SOLUBILITY AND PHASE EQUILIBRIUM OF AN WATER SYSTEM - POTASSIUM, MAGNESIUM, CALCIUM SALTS CARBONATES AT A TEMPERATURE OF 25°C

UDC: 541. 123.6

SOLUBILITY AND PHASE EQUILIBRIUM OF AN WATER SYSTEM - POTASSIUM, MAGNESIUM, CALCIUM SALTS CARBONATES AT A TEMPERATURE OF 25°C

(K⁺,Mg²⁺,Ca²⁺//CO₃^2--H₂O)

Umaralii S., Usmonov M.B.

Tajik State Pedagogical University named after S. Ayni

Multicomponent water-salt systems are the composition of many natural and technical objects that are the subject of research in the field of chemistry, mineralogy and technology. The main method for studying chemical systems is physicochemical analysis, which can be used to determine the laws of interaction of their components and construct their state or solubility diagrams. State diagrams of chemical systems are an expression of the relationship between the properties of substances (melting, solubility, etc.) and the influence of external factors (temperature, pressure, etc.) [1]. The founder of this discipline, N.S. Kurnakova, played a great role in developing the theory of the foundations of physicochemical analysis [2]. N.S.

Kurnakov was the first to define the main tasks of physicochemical analysis as a scientific theory. N.S. Kurnakov determined that physicochemical analysis is one of the parts of chemistry that studies the relationship between the composition and measurable properties of chemical systems, as a result of which a state and a basic diagram are created. N.S. Kurnakov became Yakusin and proposed the basic principles of physicochemical analysis, the principles of compatibility and consistency. The schematic method of studying the structure of facies diagrams played a very important role in the further development of the theory of the foundations of physical and chemical analysis. The study of multicomponent chemical systems is primarily due to the fact that existing methods do not allow for a visual display of the studied multicomponent systems using existing three-dimensional geometric figures, the implementation of experimental work requires a large amount of effort, time and chemical materials, since the determination of solid phases in equilibrium is difficult, etc.

Yu. G. Goroshchenko proposed the third principle of physicochemical analysis - the compatibility principle, according to which the displacement of the geometric elements of the component (n-component) in the direction of the general system (n+1-component) should be justified from a scientific and theoretical point of view [3]. Based on this principle, L. Soliev developed a new method for studying multicomponent chemical systems, called the translation method. It was proposed and accepted by specialists as one of the universal methods for studying multicomponent chemical systems [1].

The purpose of monitoring phase equilibria and solubility in chemical systems is to identify their interactions based on test results and create conditions for creating a real diagram of their phase equilibria. Only on the basis of such diagrams can we obtain complete information about the chemical systems under study. The four-component system K+, Mg2+, Ca2+//CO32--H2O is one of the components of the five-component system K+, Mg2+, Ca2+//SO42-, CO32--H2O, which is part of industrial waste, including liquid waste from the aluminum industry [4-7]. The process of crystallization of these salts in an aqueous solution of waste is determined by the laws of phase balance of the six-component system Na+, Ca2+ //SO42-, CO32-, HCO3-, F--H2O and its five- and four-component system.

In this article, the solubility of a system consisting of potassium, magnesium and calcium carbonates formed with water at a temperature of 250C is investigated. Previously [8,9] we determined the phase equilibria of this system using the translation method and constructed a phase equilibria diagram.

The components of this chemical system consist of potassium, magnesium and calcium carbonates, which at a temperature of 250C in the form of CaSO3 – calcite (Cs); K2CO3 1.5-(K∙1.5); СаСО3 MgСО3-dolomite (Ca∙Mg) MgСО3 3H2O-magnesite (Mg 3); K2CO3 СаСО3-(K∙Са) crystallize. The following salts were used for the experiment: СаСО3 (chemically pure); MgСО3 3H2O (by chemical purity); K2SO3 (pure); the experiment was carried out using the saturation method [10-11].

Based on literature data [12,13], we previously prepared a solution for the invariant points of the following three-component systems of this four-component system at a temperature of 25 °C: K +, Mg2 +, // CO32 -- H2O, K +, Ca2 + // CO32 -- H2O and Mg2 +, Ca2 + // CO32 -- H2O. Then, using the translation method, the invariant points of the three-component level are transferred to the four-component level [8], their high solubility at a temperature of 25 °C is established, and then they are separated. The solution was stirred using a magnetic stirrer and the temperature was controlled by a contact thermometer connected to a U-8 thermostat, the accuracy of which is ±0.10 °C. Mixing was carried out for 80-120 hours. Crystallization of solid phases was observed using a Micromed C 11 microscope, and after equilibration, the solid phases were photographed using a SONY-DSC-S500 camera.

