Ternary Systems. XX. Calcium Sulfate, Ammonium Sulfate and Water

Hill, Arthur E.; Yanick, Nicholas S.

doi:10.1021/ja01307a014

Cited by 21 publications

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“…The solubility behavior of the CaSO 4 –(NH 4 ) 2 SO 4 –H 2 O system is very complicated because of the presence of hydrates (dihydrate, hemihydrate, and anhydrite) and double salts (monocalcium salt, dicalcium salt, and pentacalcium salt). Hill and Yanick presented a systematic study on the solubility of all solid phases mentioned above except hemihydrate in CaSO 4 –(NH 4 ) 2 SO 4 –H 2 O system from 25 to 100 °C with (NH 4 ) 2 SO 4 concentration between 0 and saturation . Their data are adopted to evaluate the NRTL binary interaction parameters for the pair between electrolytes (Ca + , SO 4 2– ) and (NH 4 + , SO 4 2– ).…”

Section: Results and Discussionmentioning

confidence: 99%

“…Figure presents a comparison of the model calculations and the experimental results of Hill and Yanick on solubility of dihydrate, anhydrite, monocalcium, dicalcium, and pentacalcium as a function of (NH 4 ) 2 SO 4 molality at 25, 50, 75, and 100 °C, respectively. The solubility of hemihydrate predicted by the model at 75 and 100 °C is also plotted for comparison.…”

Section: Results and Discussionmentioning

confidence: 99%

“…Experimental data of Hill et al (symbols) for solubility of dihydrate, anhydrite, monocalcium salt, dicalcium salt, and pentacalcium salt in aqueous (NH 4 ) 2 SO 4 solution and the model calculations (lines) at 25, 50, 70, and 100 °C, respectively.…”

Section: Results and Discussionmentioning

confidence: 99%

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Thermodynamic Modeling of CaSO₄–(NH₄)₂SO₄–NH₃–H₂O Quaternary System with Asymmetric E-NRTL Model

Pan

Liu

Qin

et al. 2019

Ind. Eng. Chem. Res.

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Ammonium sulfate [(NH 4 ) 2 SO 4 ], an undesired byproduct in the caprolactam process, can be converted into recyclable NH 3 by the substitution reaction with lime milk to reduce the ammonia consumption and produce high-quality gypsum. However, the thermodynamic mechanism of this process has not been clarified, which results in the unpredictable crystal phase of calcium sulfate products. In this work, a thermodynamic model for the CaSO 4 −(NH 4 ) 2 SO 4 −NH 3 −H 2 O quaternary system with the asymmetric E-NRTL activity coefficient model was developed to understand the thermodynamic behavior. The modeling works involved the data fitting of binary solubility, osmotic coefficient, enthalpy of solution, and heat capacity data as well as ternary solubility data. It was shown that the model could predict the solubility of ammonia and calcium sulfate in aqueous ammonium sulfate solution with temperature ranging from 0 to 160 °C and pressure up to 1.0 MPa. Furthermore, the constructed model for the quaternary system was proved to be reliable for predicting the phase transition behavior of solid CaSO 4 in the electrolyte mixtures of (NH 4 ) 2 SO 4 −NH 3 −H 2 O solution. For the regeneration process of NH 3 from ammonium sulfate, this work will offer a reliable model for the reactors design and process optimization.

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Section: Results and Discussionmentioning

confidence: 99%

Section: Results and Discussionmentioning

confidence: 99%

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Thermodynamic Modeling of CaSO₄–(NH₄)₂SO₄–NH₃–H₂O Quaternary System with Asymmetric E-NRTL Model

Pan

Liu

Qin

et al. 2019

Ind. Eng. Chem. Res.

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“…CaSO 4 ·2H 2 O is a sparingly soluble salt. The nature of the solvent, temperature, pH, and ionic concentration are some of the factors responsible for gypsum solubility. − The solubility of CaSO 4 ·2H 2 O slightly increases with an increase of temperature, attains a maximum, and then decreases with a further increase in temperature. , Because of very low solubility, several times CaSO 4 ·2H 2 O precipitates out and deposits on the surfaces of equipment wherein brine solution containing calcium and sulfate ions is processed. These deposits (scale) reduce the efficiency of industrial processes and affect the life of equipment severely .…”

Section: Introductionmentioning

confidence: 99%

“…Extensive research has been carried out on CaSO 4 ·2H 2 O solubility in aqueous or aqueous salt solutions. − In the case of sodium chloride solutions (brines), the solubility of CaSO 4 ·2H 2 O increases up to a certain concentration, attains a maximum value, and then decreases with a further increase in concentration. The effects of inorganic salts or organic additives on CaSO 4 ·2H 2 O dissolution in aqueous or aqueous NaCl solutions have also been investigated by several researchers. − Aliphatic alcohols are well-known for their antisolvent crystallization activity.…”

