Identify key challenges

Identify the key challenges faced by industrial applications in electrolyte Thermodynamics

The diversity of the industrial partners collaborating within the EleTher JIP makes it possible to be as exhaustive as possible in the identification of the challenges (examples).

As was already pointed out during a round-table held during ESAT 2021 meeting, they strongly depend on the application:
  • sometimes (leaching or scale fomation applications) the solubility limit of salts in various types of solutions are needed
  • elsewhere (in stripping or distillation applications) the volatility of the molecular compounds is important
  • in some cases, the design of an extractive solvent requires the understanding of liquid-liquid equilibria
  • in corrosion or electrochemical applications, the activity of ionic species is of direct interest as they contribute in the reaction scheme
In all cases, modelling tools are needed in order to be able to design the most adequate process. There are today only a limited number of commercially available tools, and they are generally difficult to parameterize for novel applications.  The JIP focuses on fluid phase properties.
A number of case studies are defined that allow analyzing the true complexity observed in industrial applications, but that remain sufficiently simple to inspire research projects.

Case studies

In order to evaluate the full complexity of the systems of interest, it was decided to focus on quaternary systems, as illustrated below: The salt MX is a combination of an acid (HX) and a base (MOH), that both form ions when dissolved in a high dielectric constant (permittivity) medium as water:
 HX = H+ + X-      ;        MOH = M+ + OH-
It is planned to also investigate RedOx couples in order to be able to cover the full range of possible reactions (acid/base and Red/ox).

When a cosolvent is added, the permittivity of the medium decreases, and as a consequence, the relative strength of the acid and the base change. The quaternary system therefore becomes in fact a system with nine components. Changing the concentration of the acid or the base affects the pH of the system, while changing the concentration of the non-aqueous solvent affects the permittivity and thus the ionic strength. The modelling of such system is therefore particularly challenging.

As an example case, specific questions may come up in the corrosion context when a strong acid condenses close to a Fe surface.

Within EleTher, it is the objective to propose best practices for developing a modeling approach for such a system in view of computing speciation or phase equilibria.