Wet Residue Method Research Articles

Phase Equilibrium and Crystallization Process of the Ternary System KCl-(NH2)2CO-H2O at Different Temperatures

The phase equilibriums of the ternary system KCl-(NH2)2CO-H2O at 303.15 K, 323.15 K, 333.15 K, and 343.15 K were studied using the isothermal dissolution equilibrium method, in which the composition of equilibrium solid phase was determined by Schreinemaker’s wet residue method and X-ray diffraction (XRD) method. It was found that the ternary system is a simple cosaturated system, without the formation of neither double salt nor solid solution. Wilson and NRTL models were employed to correlate in the solubility data of the system at experimental temperatures. The maximum values of RAD and RMSD of the Wilson model were 2.18 × 10−2 and 0.83 and those of the NRTL model were 1.69 × 10−2 and 0.40, respectively. The two models were utilized to forecast solubility data at various temperatures, and the obtained outcomes were in line with the literature data. Based on the experimental solubility data at 343.15 K, the cooling crystallization process of the system was monitored online by focused beam reflectance measurement (FBRM) and particle video microscope (PVM). The crystal products were characterized by XRD, scanning electron microscope (SEM), and energy dispersive spectrometry (EDS). The results showed that the precipitation of (NH2)2CO occurred during the crystallization process, and this was followed by KCl. KCl was formed on the surface of (NH2)2CO crystal. The crystal was a simple mixture containing KCl and (NH2)2CO.

Phase equilibria in the ternary systems LiCl–LiBr–H2O and LiCl–LiBr–CH3OH at 298 K

Oil gas field brine is a dominant liquid mineral resource in Sichuan Basin, and its rational development and utilization is of great significance to the national economy. In order to explore the physicochemical properties of brine and provide theoretical guidance for the comprehensive utilization of brine, the isothermal solubilities of the ternary systems LiCl − LiBr − H2O and LiCl − LiBr − CH3OH at 298 K were determined by employing the isothermal dissolution equilibrium method. Based on the measured composition of the liquid phase, wet solid phase and equilibrium solid phase, isothermal phase diagrams of the two systems at 298 K were drawn. The results show that according to the phase diagram of the ternary system LiCl − LiBr − H2O at 298 K, there is no single salt and double salt formation, but the crystalline region precipitated by the solid solution occupies all the crystalline space. The phase region is divided by a solubility boundary line into two parts, namely the liquid phase unsaturated region located below the isotherm and the completely mutually soluble solid solution crystallization region above it. Therefore, the two single salts LiCl and LiBr could not be successfully separated with the guidance of this phase diagram. The ternary system LiCl − LiBr − CH3OH at 298 K has single salt and solid solution formed, but no double salt determined. The phase diagram of the ternary system LiCl − LiBr − CH3OH consists of an invariant point, two isothermal solubility lines, and two crystallization regions precipitated with Li(Cl, Br) and LiCl, respectively. Using the phase diagram as a guiding tool for phase separation, LiCl can be acquired by crystallization and filtration operations, but it cannot be achieved for LiBr. In this work, a combination of wet residue method and XRD is used to identify the equilibrium solid phase. Selecting the particle swarm optimization algorithm, the solubility predictions of the ternary systems LiCl − LiBr − H2O and LiCl − LiBr − CH3OH at 298 K were achieved through the well-established Pitzer model. The solubility simulation results satisfactorily matched with the experimental values, indicating that the parameters selected for the simulation have strong applicability.

Measurement and correlation of solid–liquid equilibrium of ternary system KCl-CO(NH2)2-H2O at 313.15 K and 353.15 K

In the paper, the phase equilibrium of the ternary system KCl-CO(NH2)2-H2O was studied through the isothermal solution equilibrium method at 313.15 K and 353.15 K under atmospheric pressure. The equilibrium solid phase was identified through Schreinemaker's wet residue method and X-ray diffraction. Two isothermal phase equilibrium diagrams of the system were constructed based on the measured solubility and composition of wet residue. The phase diagrams show that the system is a simple eutectic system. Each phase diagram includes one invariant point, two univariate isotherm dissolution curves and three crystallization regions. Two thermodynamic models (Wilson and NRTL) were applied to correlate the measured solubility values. The maximum values of the relative average deviation (RAD) and root-mean-square deviation (RMSD) were 5.61 % and 1.20 % with Wilson model, 2.86 % and 0.63 % with NRTL model, respectively, which demonstrated that the two models had good correlation with the ternary system at the experimental conditions.

