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1

The influence of activity coefficient and equilibrium constant models on the speciation of aqueous solutions of H2SO4–MgSO4–Al2(SO4)3 at 235 and 250 °C

Dickson Okechukwu Vincent, Deleau Thomas, Coquelet Christophe, Espitalier Fabienne, Lombart Julien, Tardy Antoine

Physicochemical Problems of Mineral Processing

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2023

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Vol. 59, iss. 5

art. no. 167497

EN

Supersaturation occurs in many industrial applications promoting reactive crystallisation between the reactants to form solutes. These solutes accumulate during precipitation, leading to the formation of scales on the inner walls of the reactor and particularly around the stirrer, causing modifications in the hydrodynamics. This encrustation is responsible for process shutdowns in continuous crystallisation processes. Supersaturation control is essential for industrial processes aimed at controlling or inhibiting the formation of these solids. Knowledge of mineral solubility and chemical speciation is required to account for the composition of the complexes in the system in their various solid or aqueous forms. This speciation is obtained by considering the thermodynamic equilibrium constants of the dissociation/complexation reactions involved in the system, the pressure, and the activity coefficients of the chemical species in their molecular or electrolyte form. From these thermodynamic quantities and the state of the system, we can predict the direction of the reaction. This study highlights the risk of the lack of experimental information on equilibrium constants at high temperatures and moderate pressures. Our goal is to evaluate the accuracy of existing models classically used to predict the equilibrium constant in such very hard conditions encountered in hydrometallurgical processes. Furthermore, we demonstrate the influences of equilibrium constants estimation and activity coefficient models on the speciation of H2SO4–Al2(SO4)3–MgSO4 systems, forming hydronium alunite and kieserite in the laterite liquor of hydrometallurgical processes.

2

Remediation of CO2 in Boudouard’s reaction as an example of reversible chemical reaction

Szostak Elżbieta, Odrowąż Ewa, Górska Natalia

Chemistry-Didactics-Ecology-Metrology

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2020

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R. 25, NR 1-2

101--111

EN

One of the fundamental elements of a scientist's work is the ability to lead observations of the phenomena that surround us and based on them making conclusions. These observations are conducted within the so-called scientific experiments. Lessons learned based on the results obtained in experiments allow researchers to better understand the essence of the phenomena occurring in the world around us. Drawing conclusions is not always easy. In order to achieve this skill, we must possess a well-established knowledge in the field of the phenomenon that interests us. The most striking example of how important skills are observation and drawing proper conclusions is the phenomenon of global climate warming. The main parameter influencing temperatures registered on Earth is the concentration of greenhouse gases in the atmosphere, and especially carbon dioxide created from combustion processes. A significant role in studies of the reduction of CO2 emissions plays chemists. To be sure that conducted by them experiments are optimally designed, it is necessary to ensure them with proper education already at the secondary school level. The main aim of this article was to conduct the study in order to explain chemical issues that create the greatest cognitive difficulties among students. The second aim of the article was to propose a chemical experiment to students that would allow them to find out more about the phenomena governing in the area of problematic issues. The proposed experiment is based on the concept of solubility equilibrium. Results of preliminary tests that have been carried out after applying this experiment on a small group of students, indicated their better understanding of the studied subject.

3

Learners’ understanding of chemical equilibrium at submicroscopic, macroscopic and symbolic levels

Prokša M., Drozdíková A., Haláková Z.

Chemistry-Didactics-Ecology-Metrology

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2018

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R. 23, NR 1-2

97--111

EN

It is not easy for secondary school learners to comprehend the concept of chemical equilibrium at the level of understanding. In this context, a feedback is important for the teachers to optimize their help to students in constructing this concept. We designed and tested sets of particularly prepared tasks, the solution of which reflects the depth of understanding of the basic concept in macroscopic, submicroscopic and symbolic representation. Difficulties in understanding the chemical phenomena and concepts do not result only from the existence of these three levels or from their explanation using abstract concepts, but also from the lack of interconnection between these representations. Consistent interconnection of these levels can lead to an internal conflict in students, and consequently to a more profound understanding of the concept or relationships between concepts at multiple levels of representation to understand them or to change the meaning of one to another. There is also a close connection with the aspect of memory, algorithmic and conceptual approaches to solving educational situations, which extends dimensionally and reinforces the need for a more comprehensive grasp of learners’ mastery of the given concept. The teacher cannot expect that the learners without intensive training, e.g., only by observing the macroscopic representation, can interpret the essence of the submicroscopic representation. Therefore, these aspects need to be consistently involved in the model of learners’ cognitive process early enough to apply them in the educational practice without any problems.

