-sublattice models for ionic liquids and crystals. Most of the experimental information was well described by the present set of thermodynamic parameters. The lowest monovariant eutectic temperature in the KCl–NaCl–Na 2CO 3 system is located at 573 °C, with a composition of XNa2CO3=0.31, XKCl=0.35 and XNaCl=0.34. 相似文献
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