Phase behaviour of the ternary systems Rb2SO4(1)-RbBr(2)-H2O(3)/Cs2SO4(1)-CsBr(2)-H2O(3) at T = 288.15, 298.15, 308.15 K

The phase equilibrium and physic-chemical properties of Rb2SO4(1)-RbBr(2)-H2O(3)/Cs2SO4(1)-CsBr(2)-H2O(3) systems at T = (288.15, 298.15 and 308.15) K were determined by the isothermal solution saturation method. At the three temperatures, the two systems both contain one invariant point, two univariant curves, and three crystallization regions. The Schreinemaker’s wet residue method and X-ray powder diffraction method were used to verify the solid phase. The phase diagrams of Rb2SO4(1)-RbBr(2)-H2O(3) and Cs2SO4(1)-CsBr(2)-H2O(3) at the three temperatures show that higher temperature reduces the area of the crystallization region of the salts (RbBr and CsBr). The comparison of the two systems at 298.15 K suggests that the crystallization region area of the salts is strongly affected by the solubility and hydration ability of the salts. The refractive index of these systems reached the maximum at the invariant point. At different temperatures, the refractive index increases with increasing temperatures. The results in this paper may provide useful information for the separation of the salts from aqueous solution.

Solid-Liquid Phase Equilibria in the Quinary System NaCl + NaOH + Na2CO3 + Na2SO4 + H2O at 363.15 K.

Solid–liquid equilibria in the quinary system NaCl + NaOH + Na2CO3 + Na2SO4 + H2O at 363.15 K were measured by the wet residue method, and the equilibrium solid phases and solubilities of saturated solutions were determined experimentally. Using the experimental results, dry-salt phase diagrams and water diagrams versus composition diagrams were plotted (saturated with saturated sodium chloride, sodium hydroxide, sodium carbonate, and sodium sulfate). The experimental results show that there are a solid solution (γ-salt, mNa2SO4·nNa2CO3) and co-saturation complex salts (S3, Na2SO4·NaCl·NaOH and S1, NaOH·Na2SO4) formed in this quinary system. Based on Xu’s activity coefficient model, the solubilities of the quinary system NaCl + NaOH + Na2CO3 + Na2SO4 + H2O at 363.15 K were calculated with corresponding parameters. Comparing the experimental and calculated results, it was shown that the calculated values had a good agreement with the experimental ones.

Determination and Calculation of Phase Equilibrium for Aqueous Ternary System (NH2)2CO+KCl+H2O at 283.15K

The solid-liquid phase equilibrium for ternary system (NH2)2CO+KCl+H2O was determined by isothermal saturation method at 283.15K under atmosphere pressure. The isothermal phase diagrams was drawn in according to the measured solubility data. There are one co-saturated point and two pure solids occurred in this ternary system. The solid phases were confirmed by Schreinemaker’s wet residue method and X-ray powder diffraction. Two thermodynamic models, Wilson model and NRTL model, were used to calculate the solubility data. The value of root mean-square deviation in Wilson model and NRTL model for this ternary system was 0.22 and 0.66 respectively, and the value of relative average deviation was 0.61% and 2.33% respectively, which indicated that the calculated data and the experimental results are nearly consistent.