Section: Introductionmentioning

confidence: 99%

Effects of Aliphatic Alcohols on Solubility, Physicochemical Properties, and Morphology of Calcium Sulfate Dihydrate (Gypsum) in Aqueous Sodium Chloride Solution at 35 °C

2019

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The effect of addition of aliphatic alcohols (methanol, ethanol, and isopropyl alcohol) on the dissolution characteristics of calcium sulfate dihydrate (gypsum, CaSO4·2H2O) in brines has been studied at 35 °C. Addition of alcohols decreased the dissolution of CaSO4·2H2O in aqueous NaCl solutions significantly and also shifted its solubility maximum toward a lower concentration of NaCl. We have also recorded the density (ρ) and speed of sound (u) for the quaternary systems (CaSO4·2H2O + NaCl + alcohols + H2O) at 35 °C. Using primary data, we derived the isentropic compressibility (κS) of the solutions. The experimentally determined physical and derived properties have been correlated using polynomial or linear fits using the method of least-squares. The crystal growth behavior and morphology of gypsum cocrystallized with NaCl crystals from different solutions has also been examined. Alcohol additives seem to be an environmentally friendly, low-cost additive to decrease the solubility of gypsum in aqueous systems with or without NaCl.

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Studies of the effects of electrolytes on the rates of precipitation of calcium sulphate dihydrate using an ion‐selective electrode

Mile

Vincent

Wilding

1982

J. Chem. Technol. Biotechnol.

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A calcium ion selective electrode has been used to follow the acceleration of the rate of precipitation of calcium sulphate dihydrate by inorganic electrolytes at 15, 25 and 35°C. At zero and low added electrolyte concentrations, the rate of precipitation is strictly proportional to the square of the supersaturation, has an activation energy 75 kJ mol-' in agreement with previous studies and is indicative of a surface diffusion controlled process. However, with electrolytes containing sulphate ions in excess of 0.05 mol dm-3 marked departures from a square law are observed; the rate is best represented as the sum of a square and first order term in supersaturation, the first order term becoming dominant at concentration of c. 0.1 mol dnr3. Under these conditions the rate has an activation energy (29 kJ mol-l) which is close to that for the volume diffusion of ions in aqueous solutions and indicates that the surface process has been accelerated to such an extent that the diffusion of ions from solution to the crystal face has become the slowest and, hence, the rate controlling step. It appears that the electrolytes accelerate the surface process by increasing the rates of dehydration of the calcium and sulphate ions at the interface.

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Ternary Systems. XX. Calcium Sulfate, Ammonium Sulfate and Water

Cited by 21 publications

References 0 publications

Thermodynamic Modeling of CaSO₄–(NH₄)₂SO₄–NH₃–H₂O Quaternary System with Asymmetric E-NRTL Model

Thermodynamic Modeling of CaSO₄–(NH₄)₂SO₄–NH₃–H₂O Quaternary System with Asymmetric E-NRTL Model

Effects of Aliphatic Alcohols on Solubility, Physicochemical Properties, and Morphology of Calcium Sulfate Dihydrate (Gypsum) in Aqueous Sodium Chloride Solution at 35 °C

Studies of the effects of electrolytes on the rates of precipitation of calcium sulphate dihydrate using an ion‐selective electrode

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Ternary Systems. XX. Calcium Sulfate, Ammonium Sulfate and Water

Cited by 21 publications

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Thermodynamic Modeling of CaSO4–(NH4)2SO4–NH3–H2O Quaternary System with Asymmetric E-NRTL Model

Thermodynamic Modeling of CaSO4–(NH4)2SO4–NH3–H2O Quaternary System with Asymmetric E-NRTL Model

Effects of Aliphatic Alcohols on Solubility, Physicochemical Properties, and Morphology of Calcium Sulfate Dihydrate (Gypsum) in Aqueous Sodium Chloride Solution at 35 °C

Studies of the effects of electrolytes on the rates of precipitation of calcium sulphate dihydrate using an ion‐selective electrode

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Thermodynamic Modeling of CaSO₄–(NH₄)₂SO₄–NH₃–H₂O Quaternary System with Asymmetric E-NRTL Model

Thermodynamic Modeling of CaSO₄–(NH₄)₂SO₄–NH₃–H₂O Quaternary System with Asymmetric E-NRTL Model