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Highlights: [•] Determination of phase equilibrium of Na2SO4–MgSO4–(NH4)2SO4–H2O system at 25°C. [•] Phase diagram of this system was investigated and analyzed. [•] A new technology to produce Mg–N compound fertilizers was proposed. [•] The advantage of recycling mother liquid, steady production and energy saving. [ABSTRACT FROM AUTHOR]

Abstract: In order to develop a new process for concentrating and separating sodium sulfate (Na2SO4) and magnesium sulfate (MgSO4) of the bloedite by gas hydrate, the equilibrium of the ternary system H2O–Na2SO4–C3H8, H2O–MgSO4–C3H8 and the quaternary system H2O–Na2SO4–MgSO4–C3H8 with tetrahydrofuran (THF) additive were studied at 0°C. It showed that the mass percentage of Na2SO4 (MgSO4) in equilibrium liquid was higher than in feed. It proved that gas hydrate could be used to the concentration and separation of Na2SO4 and MgSO4. The solubility of the propane was calculated based on the Krichevsky–Kasarnovsky equation. The extended Pitzer model of electrolyte–electrolyte–nonelectrolyte–water system was derived and applied into H2O–Na2SO4–MgSO4–C3H8 system and its sub-systems. The necessary thermodynamic parameters had been derived from a least-squares optimization program. The model calculation value was in good agreement with experimental solubility for ternary and quaternary mixtures, which indicated that the Pitzer model could be successfully used to predict the phase equilibrium of the electrolyte–electrolyte–nonelectrolyte–water systems containing gas hydrate. [Copyright &y& Elsevier]

Abstract: In order to solve the difficult problem of powder P zeolite separation from solution disposed, a series of magnetic P zeolites are hydrothermally synthesized with traditional hydrothermal method by adding magnetic Fe3O4 particulates in the crystallization. The products were characterized with X-ray diffraction (XRD), scanning electron microscopy (SEM), IR spectrometer (IR), magnetic susceptibility, and ion exchange capability. The results show that the magnetism of the products is stable and magnetic susceptibility rises with the addition amount of Fe3O4 particulates increasing. Comparing the magnetic P zeolites synthesized with the pure P zeolite, their adsorption capabilities of Ca2+, Mg2+, K+ still are very high. When the magnetic zeolites are used to extract ion from solution disposed without molding, their powder products can be easily separated from solvent or solution by magnetic separation technology. [Copyright &y& Elsevier]

Based on the requirement of the new technology for producing Mg–N compound fertilizer by the reaction of MgCl 2 and (NH 4 ) 2 SO 4 , the phase equilibrium of the quaternary system Mg 2+ , NH 4 + //Cl − , SO 4 2− –H 2 O at 25 °C was studied. The solubilities of the quaternary system Mg 2+ , NH 4 + //Cl − , SO 4 2− –H 2 O were measured using isothermal method, and the phase diagram of this system was investigated. According to the phase diagram, there are nine solid phase crystalline zones, which correspond to MgSO 4 ·7H 2 O, MgSO 4 ·6H 2 O, MgSO 4 ·5H 2 O, MgSO 4 ·4H 2 O, (NH 4 ) 2 SO 4 , MgSO 4 ·(NH 4 ) 2 SO 4 ·6H 2 O, MgCl 2 ·6H 2 O, NH 4 Cl and MgCl 2 ·NH 4 Cl·6H 2 O respectively. MgSO 4 ·(NH 4 ) 2 SO 4 ·6H 2 O has the largest crystalline zone among these crystalline zones, which indicates that the double salt MgSO 4 ·(NH 4 ) 2 SO 4 ·6H 2 O is the easiest to crystallize out. Based on the analysis and calculation of the phase diagrams, the suitable conditions for the new technology were determined. The extended Pitzer model was derived and applied to the phase equilibrium calculation of system Mg 2+ , NH 4+ //Cl − , SO 4 2 –H 2 O and its sub-systems at 25 °C. The results showed that the calculated values were consistent with experimental results well. [ABSTRACT FROM AUTHOR]