Solid-liquid phase equilibria of quaternary systems Na+//Cl−, CO32−, SO42− - H2O and Na+//Cl−, CO32−, NO3− - H2O at T = 313.15 K

The solid-liquid equilibrium of quaternary systems (Na+//Cl−, CO32−, NO3− -H2O) and (Na+//Cl−, CO32−, SO42− -H2O) at 313.15 K was studied by an isothermal solution saturation method and the solubility of salts and equilibrium solid phases in the two systems was determined. The solid phases formed in the systems studied were determined by the Schreinemaker wet residue method. Based on the measured data, dry-salt phase diagrams and the relevant water-phase diagrams were plotted in the two systems. The stable phase diagram of Na+//Cl−, CO32−, NO3− -H2O at 313.15 K is characterized by one quaternary invariant point (Q), three univariant curves, and three crystallographic forms (corresponding to NaCl, NaNO3 and Na2CO3·H2O). The crystallization region of NaNO3 (I) is the smallest, and its solubility is the greatest, which indicates that NaNO3 has a strong salt-out effect on Na2CO3·H2O and NaCl. The composition of the solution at equilibrium corresponding to invariant point is w(NaCl) = 9.76 wt%, w(NaNO3) = 32.79 wt%, w(Na2CO3) = 6.10 wt%. Therefore, it can be considered that there is no double salt and solid solution in the quaternary system, which belongs to the simple quaternary system. For the quaternary systems (Na+//Cl−, CO32−, SO42− -H2O) at 313.15 K, experimental results indicate that there are four crystallographic forms (NaCl, Na2CO3·H2O, Na2SO4 and Bur (2Na2SO4 Na2CO3)), five univariant curves, and two invariant points corresponding to three salts, that is (NaCl + Na2SO4 + 2Na2SO4 Na2CO3) and (NaCl + Na2CO3·H2O + 2Na2SO4 Na2CO3), respectively. The experimental results show that this system is a complex eutectic type, and no solid solutions are found at the investigated temperature. All the physical properties (ρ, η, nD) of the equilibrium two quaternary systems change regularly with concentration change of the liquid phase. The phase equilibria in the quinary Na+//C1−, SO42−, CO32−, NO3−-H2O system at 313.15 K were also studied using the through and intermediate translation techniques together. All data and results obtained in this paper are of great significance to the design and optimization of the fractional crystallization process of the high-saline wastewater in coal chemical industry.

Solid-liquid stable phase equilibria of the quaternary system Na+ //Cl−, SO42−, CO32−-H2O and its subsystems Na+ //Cl−, CO32−-H2O and Na+ //SO42−, CO32−-H2O at 353.15 K

The solid-liquid phase equilibria of the solution in the quaternary system Na+ //Cl−, SO42−, CO32−-H2O and its subsystems Na+ //Cl−, CO32−-H2O and Na+ //SO42−, CO32−-H2O at 353.15 K were measured by isothermal solution saturation method. The equilibrium solids were determined by the Schreinemaker's method of wet residues and X-ray diffraction (XRD). Based on the experimental data, the phase diagrams were plotted and analysed. There is one monohydrate in the ternary system Na+ //CO32−, Cl−-H2O at T = 353.15 K, and the phase diagram contains one invariant point, two univariant curves and four crystallization regions. The ternary system Na+ //SO42−, CO32−−H2O at T = 353.15 K is more complex than the previous system since one monohydrate and one anhydrous double salt are found; the phase diagram contains two invariant points, three univariant curves and six crystallization regions. The phase diagram of the quaternary system Na+ //Cl−, SO42−, CO32−-H2O at 353.15 K includes two invariant points, five univariant curves, and four crystallization fields of single salts corresponding to NaCl, Na2SO4, Na2CO2·H2O and 2Na2SO4·Na2CO2. The results obtained in this study can help identify the solutions from which fractional crystallization of Na2SO4 and NaCl will be more effective.

Solid–Liquid Phase Equilibrium for Ternary Systems of p-Nitroacetophenone plus m-Nitroacetophenone plus Methanol/Toluene/Ethyl Acetate

