FORMATION OF PRECURSORS OF OXIDE SYSTEMS BASED ON FE(II, III) AND BA(II) IN AQUEOUS SOLUTIONS
Rubrics: 2. CHEMICAL TECHNOLOGY
Authors:
1.
Kazan National Research Technological University
2.
KNITU; KNRTU
3.
KNITU
4.
Kazan National Research Technological University
Kazan, Russian Federation
Kazan, Russian Federation
Type:
Article
Pages:
from 112
to 119
Status:
Published
Received:
23.12.2025
Accepted:
23.12.2025
Published:
23.12.2025
Language:
Russian
Keywords:
HETEROPHASE EQUILIBRIA, FE (II, III)-BA (II)-H2O-OH SYSTEM, COMPLEX FORMATION, POLYNUCLEAR COMPLEXES, MODELING
Abstract (English):
This paper demonstrates the possibility of predicting the composition of precursors of complex oxides or oxide systems using a potentiometric method based on measuring the pH of aqueous solutions of FeCl2 and FeCl3 over a wide range of values. Titration curves are presented, as well as experimental and calculated dependencies of the FeCl3-H2O-OH- system at a FeCl3 concentration of 0.00005-1.0 mol/L and the FeCl2-H2O-OH- system at a FeCl2 concentration of 0.1 mol/L. In all cases, the experimental curve agrees well with the calculated dependence. Potentiometric titration curves in the coordinates n = f(pH) are qualitatively described by a step with a beginning and a plateau, the number of steps observed during the transition from one solid phase to another, and the final part of the curve. On the calculated curve α = f(pH), small and larger sections of the line can be observed, with the former characterizing the pH of the region of compound formation in solution and the latter characterizing the solid phases. There is a significant difference between the values obtained in this study and the values of the constants given in the reference literature. This can be explained by both the different experimental conditions and the kinetic inertness of the reactions of polyatomic metal complex formation. It should be noted that the ambiguous description of complex formation in metal ion solutions is also due to the fact that most studies do not include the formation of poly-nuclear hydroxo complexes, and the description and explanation of the experiment is carried out taking into account the simplest set of mono-nuclear forms. As a rule, in such cases, when studying equilibria, despite the use of a complex set of informative methods, the system is presented with a narrow range of concentrations of basic components. The calculated curves obtained in this study are in good agreement with the experimental results. As a result, taking into account the wide range of concentrations, a mathematical model of heterogeneous systems Fe(II)-H2O-OH-, Fe(III)-H2O-OH-, and Ba(II)-H2O-OH- has been created.
This paper demonstrates the possibility of predicting the composition of precursors of complex oxides or oxide systems using a potentiometric method based on measuring the pH of aqueous solutions of FeCl2 and FeCl3 over a wide range of values. Titration curves are presented, as well as experimental and calculated dependencies of the FeCl3-H2O-OH- system at a FeCl3 concentration of 0.00005-1.0 mol/L and the FeCl2-H2O-OH- system at a FeCl2 concentration of 0.1 mol/L. In all cases, the experimental curve agrees well with the calculated dependence. Potentiometric titration curves in the coordinates n = f(pH) are qualitatively described by a step with a beginning and a plateau, the number of steps observed during the transition from one solid phase to another, and the final part of the curve. On the calculated curve α = f(pH), small and larger sections of the line can be observed, with the former characterizing the pH of the region of compound formation in solution and the latter characterizing the solid phases. There is a significant difference between the values obtained in this study and the values of the constants given in the reference literature. This can be explained by both the different experimental conditions and the kinetic inertness of the reactions of polyatomic metal complex formation. It should be noted that the ambiguous description of complex formation in metal ion solutions is also due to the fact that most studies do not include the formation of poly-nuclear hydroxo complexes, and the description and explanation of the experiment is carried out taking into account the simplest set of mono-nuclear forms. As a rule, in such cases, when studying equilibria, despite the use of a complex set of informative methods, the system is presented with a narrow range of concentrations of basic components. The calculated curves obtained in this study are in good agreement with the experimental results. As a result, taking into account the wide range of concentrations, a mathematical model of heterogeneous systems Fe(II)-H2O-OH-, Fe(III)-H2O-OH-, and Ba(II)-H2O-OH- has been created.
Keywords:
HETEROPHASE EQUILIBRIA, FE (II, III)-BA (II)-H2O-OH SYSTEM, COMPLEX FORMATION, POLYNUCLEAR COMPLEXES, MODELING
HETEROPHASE EQUILIBRIA, FE (II, III)-BA (II)-H2O-OH SYSTEM, COMPLEX FORMATION, POLYNUCLEAR COMPLEXES, MODELING
