2SO4 H2O Research Articles

Studies on Mutual Solubility of Salts in the NH4HCO3–(NH4)2SO4–H2O System

Mutual solubility of salts in a triple NH4HCO3–(NH4)2SO4–H2O system was studied in the temperature range of 293.15–323.15 K. The tests were performed using the isothermal solution saturation method...

Chemical changes and reaction mechanism of hardened cement paste–(NH4)2SO4–H2O system

Physical performance and chemical composition of some hydration products in hardened cement paste are changed considerably in presence of NH4+ ions, which is closely related to long term durability of cement concrete. The dissolution of some hydration products and the newly formed reaction products in such system were thus studied. The results showed that the concentration of dissolved Ca2+ ions were increased with the concentration of (NH4)2SO4 solution in external environment; when dissolution process was reached equilibrium, the main product was gypsum; while koktaite was also detected in condition of higher concentration of (NH4)2SO4 solution, which was usually ignored or mistaken as ettringite. In this case, gypsum crystals experienced significant morphology change with the deceasing of particle size when the concentration of (NH4)2SO4 solution was increased. Moreover, by the dissolving of Ca2+ ion, [SiO4]4− tetrahedral chains polymerized into network structure and NH4+ ions were supposed to be doped into C-S-H network structure.

Solubility Investigations in the MgSO4–Al2(SO4)3–(NH4)2SO4–H2O Quaternary System at 40 and 80 °C

The separation of magnesium and aluminum bearing compounds from the (NH4)2SO4 aqueous solution is crucial for the ammonium sulfate roasting technique to extract Mg and Al from the magnesium–aluminum-bearing slag. Equilibrium solubility data for the quaternary system of MgSO4–Al2(SO4)3–(NH4)2SO4–H2O at 40 and 80 °C were therefore measured and compared with those of their ternary subsystems of MgSO4–(NH4)2SO4–H2O and Al2(SO4)3–(NH4)2SO4–H2O, respectively. The mutual salting-out effect between MgSO4 and Al2(SO4)3 in the quaternary system was further discussed. On the basis of the measured data, a strategy for effective separation of magnesium and aluminum compounds from the MgSO4–Al2(SO4)3–(NH4)2SO4–H2O system was developed.

Phase equilibrium of the quaternary system K2SO4–MgSO4–(NH4)2SO4–H2O at 25 °C

The solubilities of the quaternary system K2SO4–MgSO4–(NH4)2SO4–H2O were measured by isothermal method at 25 °C and their dry salt phase diagrams were plotted. The results indicated that, at 25 °C, the solubility phase diagram of this quaternary system consists of seven crystallization regions, those are single-salt crystallization region MgSO4·7H2O, (NH4)2SO4, and K2SO4, complex salt crystallization region MgSO4·(NH4)2SO4·6H2O, MgSO4·K2SO4·6H2O, solid solution crystallization region (K1−n, NH4n)2SO4 (n:0.143–0.893) and (K1−n, NH4n)2SO4·MgSO4·6H2O (n:0.552–0.973), respectively. The extended Pitzer model was derived and applied to the phase equilibrium calculation of system K2SO4–MgSO4–(NH4)2SO4–H2O and its sub-systems at 25 °C. The results showed that the calculated values were consistent with experimental results well. The study on the quaternary system K2SO4–MgSO4–(NH4)2SO4–H2O provides a foundation for the N–Mg–K–S compound fertilizers preparation.