The mutual solubilities for ternary systems of p-nitroacetophenone (1) + m-nitroacetophenone (2) + methanol (3), p-nitroacetophenone (1) + m-nitroacetophenone (2) + toluene (3), and p-nitroacetophenone (1) + m-nitroacetophenone (2) + ethyl acetate (3) were investigated through a steady method at 283.15, 298.15, and 313.15 K, respectively, under a local ambient pressure of 101.2 kPa. The isothermal phase diagrams of the three systems were constructed in terms of the obtained mutual solubilities. At a fixed temperature, there were two neat solids formed, namely neat p-nitroacetophenone and neat m-nitroacetophenone, which were recognized through Schreinemakers’ wet residue method. The crystallization regions of neat p-nitroacetophenone and neat m-nitroacetophenone increased with decreasing temperature. The mutual solubility was correlated through the Wilson and NRTL equations. The relative average deviations for p-nitroacetophenone + m-nitroacetophenone + methanol/toluene/ethyl acetate systems were, respectively, 4.44 × 10–2, 3.86 × 10–2, and 3.35 × 10–2 for the NRTL equation and 4.33 × 10–2, 2.51 × 10–2, and 2.29 × 10–2 for the Wilson equation. The acquired solubility data and the ternary phase diagrams for the three systems were very significant for designing and optimizing the purification process of p-nitroacetophenone and m-nitroacetophenone mixtures.

Phase equilibria in Mg(NO3)2–Ln(NO3)3 (Ln = Nd, Sm, Eu, Tb)–HNO3 (∼20%)–H2O systems at 298.15 K and thermodynamic properties of Mg3Ln2(NO3)12·24H2O (Ln = Nd, Sm)

The phase diagrams of the Mg(NO3)2–Ln(NO3)3 (Ln = Nd, Sm, Eu, Tb)–HNO3–H2O systems in the (∼20%) HNO3 regions at T = 298.15 K were determined by using an isothermal solution saturation method. The Schreinemaker’s wet residues method was used to determine the compositions of solid-phases. Both Mg(NO3)2–Nd(NO3)3–HNO3–H2O and Mg(NO3)2–Sm(NO3)3–HNO3–H2O systems are complicated with three equilibrium solid phases Mg(NO3)2·6H2O, Mg3Ln2(NO3)12·24H2O and Ln(NO3)3·6H2O (Ln = Nd, Sm). But the systems Mg(NO3)2–Eu(NO3)3–HNO3–H2O and Mg(NO3)2–Tb(NO3)3Tb–HNO3–H2O are simple eutonic type. The two new solid-phase compounds Mg3Nd2(NO3)12·24H2O and Mg3Sm2(NO3)12·24H2O are congruently soluble in an average medium of ∼20 mass % HNO3, and they were identified and characterized by the methods of powder X-ray diffraction, X–ray diffraction single crystal structure analysis, and thermogravimetric/differential thermogravimetric. The XRD diffraction patterns for the two new solid-phase compounds are identical due to their isomorphic structure. They belong to hexagonal systems, with space group R3. For Mg3Nd2(NO3)12·24H2O, a = b = (1.0993 ± 0.0005) nm, c = (1.7211 ± 0.0007) nm, V = (1.8012 ± 0.0013) nm3, Dc = (4.2532 ± 0.0024) g·cm−3, Z = 3; for Mg3Sm2(NO3)12·24H2O, (a = b = 1.1198 ± 0.0004) nm, c = (1.7257 ± 0.0006) nm, V = (1.8742 ± 0.0011) nm3, Dc = (4.1201 ± 0.0012) g cm−3, Z = 3. The standard molar enthalpies of solution of the compounds Mg3Nd2(NO3)12·24H2O and Mg3Sm2(NO3)12·24H2O in water (aq) were measured to be (101.26 ± 0.77) kJ mol−1 and (80.27 ± 0.81) kJ mol−1, and their standard molar enthalpies of formation were calculated to be – (12214.13 ± 2.5) kJ mol−1 and – (12183.6 ± 2.5) kJ mol−1, respectively.

