Periodic Reporting for period 3 - ElectroThermo (New Paradigm in Electrolyte Thermodynamics)
Reporting period: 2022-09-01 to 2024-02-29
The project’s overall target is to arrive at a fundamental understanding of electrolyte thermodynamics and thus enable the engineering of a new generation of useful, physically sound models for electrolyte solutions. These models should be general and applicable to a very wide range of conditions so that they can be potentially used for a wide range of applications. The aim is both to achieve a fundamental understanding of electrolyte thermodynamics but also to ensure contact with stakeholders (industry, etc) where electrolyte thermodynamics is expected to be relevant and useful.
Electrolyte solutions are present almost anywhere and find numerous applications in physical sciences including chemistry, geology, material science, medicine, biochemistry and physiology as well as in many engineering fields especially chemical & biochemical, electrical and petroleum engineering. In all these applications thermodynamics plays a crucial role over wide ranges of temperature, pressure and composition. As the subject is important, a relatively large body of knowledge has been accumulated with lots of data and models. However, disappointingly the state-of-the-art thermodynamic models used today in engineering practice are semi-empirical and require numerous experimental data. They lack generality and have not enhanced our understanding of electrolyte thermodynamics. Going beyond the current state of the art, we will create the scientific foundation for studying, at their extremes, both “primitive” and “non-primitive” approaches for electrolyte solutions and identify strengths and limitations.
The ambition is to make new advances to clarify major questions and misunderstandings in electrolyte thermodynamics, some remaining for over 100 years, which currently prevent real progress from being made, and create a new paradigm that will ultimately pave the way for the development of new engineering models for electrolyte solutions. This is a risky, ambitious and crucial task, but successful completion will have significant benefits in many industrial sectors as well as in environmental studies and biotechnology.
Electrolyte solutions are present almost anywhere and find numerous applications in physical sciences including chemistry, geology, material science, medicine, biochemistry and physiology as well as in many engineering fields especially chemical & biochemical, electrical and petroleum engineering. In all these applications thermodynamics plays a crucial role over wide ranges of temperature, pressure and composition. As the subject is important, a relatively large body of knowledge has been accumulated with lots of data and models. However, disappointingly the state-of-the-art thermodynamic models used today in engineering practice are semi-empirical and require numerous experimental data. They lack generality and have not enhanced our understanding of electrolyte thermodynamics. Going beyond the current state of the art, we will create the scientific foundation for studying, at their extremes, both “primitive” and “non-primitive” approaches for electrolyte solutions and identify strengths and limitations.
The ambition is to make new advances to clarify major questions and misunderstandings in electrolyte thermodynamics, some remaining for over 100 years, which currently prevent real progress from being made, and create a new paradigm that will ultimately pave the way for the development of new engineering models for electrolyte solutions. This is a risky, ambitious and crucial task, but successful completion will have significant benefits in many industrial sectors as well as in environmental studies and biotechnology.
The work performed so far includes molecular simulation and theoretical studies (at a fundamental level) and the development and comparison of electrolyte equations of state (at an applied engineering level).
Individual ion activity coefficients for water-salts have been obtained using molecular simulations and have confirmed at least qualitatively the rather controversial experimental data. Molecular simulation studies have also been carried out for pure water with emphasis on the study of hydrogen bonding. These studies appear to be in agreement with the two-state theory for water when the concept of “strong hydrogen bonds” is used.
Two electrolyte equations of state have been considered so far (e-CPA and e-SAFT-VR Mie) and applied in a wide range of electrolyte solutions. The performance of the models for individual ion activity coefficients, the analysis of the terms of the models as well the effect of using concentration dependency for the dielectric constant have been investigated. All these studies continue. Extensive databases for certain categories of systems (mixed solvents and gas solubilities) have also been compiled. From the so far studies, it appears that the Debye-Hückel theory in its complete form has very positive features as applied to electrolyte solutions, while the nature of the “physical” term of the thermodynamic models may be less crucial. The study on the importance of ion-water solvation (Born term) is not as yet concluded.