Fig. 1. Photomicrograph of the equilibrium solid phase of the system

K⁺, Mg²⁺,Ca²⁺//CO₃^2--H₂O,, for a temperature of 25^o

Separation of the solid and liquid phases was carried out through a Buchner funnel connected to a vacuum pump. Then the solid phase was washed with 96% ethyl alcohol and dried at 120°C. Chemical analysis was carried out using known methods [14-17]. Optical analysis of crystals [18] with their solid phases is shown in Figure 1, and the result of chemical analysis of the native solution is presented in Table 1.

Table 1. Solubility of nonvariant points of the K⁺, Mg²⁺,Ca²⁺//CO₃^2--H₂O

system at a temperature of 25^oC

	Liquid phase composition. with %				Equilibrium solid phases
	K₂CO₃	CaCO₃	MgCO₃	H₂O	Equilibrium solid phases
L₁	52,740	-	-	42,260	К∙1,5
L₂	-	0,004	-	99,995	Сс
L₃	-	-	0,022	99,977	Mg∙3
	-	0,007	0,024	99,968	Сс + Ca∙Mg
	-	0,004	0,038	99,957	Ca∙Mg+ Mg∙3
	46,786	0,005	-	53,209	Сс+ К∙Сa
	57,916	0,004	-	42,079	К∙Сa+ К∙1,5
	55,930	-	0,012	44,058	К∙1,5+ Mg∙3
	61,110	0,007	0,018	38,700	Сс+ Ca∙Mg+ К∙Сa
	45,764	0,004	0,025	54,206	Ca∙Mg+ К∙1,5+ Mg∙3
	60,108	0,005	0,025	39,860	Ca∙Mg+ К∙1,5+ К∙Сa

Based on the obtained data, a solubility diagram of the K+, Mg2+, Ca2+//CO32--H2O system for a temperature of 25 °C was constructed, which is shown in Figure 2 (a) water-salt part b) salt part).

Figure 2. Solubility diagram of the K⁺,Mg²⁺,Ca²⁺//CO₃^2--H₂O system at a temperature of 25^oC a) water-salt part b) salt part

The mass-centric method was used to determine the location of the non-variant points of the three-component () and four-component () levels, where n is the number of digits. Due to the low solubility of salts, its ratio with water is 1:5. The positions of the three- and four-component non-variant points on the diagram are determined based on solubility data using the mass-centric method [19] by the following calculations.

1.For a point with equilibrium solid phases Сс+Сa·Mg

2.For a point with equilibrium solid phases Сa·Mg+Mg·

3.For a point with equilibrium solid phases Сс+K·1,5

4.For a point with equilibrium solid phases K·Ca+K·1,5

5.For a point with equilibrium solid phases K·1,5+Mg·3

6.For a point with equilibrium solid phases Сс+K·Ca +Ca·Mg

7.For a point with equilibrium solid phases K·1.5+Ca·Mg+ Mg·3

8.For a point equilibrium solid phases K·Ca+ K·1,5 + Сa·Mg

Fig. 2 shows the general part (a) and the salt part (b) of the solubility diagram of the K+, Mg2+, Ca2+//CO32--H2O system at a temperature of 25°C, which reflects the position of crystallization of the corresponding equilibrium phases. As can be seen from Fig. 2, for this four-component system at a temperature of 25°C, the region of crystallization of calcite (CaCO3) occupies most of it, which shows the low solubility of this salt under these conditions. Its geometric shapes (squares, dots and lines) are presented in Table 2.