Solid-liquid equilibrium for the ternary systems (Na2CO3 + NaCl + H2O) and (Na2CO3 + Na2SO4 + H2O) at 313.15 K and atmospheric pressure

The stable (solid + liquid) phase equilibrium and physico-chemical properties of the ternary systems (Na2CO3 + NaCl + H2O) and (Na2CO3 + Na2SO4 + H2O) at T = 313.15 K have determined by the method of isothermal solution saturation. The solid phases formed in the systems studied were determined by the Schreinemaker wet residue method. According to the experimental data, the phase diagrams and the diagrams of physico-chemical properties versus composition were plotted. It was found that there is one invariant point, two univariant curves and three fields of crystallization in the ternary systems (Na2CO3 + NaCl + H2O) at T = 313.15 K. The three crystallization regions correspond to NaCl (I), Na2CO3·H2O (II), the mixed of (NaCl + Na2CO3·H2O) (III). Field EFUC (IV) corresponds to unsaturated solution. Based on the phase diagrams obtained, we analyzed each invariant point. When Na2CO3 and NaCl were analyzed as (15.80, 17.04) wt%, respectively, the ternary system (Na2CO3 + NaCl + H2O) reached saturation at T = 313.15 K. The phase diagram of the ternary system at 313.15 K includes two invariant points, three invariant curves, and three fields of crystallization of single salts corresponding to Na2CO3, Na2CO3·2Na2SO4, Na2SO4. The two invariant points are cosaturated with two salts, that is (Na2CO3·H2O + Na2CO3·2Na2SO4) and (Na2SO4 + Na2CO3·2Na2SO4), respectively. In the phase diagram of the two ternary systems at 313.15 K, the crystallization region of Na2SO4 was significantly larger than the crystallization region of Na2CO3·H2O and NaCl. The quaternary phase equilibrium in Na+//C1−, CO32−, SO42−-H2O system at 313.15 K was also researched by means the through and intermediate translation techniques together. Thus, knowledge of (solid + liquid) equilibrium, especially the crystalline fields at T = 313.15 K, would be extremely valuable to design and optimize solvent extraction process of Na2SO4 and other crystallization processes involving the two ternary systems in the industrial production.

The Phase and Physicochemical Properties Diagrams of Systems Rb+(Mg2+)//Cl– and Borate–H2O at 323 K

The phase and physicochemical properties diagrams at 323 K of systems Rb+//Cl–, borate–H2O, and Mg2+//Cl–, borate–H2O were plotted using the solubilities, densities, and refractive indices of the systems. The Schreinemakers’ wet residue method and the X-ray diffraction method were used for the determination of the compositions of solid phase. Results show that these two systems belong to the hydrate I type, without solid solution or double salt formation. The phase diagrams of both systems consist of one invariant point, two monovariant curves, and two crystallization zones. The borates formed in the studied systems are RbB5O6(OH)4 · 2H2O, and MgB4O5(OH)4 · 7H2O. The comparison between the stable phase diagrams of the system Rb+//Cl–, borate–H2O at 323 and 348 K shows that no matter at which temperature point, the crystallization form of salts are not changed and the crystallization zones have slightly changed.

The Stable Phase Equilibria of the Ternary Systems Na2SO4 + Rb2SO4 (Cs2SO4) + H2O at 298.2 K

To understand the crystallographic forms of salts in sulfate systems containing sodium and rubidium (cesium), the stable phase equilibria of ternary systems Na2SO4 + Rb2SO4 + H2O and Na2SO4 + Cs2SO4 + H2O at 298.2 K were studied with the isothermal dissolution method. The composition and crystallographic forms of the equilibrated solid phase was verified by Schreinemaker’s wet residue method combined with X-ray diffraction. Experimental results show that there is no double salt or solid solution formed. The stable phase diagram of Na2SO4 + Rb2SO4 + H2O at 298.2 K is characterized by one invariant point (H), two univariant curves, and two crystallographic forms (corresponding to Na2SO4·10H2O and Rb2SO4). The ternary system Na2SO4 + Cs2SO4 + H2O is of the hydrate type II, there are two invariant points (E1, E2), three univariant curves, and three crystallographic forms (corresponding to salts Na2SO4·10H2O, Na2SO4 and Cs2SO4). Affected by the unique structure of Cs+, both salt Na2SO4·10H2O and Na2SO4 have be...