PL

Uczniom szkół średnich nie jest łatwo zrozumieć pojęcie równowagi chemicznej. W tym kontekście ważna jest informacja zwrotna dla nauczycieli, aby zoptymalizować ich pomoc dla uczniów w konstruowaniu tej koncepcji. Zaprojektowano i przetestowano zestawy specjalnie przygotowanych zadań, których rozwiązanie odzwierciedla głębokość rozumienia podstawowej koncepcji w reprezentacji makroskopowej, submikroskopowej i symbolicznej. Trudności w zrozumieniu zjawisk chemicznych i pojęć nie wynikają jedynie z istnienia tych trzech poziomów lub z ich wyjaśnienia za pomocą abstrakcyjnych pojęć, ale także z braku wzajemnego połączenia między tymi reprezentacjami. Odpowiednie wzajemne połączenie tych poziomów może prowadzić do wewnętrznego konfliktu w umysłach uczniów, a w konsekwencji do głębszego zrozumienia koncepcji lub relacji między pojęciami na wielu poziomach reprezentacji, aby je zrozumieć lub zmienić ich znaczenia. Istnieje również ścisły związek z aspektem pamięci, algorytmicznym i koncepcyjnym podejściem do rozwiązywania sytuacji edukacyjnych, który rozszerza się wymiarowo i wzmacnia potrzebę bardziej wszechstronnego opanowania przez ucznia danej koncepcji. Nauczyciel nie może oczekiwać, że uczący się bez intensywnego treningu, np. tylko obserwując makroskopową reprezentację, mogą interpretować istotę submikroskopowej reprezentacji. Dlatego te aspekty muszą być konsekwentnie włączane w model procesu poznawczego ucznia wystarczająco wcześnie, aby zastosować je w praktyce edukacyjnej bez żadnych problemów.

4

Thermodynamic study to evaluate the selectivity behaviour of nuclear grade resin Indion-223 towards some univalent ions

Singare P. U., Mohammed A. L. K., Dixit N. N.

International Letters of Chemistry, Physics and Astronomy

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2014

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Vol. 15

22--29

EN

The present paper deals with the application of thermodynamic concept in understanding the preferential selectivity of nuclear grade anion exchange resin Indion-223 in H+ form towards Na+ and K+ ions in the solution. In the study it was observed that the equilibrium constants K values for H+/Na+ and H+/K+ uni-univalet ion exchange reactions increases from 0.01389 to 0.01855 and from 0.01710 to 0.02374 respectively as the temperature increases from 35.0 °C to 45.0 °C. The increase in K values with rise in temperature suggests endothermic ion exchange reactions having the enthalpy change values of 25.55 and 22.72 kJ/ mol respectively. Based on difference in K values and enthalpy values for the two uni-univalent ion exchange reactions, the preferential selectivity of the resin for the univalent ions in the solution was predicted. From the results of present study, it appears that the experimental technique used here can be applied further to understand the ionic selectivity of different industrial grade ion exchange resins. It is expected that such studies will provide valuable information in order to decide about the selection of those resins for efficient separation of various ionic species present in the industrial waste water effluents.

5

Study on preferential selectivity of nuclear grade resin Indion-223 towards some bivalent ions

Singare P. U., Mohammed A. L. K., Dixit N. N.

International Letters of Chemistry, Physics and Astronomy

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2014

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Vol. 15

11--21

EN

In the present paper attempts are made to understand the selectivity of nuclear grade cation exchange resin Indion-223 in H+ form towards Ca2+ and Mg2+ bivalent ions in the solution based on thermodynamic concept. It was observed that with rise in temperature the equilibrium constant K values for H+/Ca2+ uni-bivalet ion exchange reactions increases from 0.000397 to 0.000639. Similarly for H+/Mg2+ uni-bivalet ion exchange reactions the equilibrium constant K values increases from 0.000177 to 0.000333. The increase in equilibrium constant values with rise in temperature indicate endothermic ion exchange reactions having the enthalpy change values of 38.92 and 51.46 kJ/ mol respectively. The difference in K values and enthalpy values were used to predict the selectivity behaviour of the resin towards the Ca2+ and Mg2+ bivalent ions in the solution. The thermodynamic concept of the present study can be applied to understand the selectivity behaviour of different nuclear as well as non-nuclear grade resins towards wide range of ionic species present in the exchanging liquid medium.

6

Study on Halide Ions Selectivity of Nuclear Grade Anion Exchange Resin Auchlite ARA-9366

Singare P. U., Patange A. N.