Phase Diagrams of the Na2SO4–MgSO4–(NH4)2SO4–H2O System at 60 °C and Their Application

The solubilities of quaternary system Na2SO4–MgSO4–(NH4)2SO4–H2O at 60 °C were measured by the isothermal method, and the corresponding phase diagram was studied. The analysis of the phase diagram shows that there are five crystalline fields, MgSO4·6H2O, Na2SO4·MgSO4·4H2O, Na2SO4, (NH4)2SO4, and MgSO4·(NH4)2SO4·6H2O, respectively. MgSO4·(NH4)2SO4·6H2O, and Na2SO4 crystalline fields are larger than other crystalline fields, which indicates that MgSO4·(NH4)2SO4·6H2O and Na2SO4 are crystallized out easily. On the basis of the analysis and calculation of the phase diagrams of the quaternary system Na2SO4–MgSO4–(NH4)2SO4–H2O and ternary system Na2SO4–(NH4)2SO4–H2O at 60 °C, a technology was designed to produce Mg–N compound fertilizers and Na2SO4 using (NH4)2SO4 as a salting-out agent to separate bloedite, which is easy to operate, fast to reach phases equilibrium, and can gain anhydrous Na2SO4 directly. On the basis of the Pitzer model of electrolyte solution theory, the solubilities of Na2SO4–MgSO4–(NH4)2SO4–H2O system at 60 °C were calculated. The results showed that calculated values were well consistent with experimental results.

Solid–Liquid Stable Equilibrium of the Aqueous Quaternary System NH4SCN–(NH4)2S2O3–(NH4)2SO4–H2O at 303.15 K

The salts of thiocyanate, thiosulfate, and sulfate exist in a variety of industrial processes such as textile, coking, and electroplating. The effluents from these industries cannot be discharged directly owing to their severe environmental pollution. In addition, there is an opportunity to recover significant commercial value from these effluents. The phase equilibria and phase diagram play a major role in separating and recovering useful resources. In this paper, the phase diagrams of the system NH4SCN–(NH4)2S2O3–(NH4)2SO4–H2O and its subsystems at 303.15 K were determined by an isothermal dissolution equilibrium method. In the phase diagram of the quaternary system, there is one invariant point, three univariant curves and three crystallized regions. The invariant point is cosaturated with ammonium thiocyanate, ammonium sulfate, and ammonium thiosulfate (NH4SCN + (NH4)2SO4 + (NH4)2S2O3). The three crystallization regions correspond to ammonium sulfate ((NH4)2SO4), ammonium thiocyanate (NH4SCN), and ammonium thiosulfate ((NH4)2S2O3). The first one is the largest area, but the latter two are much smaller ones. The phase diagram can be utilized to separate and recover NH4SCN, (NH4)2SO4, and (NH4)2S2O3 selectively and individually from the desulfurization effluents. The result of this paper shows that the environmental pollutant can be converted to the valuable product by a simple, economical, and green process.

Three-Liquid-Phase Extraction and Separation of Rare Earths and Fe, Al, and Si by a Novel Mixer–Settler–Mixer Three-Chamber Integrated Extractor

In the present work, three-liquid-phase extraction and separation of rare earths and Fe, Al, and Si by a novel mixer–settler–mixer three-chamber integrated extractor was investigated. Various three-liquid-phase systems (TLPSs) involving different organic extractants were employed to conduct continuous three-liquid-phase separation of rare earths and Fe, Al, and Si. In the TLPS of PC-88A/PEG 2000/(NH4)2SO4–H2O, light, middle, and heavy rare-earth ions had different distribution behaviors selectively into the organic top phase and salt-rich bottom phase, while most of Fe, Al, and Si were enriched into the poly(ethylene glycol) (PEG)-rich middle phase. Influences from aqueous pH values, agitation speeds, and flow ratios on three-liquid-phase partition behaviors of rare earths and Fe, Al, Si were evaluated. Experimental results indicated that an increase of the aqueous pH value facilitated the extraction of rare earths into the organic top phase and enrichment of Fe, Al, and Si into the PEG-rich middle phase. An increase of the agitation speed in three-phase mixer resulted in a change in the disappearance time of the dispersion band in a three-phase settler. The agitation speeds in a two-phase mixer and flow ratios of the organic phase to an aqueous biphasic mixture resulted in a change in the phase volumes of three-layered liquid flows in a three-phase settler so as to affect the partition behaviors of rare earths and Fe, Al, and Si. On the basis of analysis of the phase-forming behaviors of TLPSs and partition behaviors of rare earths and Fe, Al, and Si, the novel mixer–settler–mixer extractor is recommended for future application of continuous and countercurrent TLPE processes.