Ternary phase diagram of phenanthrene and carbazole in different solvents and its application in the separation of them

The separation of phenanthrene (PHE) and carbazole (CAR) has been a tough job since the formation of solid solutions. Development of new separation strategy for PHE-CAR mixture highly depends on their phase equilibrium behaviour. In this work, ternary phase diagrams of phenanthrene (PHE) and carbazole (CAR) in dimethylformamide (DMF), acetone, acetonitrile (MeCN) and toluene at T = 308.15 K under normal atmosphere were determined through wet residue method. It was found that PHE-rich solid solution α was formed in the particular composition range of PHE-end. On the contrary, no CAR-rich solid solution was formed in CAR-end. These results were further verified through powder X-ray diffraction (PXRD) and differential scanning calorimetry (DSC). Based on the ternary phase diagrams, a difference coefficient of solubility (Ds) was put forward to assist screening and evaluation of solvents for solution crystallization. Among the four tested solvents, toluene is the most suitable one for separating PHE-CAR mixture.

Determination and Modeling of Solid–Liquid Equilibrium for Ternary Systems of Terephthaldialdehyde + 4-Hydroxybenzaldehyde + Ethyl Acetate/Acetone

The stable solid–liquid phase equilibrium for ternary systems of terephthaldialdehyde + 4-hydroxybenzaldehyde + ethyl acetate and terephthaldialdehyde + 4-hydroxybenzaldehyde + acetone was determined using the isothermal saturation method at 293.15, 303.15, and 313.15 K under ambient pressure of 101.2 kPa. In terms of the obtained mutual solubility data, the isothermal phase diagrams of the two systems were constructed. At a given temperature, there were two pure solids formed, pure 4-hydroxybenzaldehyde and pure terephthaldialdehyde, which were identified by Schreinemakers’ wet residue method and X-ray powder diffraction analysis. The crystallization zones of pure 4-hydroxybenzaldehyde and pure terephthaldialdehyde increased with rising temperature. The crystalline zone of terephthaldialdehyde was larger than that of 4-hydroxybenzaldehyde at the same temperature. The mutual solubility data of solid–liquid phase equilibrium were correlated with nonrandom two-liquid (NRTL) and Wilson models. The calculated...

Phase Equilibria in the Aqueous Ternary Systems (NaCl + NaBO2 + H2O) and (Na2SO4 + NaBO2 + H2O) at 298.15 K and 0.1 MPa

With the isothermal dissolution equilibrium method and wet-residue method, the solubility data as well as physicochemical properties including density, refractive index, and pH value of the two ternary systems (NaCl + NaBO2 + H2O) and (Na2SO4 + NaBO2 + H2O) at 298.15 K and 0.1 MPa have been experimentally determined, and the relatively phase diagrams have been established for the first time. In the ternary system (NaCl + NaBO2 + H2O), two invariant points, three univariant curves, and three crystallization regions corresponding to sodium chloride (NaCl), sodium metaborate tetrahydrate (NaBO2·4H2O), and a congruent double salt teepleite (NaCl·NaBO2·2H2O) were detected. While in the ternary system (Na2SO4 + NaBO2 + H2O), there are one invariant point, two univariant curves, and two crystallization regions corresponding to NaBO2·4H2O and mirabilite (Na2SO4·10H2O). The physicochemical properties (density, refractive index, and pH value) in the two systems present a regular variation versus that with the chang...

Solid-liquid Equilibria in the Ternary Systems (NaCl+SrCl2+H2O) and (KCl+SrCl2+H2O) at 288.15 K and 0.1 MPa

Solid-liquid phase equilibria of the two ternary systems (NaCl+SrCl2+H2O) and (KCl+SrCl2+H2O) at T=288.15 K and p=0.1 MPa were studied using the isothermal dissolution equilibrium method. Solubilities of the equilibrium liquid phase were determined, and the solids were also investigated by the Schreinemaker method of wet residues. In the ternary system (NaCl+SrCl2+H2O) at 288.15 K, there is one invariant point corresponding to (NaCl+SrCl2·6H2O) and two crystallization regions corresponding to NaCl and SrCl2·6H2O. The crystallized area of SrCl2·6H2O decreased with the increasing temperature, while that of NaCl increased slightly. In the ternary system (KCl+SrCl2+H2O) at 288.15 K, there is one invariant point(KCl+SrCl2·6H2O) and two crystallization regions cor-responding to KCl and SrCl2·6H2O. Both systems belong to a simple eutectic type, and neither double salts nor solid solutions were formed. On the basis of Pitzer-Harvie-Weare model, the solubilities of the two systems at 288.15 K were demonstrated. A comparison showed that the calculated solubilities agreed well with the experimental data.

