Solid-liquid phase equilibria of quaternary system NH4+//C1−, SO42−, H2PO4−–H2O and its subsystems NH4+//C1−, SO42−–H2O, NH4+//C1−, H2PO4−–H2O at 313.15 K. (September 2017)

• Record Type: Journal Article
• Authors: He, Tingting; Sun, Jiajin; Shen, Wei; Ren, Yongsheng
• Is Part Of: Journal of chemical thermodynamics. Volume 112(2017)
• Page Start: 31
• Page End: 42
• Publication Date: 2017-09
• Subjects: NH4Cl -- NH4H2PO4 -- Solid–liquid phase equilibrium -- Phase diagram -- Physico-chemical properties; Thermodynamics -- Periodicals; Thermochemistry -- Periodicals; Thermodynamique -- Périodiques; Thermochimie -- Périodiques; Thermochemistry; Thermodynamics; Periodicals; 541.369
• DOI: 10.1016/j.jct.2017.04.010
• Languages: English
• ISSNs: 0021-9614

Abstract

Graphical abstract: Dry-salt phase diagram of the quaternary system (NH4 + //C1 −, SO4 2−, H2 PO4 − –H2 O) at 313.15 K. S, pure solid of (NH4 )2 SO4 ; N, pure solid of NH4 Cl; P, pure solid of NH4 H2 PO4 ; E, invariant point of NH4 Cl and (NH4 )2 SO4 ; G, invariant point of NH4 Cl and NH4 H2 PO4 ; H, invariant point of (NH4 )2 SO4 and NH4 H2 PO4 ; F, quaternary invariant point of NH4 Cl, (NH4 )2 SO4 and NH4 H2 PO4 ; I, the equilibrium of salt (NH4 )2 SO4 with saturated solution. II, the equilibrium of salt NH4 H2 PO4 with saturated solution. III, the equilibrium of salt NH4 Cl with saturated solution. Highlights: Equilibrium data of NH4 + //C1 −, SO4 2−, H2 PO4 − and its subsystems were obtained. Dry-salt phase diagram and water diagram of the three systems are plotted. Diagrams of physic-chemical properties vs composition are plotted. Empirical equations are applicable to calculate theorized nD, η, ρ values. Abstract: Solid–liquid phase equilibrium and physical properties of ternary systems NH4 Cl-NH4 H2 PO4 -H2 O, NH4 Cl-(NH4 )2 SO4 -H2 O and quaternary system NH4 Cl-(NH4 )2 SO4 -NH4 H2 PO4 -H2 O at 313.15 K and atmospheric pressure were obtained by means of an isothermal solution method. The solid phases formed in the systems studied were determined by the Schreinemaker wet residue method. Based on the measured data, corresponding phase diagrams and the diagrams of physical properties versus composition were plotted. Neither complex salt nor solid solution is found in these systems at 313.15 K. The ternary phase diagram of NH4 + //C1 −, H2 PO4 − –H2 O contains one invariant point, and three crystallization regions (NH4 H2 PO4, NH4 Cl, and (NH4 Cl + NH4 H2 PO4 )). The ternary phase diagram of NH4 + //C1 −, SO4 2− –H2 O is similar to the previous one, also contains one invariant point, three crystallization regions ((NH4 )2 SO4, NH4 Cl, and (NH4 Cl + (NH4 )2 SO4 )). The quaternary phase diagram of NH4 + //C1 −, SO4 2−, H2 PO4 − –H2 O contains one quaternary invariant point, three crystallization regions ((NH4 )2 SO4, NH4 Cl, and NH4 H2 PO4 ), and crystallization field of NH4 H2 PO4 is the largest one of them. All results obtained in this work can be used for the stripping process of solvent extraction in the production of potassium dihydrogen phosphate.