International Letters of Chemistry, Physics and Astronomy

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2014

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Vol. 11, iss. 1

67-73

EN

The selectivity behaviour of nuclear grade anion exchange resin Auchlite ARA-9366 in chloride form towards iodide and bromide ions in the solution was studied. The trend in selectivity of the resin was predicted on the basis of thermodynamics of Clˉ/Iˉ and Clˉ/Brˉ uni-univalent ion exchange reactions. It was observed that the equilibrium constants K values for Clˉ/Iˉ ion exchange reaction were higher than that calculated for Clˉ/Brˉ exchange under identical experimental conditions. Also the enthalpy values for the two uni-univalent ion exchange reactions were calculated as -47.87 and -36.14 kJ/mol respectively. The high K and low enthalpy values obtained for Clˉ/Iˉ ion exchange reaction as compared to that obtained during Clˉ/Brˉ exchange supports higher selectivity of the resin towards iodide ions as compared to that towards bromide ions, when both the ions are present in the same solution.

7

Study on Halide Ions Selectivity of Industrial Grade Anion Exchange Resin Auchlite A-378

Singare P. U., Patange A. N.

International Letters of Chemistry, Physics and Astronomy

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2014

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Vol. 11, iss. 1

44-50

EN

The thermodynamic approach was applied to predict the trend selectivity of industrial grade anion exchange resin Auchlite A-378 in chloride form towards iodide and bromide ions in the solution. The study was conducted by performing the Clˉ/Iˉ and Clˉ/Brˉ uni-univalent ion exchange reactions under gradually increasing temperature conditions. The thermodynamic equilibrium constants K values were used to calculate the enthalpies of the two uni-univalent ion exchange reactions. It was observed that the K values for Clˉ/Iˉ ion exchange reaction were higher than Clˉ/Brˉ exchange reaction under identical experimental conditions. Also the enthalpy values for the two uni-univalent ion exchange reactions were calculated as -39.51 and -18.38 kJ/mol respectively. The high K and low enthalpy values obtained for Clˉ/Iˉ ion exchange reaction is responsible for higher selectivity of the resin towards iodide ions as compared to that towards bromide ions, when both the ions are present in the same solution.

8

Study of uni-univalent H+/K+ and uni-bivalent H+/Mg2+ ion exchange reactions using nuclear grade resin Indion-223

Singare P. U., Mohammed A. K. L., Dixit N. N.

International Letters of Chemistry, Physics and Astronomy

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2014

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Vol. 14, iss. 2

231-239

EN

In the present paper the uni-univalent and uni-bivalent ion exchange reactions were investigated using nuclear grade anion exchange resin Indion-223 in H+ form. For both H+/K+ uni-univalet ion exchange reactions and H+/Mg2+ uni-bivalet ion exchange reactions, the equilibrium constant K values increases from 0.01710 to 0.02374 and from 0.000177 to 0.000333 respectively as the reaction temperature rises from 35.0 °C to 45.0 °C. The increase in K values with temperature suggest endothermic ion exchange reactions having the enthalpy change values of 22.72 and 51.46 kJ/ mol respectively. The results of such studies will help in selection of suitable ion exchange resins in order to bring about efficient separation of different ionic species present in the waste water effluents released from nuclear as well as chemical process industries.

9

Comparative study of uni-univalent H⁺/Na⁺ and uni-bivalent H⁺/Ca²⁺ ion exchange reactions using nuclear grade resin Indion-223

Singare P. U., Mohammed A. L. K., Dixit N. N.

International Letters of Chemistry, Physics and Astronomy

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2014

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Vol. 14, iss. 2

127-135

EN

The present paper deals with the ion exchange equilibrium studies of uni-univalent and uni-bivalent ion exchange reactions using nuclear grade anion exchange resin Indion-223 in H⁺ form towards Na⁺ and Ca²⁺ ions in the solution. It was observed that with rise in temperature the equilibrium constants K values for H⁺/Na⁺ uni-univalet ion exchange reaction increases from 0.01389 to 0.01855. Similarly for H⁺/Ca²⁺ uni-bivalet ion exchange reaction the equilibrium constants K values increases from 0.000397 to 0.000639. The increase in equilibrium constant values with rise in temperature indicate endothermic ion exchange reactions having the enthalpy change values of 25.55 and 38.92 kJ/ mol respectively.

10

A determination of equilibrium constants for syntheses of methyl-tert-butyl and ethyl-tert-butyl ethers on sulfonic copolymer by gas chromatography

Słomkiewicz P.M.

Polish Journal of Chemical Technology

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2006

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Vol. 8, nr 2

97-101

EN

A method of determining equilibrium constants of catalytic reactions was described using gas chromatography. Both the equilibrium constants and enthalpies of methyl-tert-butyl ether from methanol and isobutene, ethyl-tert-butyl ether from ethanol and isobutene on catalyst Amberlyst 15 in the gas phase were determined. The enthalpy values of these reactions were compared with the enthalpies calculated from thermodynamic data and the experimental data given in the literature.