Removal of Al, Fe and Si from complex rare-earth leach solution: A three-liquid-phase partitioning approach

A new strategy was suggested to remove Fe, Al and Si impurities from rare-earth leach solution by controlling partitioning and selective enrichment of those impurities and rare earths in three-liquid-phase systems. Experimental results indicated that aqueous pH value and addition of water-soluble complexing agents or their mixtures into initial aqueous solution have significant influence on three-liquid-phase partitioning of Fe, Al, Si and rare earths. When only 1,10-phenanthroline was added, Fe and Si can be “filtered” into PEG-rich middle phase of three-liquid-phase system (Cyanex 272/PEG 2000/(NH4)2SO4–H2O) without affecting separation of heavy and light rare-earth ions in top organic and bottom salt-rich phase, respectively. Al remained in bottom phase. However, addition of EDTA and 1,10-phenanthroline promoted enrichment of Fe, Al and Si into PEG-rich middle phase, and almost all of rare earths were concentrated in salt-rich bottom phase. Those rare earths in salt-rich phase after removal of impurities can be further separated by another three-liquid-phase system of Cyanex 272/PEG 600/(NH4)2SO4–H2O. Heavy, middle and light rare earths, Yb, Eu and La, can be selectively enriched into different liquid phases. Therefore, separation of non-rare-earth impurities from rare earths, and then between light, middle and heavy rare earths can be achieved by two stages of three-liquid-phase partitioning. The present work highlights three-liquid-phase system can be a potential separation media for removal of Fe, Al, Si from complex rare-earth leach solution and group separation of different target metals into different liquid phases.

Phase diagrams of Na2SO4–MgSO4–(NH4)2SO4–H2O system at 25 °C and their application

Bloedite (Na2SO4·MgSO4·4H2O) is a kind of abundant natural resources. So far, it has not been developed and utilized effectively. In order to process and develop bloedite, a new technology to produce Na2SO4 and Mg–N compound fertilizers by a (NH4)2SO4 salting-out method to separate bloedite was proposed, the phase equilibrium of the quaternary system Na2SO4–MgSO4–(NH4)2SO4–H2O at 25°C was studied. The solubilities of the quaternary system Na2SO4–MgSO4–(NH4)2SO4–H2O were measured using isothermal method, and the phase diagram of this system was investigated. According to this phase diagram, there are six solid phases crystalline zones, which correspond to MgSO4·7H2O, MgSO4·Na2SO4·4H2O, Na2SO4·10H2O, Na2SO4·(NH4)2SO4·4H2O, (NH4)2SO4 and MgSO4·(NH4)2SO4·6H2O respectively. MgSO4·(NH4)2SO4·6H2O has the largest crystalline zone among these crystalline zones, which indicates that the double salt MgSO4·(NH4)2SO4·6H2O is the most easily to crystallize out. Based on the analysis and calculation of the phase diagrams, a new technology to produce Mg–N compound fertilizers and Na2SO4·10H2O using bloedite and (NH4)2SO4 as raw materials shows the advantage of non-evaporation of water and low energy consumption.

Phase Equilibrium of the Quaternary System Na2SO4–MgSO4–(NH4)2SO4–H2O at 0 °C

The solubilities of the ternary system MgSO4–(NH4)2SO4–H2O and the quaternary system Na2SO4–MgSO4–(NH4)2SO4–H2O at 0 °C were measured, and the phase diagrams of these two systems were plotted. On the basis of the phase diagrams obtained, we analyzed each saturation point and crystalline region. It indicated that ammonium sulfate as the salting-out agent can form double salt MgSO4·(NH4)2SO4·6H2O with magnesium sulfate, realizing better separation of sodium sulfate and magnesium sulfate. On the basis of the Pitzer model of electrolyte solution theory, the ionic strength function was introduced to express the interaction parameters between two kinds of electrolyte at 0 °C. The interaction parameters were regressed from the experimental data of the ternary systems, and the solubilities of Na2SO4–MgSO4–(NH4)2SO4–H2O system at 0 °C were calculated. The results showed that the calculated values were well consistent with experimental results.