Measurements and Calculations of Stable Phase Equilibria in Ternary Systems MgSO4(Rb2SO4) + Cs2SO4 + H2O at T = 298.2 K

The components (solubilities and densities) in aqueous stable equilibria systems Cs2SO4 + MgSO4 + H2O and Rb2SO4 + Cs2SO4 + H2O at T = 298.2 K have been studied by the isothermal dissolution equilibrium method. The wet residue method and the X-ray diffraction method were used to confirm the solid phase compositions. The ternary system Cs2SO4 + MgSO4 + H2O is a complex saturated type, with the commensurate double salt Cs2SO4·MgSO4·6H2O formed at the investigated temperature. There are two two-salt cosaturation invariant points, with the coexisting solid phases corresponding to commensurate type saturation points E1 (MgSO4·7H2O + Cs2SO4·MgSO4·6H2O) and E2 (Cs2SO4·MgSO4·6H2O + Cs2SO4), three monovariant curves, and three crystallization fields in the system of Cs2SO4 + MgSO4 + H2O. The ternary system Rb2SO4 + Cs2SO4 + H2O with solid solutions formed contains two cosaturated points, with the equilibrium solid phases of the saturation points F1 and F2 corresponding to [(Rb, Cs)2SO4] + Cs2SO4 and Rb2SO4 + [(Rb,...

Solid–Liquid Phase Equilibria of the Ternary System (2-Naphthaldehyde + 4-Methylphthalic Anhydride + Ethyl Acetate) at (288.15, 298.15, and 308.15) K

The solubility of 2-naphthaldehyde (2-NA) and 4-methylphthalic anhydride (4-MA) in ethyl acetate at temperatures from 283.15 to 313.15 K and solid–liquid equilibrium of ternary (2-NA + 4-MA + ethyl acetate) system at temperatures of (288.15, 298.15, and 308.15) K were measured under pressure of 101.3 kPa. Three isothermal phase diagrams were plotted according to the ternary solubility data. For the ternary system, two pure 2-NA and 4-MA solids were formed at each temperature and determined by the wet residue method of Schreinemaker. The crystalline region of 2-NA decreases with the increase in temperature, and 4-MA is just the opposite. The crystallization region of 2-NA was found to be smaller than that of 4-MA. The solubility data of the system were correlated and calculated by NRTL and Wilson models. The results show that the NRTL model agrees well with the experimental data compared with the Wilson model. Furthermore, the densities of equilibrium solutions were determined at the corresponding temperatures.

Solid-liquid phase equilibria of ternary system Na2S2O3-Na2SO4-H2O in a wide range of temperatures: Measurement and application

Abstract In order to provide a fundamental basis for treatment of wastewater from desulfurization of coke oven gas to recover pure salt, solid-liquid equilibrium data of Na2S2O3-Na2SO4-H2O system at T = (278.15, 283.15, 291.15, 333.15 or 353.15) K were measured. The experimental data was obtained using the isothermal solution saturation method and Schreinemaker’s wet residue method. The solid-liquid phase diagrams of the ternary system were constructed. The ternary phase diagrams turned out to be simple eutectic type containing one invariant point, two univariant curves, and two single-salt crystallization regions. It was found that the crystallization region of Na2SO4 is larger than that of Na2S2O3 and expands with the increasing of temperature. But the crystallization region of Na2S2O3 decreases with the increasing of temperature. Through analyzing the thermodynamic characteristics of Na2S2O3 and Na2SO4, two crystallization methods for separating the mixture of Na2S2O3-Na2SO4 were put forward. A simple comparison of the two crystallization methods was carried out.