K⁺//Cl^-,H₂PO₄^-,(NH ₂) ₂CO-H₂O And NH₄⁺,K< Sup>+//Cl^-,(NH₂)₂CO-H₂O The System Was Studied In Pha

The multicomponent solid-liquid phase equilibrium is the basis of the study on the material crystallization process.In order to provide a theoretical basis for the solid-liquid phase equilibria of the quinary system NH₄⁺,K⁺//Cl^-,H₂PO₄^-,（NH₂）₂CO-H₂O and co-crystallization process study,the phase equilibria of the four ternary systems and three quaternary systems under the quinary system NH₄⁺,K⁺//Cl^-,H₂PO₄^-,（NH₂）₂CO-H₂O at 353.15 K were studied by an isothermal solution equilibrium method.These details are as follows:（1）Solid-liquid phase equilibria of the three ternary systems KCl-KH₂PO₄-H₂O、KCl-（NH₂）₂CO-H₂O、KH₂PO₄-（NH₂）₂CO-H₂O and the quaternary system K⁺//Cl^-,H₂PO₄^-,（NH₂）₂CO-H₂O at 353.15 K were studied by an isothermal solution equilibrium method.The composition of solid phase at equilibrium state was also verified by wet residue method and X-ray diffraction.The equilibrium phase diagram of three ternary system and the equilibrium phase,the water content diagram of the quaternary system at 353.15 K were plotted respectively.The research results show that the ternary system KCl-KH₂PO₄-H₂O at 353.15K is a simple co-saturation type,and there is no solid solution and double salt formation.The system phase diagram of KCl and KH₂PO₄,a crystallization region of KCl,a crystallization region of KH₂PO₄ and a unsaturated region.The are a of KH₂PO₄ crystallization field is much larger than that of KCl.KCl has a strong salting-out effect on KH₂PO₄,and KH₂PO₄ has a weak salting-out effect on KCl.The equilibrium solid phase of the ternary system is a mixture of KH₂PO₄ and KCl.The research results show that the ternary system KCl-（NH₂）₂CO-H₂O at 353.15K is a simple co-saturation type,and there is no solid solution and double salt formation.The system phase diagram contains one invariant point,two univariant curves and four regions which include a co-crystallization zoneof KCl and（NH₂）₂CO,a crystallization region of KCl,a crystallization region of（NH₂）₂CO and a unsaturated region.The are a of KCl crystallization field is much larger than that of（NH₂）₂CO.CO（NH₂）₂ has a certain salting-in effect on KCl,and KCl also has a certain salting-in effect on（NH₂）₂CO.The equilibrium solid phase of the ternary system is a mixture of（NH₂）₂CO and KCl.The research results show that the ternary system KH₂PO₄-（NH₂）₂CO-H₂O at353.15 K is a simple co-saturation type,and there is no solid solution and double salt formation.The system phase diagram contains one invariant point,two univariant curves and fourregions which include a co-crystallization zone of KH₂PO₄ and（NH₂）₂CO,a crystallization region of KH₂PO₄,a crystallization region of（NH₂）₂CO and a unsaturated region.The are a of KH₂PO₄ crystallization field is much larger than that of（NH₂）₂CO.KH₂PO₄ has a certain salting-out effect on（NH₂）₂CO,and（NH₂）₂CO has a strong salting-in effect on KH₂PO₄.The equilibrium solid phase of the ternary system is a mixture of（NH₂）₂CO and KH₂PO₄.The research results show that the quaternary system K⁺//Cl^-,H₂PO₄^-,（NH₂）₂CO-H₂O is a simple eutectic type.The system has one invariant point(the equilibrium solid phase is a mixture of KCl,KH₂PO₄ and（NH₂）₂CO,three univariate curves and three crystallization regions which include a crystallization region of KH₂PO₄,a crystallization region of（NH₂）₂CO and a crystallization region of KCl.The size of the crystallization area is:KCl crystallization area>KH₂PO₄ crystallization area>（NH₂）₂CO crystallization area.The solubility of（NH₂）₂CO is the largest,followed by the solubility of KH₂PO₄,and the solubility of KCl is the smallest in the quaternary system.（2）Solid-liquid phase equilibria of the ternary systems KH₂PO₄-NH₄H₂PO₄-H₂O and the reciprocal quaternary system NH₄⁺,K⁺//Cl^-,H₂PO₄^--H₂O at 353.15 K were studied by an isothermal solution equilibrium method.The equilibrium phase diagram of ternary system and the equilibrium phase,the water content diagram of the quaternary system at 353.15 K were plotted respectively.The research results show that the ternary system KH₂PO₄-NH₄H₂PO₄-H₂O at353.15 K forms two solid solutions.The phase diagram consists of one co-saturation point,two univariate curves and six regions.The two univariate curves are KH₂PO₄solubility curve and NH₄H₂PO₄ solubility curve respectively.The phase diagram has six phase zones,including a crystallization region of KH₂PO₄,a crystallization region of NH₄H₂PO₄,a crystallization region of（NH₄,K）H₂PO₄ solid solution,a crystallization region of（K,NH₄）H₂PO₄ solid solution,a co-crystallization zoneof（NH₄,K）H₂PO₄ and（K,NH₄）H₂PO₄,and a unsaturated region.The research results show that the phase diagram of the reciprocal quaternary system K⁺,NH₄⁺//Cl^-,H₂PO₄^--H₂O at 353.15 K consists of two co-saturation points,five univariate curves and four crystallization regions.The size of crystallization region is as follows:crystallization region of（NH₄,K）H₂PO₄ solid solution is the largest,the smallest is crystallization region of（NH₄,K）Cl solid solution,which indicates that the solubility of（NH₄,K）Cl solid solution is the largest,the solubility of（NH₄,K）H₂PO₄ solid solution is the smallest in this system.（3）Solid-liquid phase equilibria of the quaternary system NH₄⁺,K⁺//Cl^-,CO（NH₂）₂-H₂O at 353.15 K were studied by an isothermal solution equilibrium method.The equilibrium phase and water content diagram of quaternary system at353.15 K were plotted according to solubility data.The research results show that the quaternary system NH₄⁺,K⁺//Cl^-,（NH₂）₂CO-H₂O contains double salt and solid solution.In the system,（NH₂）₂CO and NH₄Cl form CO（NH₂）₂·NH₄Cl double salt,NH₄Cl and KCl form two solid solution（K,NH₄）Cl and（NH₄,K）Cl.Phase diagram of the quaternary system consists of three co-saturation points,four univariate curves and four crystallization regions,including a crystallization region of CO（NH₂）₂,a crystallization region of KCl-based（K,NH₄）Cl solid solution,a crystallization region of NH₄Cl-based（NH₄,K）Cl solid solution,a co-crystallization zoneof（K,NH₄）Cl solid solution and（NH₂）₂CO·NH₄Cl double salt.