Solubilities of NH4VO3 in the NH3–NH4+–SO42––Cl––H2O System and Modeling by the Bromley–Zemaitis Equation

The solubility of ammonium metavanadate (NH4VO3) in ammonium salt solution is significant for the precipitation of NH4VO3from the vanadium-containing solution. The solubilities of NH4VO3 in the (NH4)2SO4–H2O, NH4Cl–H2O, and (NH4)2SO4–NH3–H2O systems were measured using dynamic method in the temperature range from (298 to 343) K. The investigated concentration is up to 3.0 mol·kg–1, 2.5 mol·kg–1, and 5.2 mol·kg–1 for (NH4)2SO4, NH4Cl, and NH3, respectively. The solubility of NH4VO3 decreases sharply with the addition of (NH4)2SO4 or NH4Cl while the solubility of NH4VO3 in the mixed NH3 and (NH4)2SO4 (0.10 mol·kg–1) solution increases first and then levels off with increasing NH3 concentration. The solubility product constant (KSP) of NH4VO3 was also determined using the standard-state thermodynamic data. The Bromley–Zemaitis model was applied to model the solubility of NH4VO3 in the systems mentioned above, and five pairs of new model parameters were obtained via the regression of the experimental solubili...

Both initial concentrations of Fe(II) and monovalent cations jointly determine the formation of biogenic iron hydroxysulfate precipitates in acidic sulfate-rich environments

In order to accurately predict the types of biogenic iron hydroxysulfate precipitates in acidic, sulfate-rich environments facilitated by Acidithiobacillus ferrooxidans, different initial concentrations of Fe2+, K+, Na+, and NH4+ are selected and tested in batch experiments for the formation of the precipitates. The critical equations of jarosite formation in FeSO4–K2SO4–H2O system or FeSO4–(NH4)2SO4–H2O system could be described as Y=−22120.8077−0.04257x+0.006170x2 (R2=0.9979) or Y=0.03540−0.002950x+7.407E−5x2 (R2=0.9934), respectively, where Y is the threshold or critical values of the molar ratio of Fe/K or Fe/NH4 for jarosite formation, and x (mmol/L) is the initial concentration of Fe(II). Schwertmannite is the sole biogenic secondary ferric mineral when molar ratio of Fe/K or Fe/NH4 is higher than Y in the system with a given initial Fe(II) concentration. The precipitates are an admixture of schwertmannite and jarosite, or pure jarosite when the Fe/M molar ratio is lower than Y. The crystallinity of the secondary ferric minerals increased with the increase of initial Fe(II) concentration in the medium with a fixed K+ concentration. It is observed that the capacity of monovalent cation in promoting jarosite formation is K+>NH4+>Na+, as exhibiting that the capacity of K+ in this process is about 75 and 200 times greater than NH4+ and Na+, respectively. Obviously, both the initial concentration of Fe(II) and molar ratio of Fe to monovalent cation determine the types of biogenic iron hydroxysulfate precipitates.

Leaching of hemimorphite in NH3–(NH4)2SO4–H2O system and its mechanism

The leaching process and evolution of the leaching residue of pure hemimorphite in an NH3–(NH4)2SO4–H2O system were investigated. The results show that in the leaching process, zinc rapidly dissolved in an NH3–(NH4)2SO4–H2O system when it existed as a hemimorphite. Zinc and silica in hemimorphite simultaneously dissolved in the solution, and amorphous silica was then precipitated from the leaching solution. The leaching efficiency of zinc reached 95%, whereas most of the silicon remained in the residue. The leaching residue exists in the form of amorphous silica based on the results of the thermogravimetric analysis, differential scanning calorimetry, Fourier transform infrared spectroscopy, X-ray diffraction, scanning electron microscopy, and energy dispersive spectroscopy. Thus, the hemimorphite leaching process and mechanism in an NH3–(NH4)2SO4–H2O systems were determined.