Finally, a wide range of models has been compared for the electrical conductivity and the possible importance of ion pairs has been illustrated.
At the dissemination level, in addition to publications/conferences, workshops on electrolyte thermodynamics have been organized as well as an extensive survey on industrial needs for thermodynamic properties which revealed the need for much better electrolyte models and understanding. Both of these studies have been carried out under the auspices of the European Federation of Chemical Engineering.
Individual ion activity coefficients for water-salts have been obtained using molecular simulations and have confirmed at least qualitatively the rather controversial experimental data. Molecular simulation studies have also been carried out for pure water with emphasis on the study of hydrogen bonding. These studies appear to be in agreement with the two-state theory for water when the concept of “strong hydrogen bonds” is used.
Two electrolyte equations of state have been considered so far (e-CPA and e-SAFT-VR Mie) and applied in a wide range of electrolyte solutions. The performance of the models for individual ion activity coefficients, the analysis of the terms of the models as well the effect of using concentration dependency for the dielectric constant have been investigated. All these studies continue. Extensive databases for certain categories of systems (mixed solvents and gas solubilities) have also been compiled. From the so far studies, it appears that the Debye-Hückel theory in its complete form has very positive features as applied to electrolyte solutions, while the nature of the “physical” term of the thermodynamic models may be less crucial. The study on the importance of ion-water solvation (Born term) is not as yet concluded.
Finally, a wide range of models has been compared for the electrical conductivity and the possible importance of ion pairs has been illustrated.
At the dissemination level, in addition to publications/conferences, workshops on electrolyte thermodynamics have been organized as well as an extensive survey on industrial needs for thermodynamic properties which revealed the need for much better electrolyte models and understanding. Both of these studies have been carried out under the auspices of the European Federation of Chemical Engineering.
Significant developments beyond the current state of the art are the molecular simulation studies (both individual ion activity coefficients for water-salts and hydrogen bonding of water), the coupling of molecular simulation and thermodynamic models in describing thermodynamic properties of water and investigation of the extent of hydrogen bonding incl. cluster formation, the systematic development of an electrolyte equation of state for gas solubilities but also the study of the extent thermodynamic models can represent a wide range of electrolyte properties, the systematic study of the concentration dependency of the dielectric constant in the context of the equation of state framework and the electrical conductivity studies for a very wide range of systems and conditions.
Expected results during the second phase of the project include the improvement of thermodynamic models for aqueous solutions, an in-depth theoretical study of the fundamentals of electrolyte thermodynamics and derivation of models for electrolyte solutions, the systematic studies and importance of ion-pairing in electrolytes, the development of critical ways to validate electrolyte data, the development of algorithms for testing models for mixed solvents-salts and the evaluation of thermodynamic model at this frontier of electrolyte thermodynamics, the comparison of primitive and non-primitive approaches for electrolytes as well as a systematic study of the ion-solvation phenomena. Solid-liquid equilibria and methods to predict standard properties as well as the investigation of AI/ML for electrolyte mixtures with biomolecules will also be studied.
It is also intended to proceed with more systematic dissemination of the results, beyond the scientific ones, to key stakeholders in the industry and academia.
Expected results during the second phase of the project include the improvement of thermodynamic models for aqueous solutions, an in-depth theoretical study of the fundamentals of electrolyte thermodynamics and derivation of models for electrolyte solutions, the systematic studies and importance of ion-pairing in electrolytes, the development of critical ways to validate electrolyte data, the development of algorithms for testing models for mixed solvents-salts and the evaluation of thermodynamic model at this frontier of electrolyte thermodynamics, the comparison of primitive and non-primitive approaches for electrolytes as well as a systematic study of the ion-solvation phenomena. Solid-liquid equilibria and methods to predict standard properties as well as the investigation of AI/ML for electrolyte mixtures with biomolecules will also be studied.
It is also intended to proceed with more systematic dissemination of the results, beyond the scientific ones, to key stakeholders in the industry and academia.