Table 2. List of geometric forms of the K⁺,Mg²⁺,Ca²⁺//CO₃^2--H₂O

diagram for a temperature of 25^oC

Geometric elements	Decoding the signs
е₁	Solubility of potassium carbonate in water
е₂	Solubility of calcium carbonate in water
е₃	Solubility of magnesium carbonate in water
	Crystallization point Сс+Сa·Mg in the system Mg²⁺,Ca²⁺//CO₃^2--H₂O
	Crystallization point Сa·Mg+ Mg·3 in the system Mg²⁺,Ca²⁺//CO₃^2--H₂O
	Crystallization point Сс+K·1,5 in the system K⁺,Ca²⁺//CO₃^2--H₂O
	Crystallization point K·Ca+K·1,5 in the system K⁺,Ca²⁺//CO₃^2--H₂O
	Crystallization point K·1,5+Mg·3 in the system K⁺,Mg²⁺//CO₃^2--H₂O
	The co-crystallization point of K·Ca+Сс+ Сa·Mg in the system K⁺,Mg²⁺,Ca²⁺//CO₃^2--H₂O
	The co-crystallization point of K·1,5+Mg·3+ Сa·Mg in the system K⁺,Mg²⁺,Ca²⁺//CO₃^2--H₂O
	The co-crystallization point of K·Ca+ K·1,5 + Сa·Mg in the system K⁺,Mg²⁺,Ca²⁺//CO₃^2--H₂O
е₁-	Crystallization point K·1,5 in the system K⁺,Ca²⁺//CO₃^2--H₂O
е₁-	Crystallization point K·1,5 in the system K⁺,Mg²⁺//CO₃^2--H₂O
е₂-	Crystallization point Сс in the system Mg²⁺,Ca²⁺//CO₃^2--H₂O
е₂-	Crystallization point Сс in the system K⁺,Ca²⁺//CO₃^2--H₂O
е₃-	Crystallization point Mg·3 in the system Mg²⁺,Ca²⁺//CO₃^2--H₂O
е₃-	Crystallization point Mg·3 in the system K⁺,Mg²⁺//CO₃^2--H₂O
-	The co-crystallization point of Сс+ Сa·Mg дар системаи Mg²⁺,Ca²⁺//CO₃^2--H₂O
-	The co-crystallization point of Сa·Mg+ Mg·3 in the system Mg²⁺,Ca²⁺//CO₃^2--H₂O
-	The co-crystallization point of K·Ca+ K·1,5 in the system K⁺,Ca²⁺//CO₃^2--H₂O
-	The co-crystallization point of K·Ca+ Сс in the system K⁺,Ca²⁺//CO₃^2--H₂O
-	The co-crystallization point of Mg·3 + K·1,5 in the system K⁺,Mg²⁺//CO₃^2--H₂O
е₁- - - - -е₁	Field of crystallization K·1,5
е₂- - - -е₂	Field of crystallization Сс
е₃- - - -е₃	Field of crystallization Mg·3
- - -	Field of crystallization K·Cа
- - - - -	Field of crystallization Сa·Mg

CONCLUSION

1.First, the solubility of the K+,Mg2+,Ca2+//CO32--H2O system was studied at a temperature of 25oC, and a diagram of its solubility was created for this temperature.

The list of coordinates of the geometric forms of the K+,Mg2+,Ca2+//CO32--H2O system is established at the given temperature.
The micrograph of the equilibrium solid phases of this system for a temperature of 25oC is given.
It was determined experimentally that two new phases СаСО₃·MgСО₃-dolomite (Ca∙Mg) and К₂CO₃·СаСО₃-(К∙Сa) are formed for this system at this temperature.

REVIEWER: Davlatshoeva J.A.,

Candidate of Chemical Sciences,

Associate Professor

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SOLUBILITY AND PHASE EQUILIBRIUM WATER-SALT SYSTEMS OF POTASSIUM, MAGNESIUM, CALCIUM CARBONATES FOR TEMPERATURE 25°C (K⁺,Mg²⁺,Ca²⁺//CO₃^2--H₂O)

The article presents the results of studying the solubility of the K⁺, Mg²⁺,Ca²⁺//CO₃^2--H₂O system at a temperature of 25°C using the translation method. It is very necessary to know the laws of the structure of the phase diagram in it for the processing of natural mineral substances and industrial waste containing salts of potassium, calcium and magnesium carbonates. One of the current environmental problems in our country is the presence of various wastes, including wastes from industrial enterprises, which have a negative impact on the environment. Therefore, studying the solvability of such systems is not only of theoretical importance, but also of great scientific and practical importance. The solubility of the K⁺,Mg²⁺,Ca²⁺//CO₃^2--H₂O system at a temperature of 25⁰C was studied experimentally, based on the obtained evidence, for the first time. It is shown in Figure 2. a) presented water-salt part, b) salt part.

Key words: phase equilibria, translation method, industrial waste, temperature 25^oC, curves, fields, pointsInformation about the authors:

Information about the authors: Umarali Safarali – Tajik State Pedagogical University named after Sadriddin Ayni, Senior lecturer of the Department of Chemical technology and ecology. Address: 734003, Dushanbe, Tajikistan, Rudaki Avenue, 121. Phone: (+992) 917861226. E-mail: safarali.umarali91.

Usmonov Muhammadsalim Bozorovich – Tajik State Pedagogical University named after Sadriddin Ayni, candidate of chemical sciences lecturer of the Department of Chemical technology and ecology. Address: 734003, Dushanbe, Tajikistan, Rudaki Avenue, 121. Phone: (+992) 918887812. E-mail: This email address is being protected from spambots. You need JavaScript enabled to view it..

Article received 19.02.2024

Approved after review 11.05.2024

Accepted for publication 30.08.2024

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SOLUBILITY AND PHASE EQUILIBRIUM OF AN WATER SYSTEM - POTASSIUM, MAGNESIUM, CALCIUM SALTS CARBONATES AT A TEMPERATURE OF 25°C