Some Physicochemical Parameters of Saturated Ternary Solutions of Systems with Mixed Crystals in their Solid Phase

AbstractThe measurements of density (ϱ), viscosity (η) and hydration number (nh) of saturated solutions of ternary systems KClKBrH2O, K2SO4(NH4)2SO4H2O and KNO3NH4NO3H2O with mixed crystals in the solid phase have been conducted. It has been confirmed, that the occurence of the extremes on the curves of dependence of the properties (ϱ, η, nh) on the composition of saturated solution may be the base for the supposition that beside mixed crystals the double salts have also been formed in the solid phase of a given system.

The significance of X‐ray investigations for the classification of multicomponent systems with mixed crystals in a solid phase

AbstractThe X‐ray investigations of solid phases in the multicomponent systems KClKBrH2O, K2SO4(NH4)2SO4H2O and KNO3NH4NO3H2O were conducted and the crystal lattice parameters of mixed crystals forming in these systems were determined. It was confirmed that in the KClKBrH2O system the continuous solid solutions were formed and in the K2SO4(NH4)2SO4H2O system the solid solutions with a miscibility gap were formed. In the KNO3NH4NO3H2O system the presence of two series of mixed crystals, namely the mixed crystals between ammonium nitrate and the double salt KNO3 · 2 NH4NO3 and between potassium nitrate and the same double salt was confirmed. In this system a wide region of discontinuity (for xNH4NO3 = 0.083 – 0.67) also occurred.According to Roozeboom's classification, the KClKBrH2O system belongs to the 3rd type, the K2SO4(NH4)2SO4H2O to the 5th type (the discontinuous mixed crystals, the systems of peritonic type) and the KNO3NH4NO3H2O system is not comprised in this classification.

Complexes of N-(2-benzothiazole)2-pyridinaldimine with CO II and Ni II salts

The following complexes of N-(2-benzothiazole)-2pyridinaldimine (L) with Co II and Ni II salts have been isolated: Co(L) 2(ClO 4) 22H 2O, Co(L) 2(NO 3) 2H 2O, Co(L) 2SO 4H 2O, Ni 2(L) 4Cl 4H 2O, Ni(L) 2(CH 3COO) 2H 2O, Ni(L) 3(ClO 4) 22H 2O, Ni(L) 2(NO 3) 2H 2O. The ligands acts as a bidentate chelating agent trough both nitrogen atoms of the 2-pyridinaldimine system. The electronic spectra and magnetic properties are consistent with an octahedral coordination for all the complexes. The infrared spectra (40000-250 cm −1) of the ligands as well as those of Co II and Ni II complexes are also discussed.

Contribution à l'étude du système quaternaire K+—NH4+—CrO4−−—SO4−−—H2O: I. les isothermes de 25° des systèmes ternaires limites

AbstractThe four ternary limiting isotherms of the system K+− NH4+CrO4−−SO4−−H2O are given for 25° C. In the systems K2SO4(NH4)2SO4H2O and K2SO4K2CrO4H2O only one solid phase has been encountered; both systems belong to the type I of the ROOZEBOOM classification. A miscibility gap is present in the systems (NH4)2CrO4K2CrO4H2O and (NH4)2CrO4(NH4)2SO4H2O; they belong to ROOZEBOOM'S type V.

CCCXVII.—Equilibrium in the systems MnSO4–K2SO4–H2O and MnSO4–(NH4)2SO4–H2O at 0°; also in the system CuSO4–Na2SO4–H2O at 0°, 25°, and 37·5°

CCCXVII.—Equilibrium in the systems MnSO₄–K₂SO₄–H₂O and MnSO₄–(NH₄)₂SO₄–H₂O at 0°; also in the system CuSO₄–Na₂SO₄–H₂O at 0°, 25°, and 37·5°