In this work package, we will investigate the gasification of the loaded FCDI electrode material.

Our char has experienced a lot during the desalination tests. As a flow-electrode, it was immersed in an aqueous solution and charged during the FCDI process. Thus, aside from the water-washing effect, Faradaic reactions that accompany the deionisation process resulted in the change of the pH of the electrode solution and, in some cases, in mild char oxidation.

All these phenomena have affected the char, changing its surface chemistry and inherent inorganics composition. Now, it’s time to assess how the transformation of the char during the Na⁺ or Cl^– loading affected its gasification.

Our char (a) is full of inherent inorganics (b) that are affected during the FCDI process

In WP3, we will study the kinetics of char gasification using thermogravimetric analysis. This technique allows for continuous measurement of the weight of the sample during its thermal decomposition. The first derivative (DTG) of the registered mass loss curve is the indication of the reactivity of the material. Collecting DTGs under different process parameters, for example, in isothermal conditions at different temperatures or non-isothermal conditions with various heating rates, allows calculating the kinetic constants of the gasification process.

We will begin WP3 with preliminary studies to identify the most suitable gasification conditions and the most appropriate kinetic analysis method, e.g. isoconversional or model-based methods. Isoconversional methods assume that the reaction rate at a certain conversion level depends only on the temperature and can be described by one kinetic equation, as a single-step reaction process. Meanwhile, model-based methods use more complex mathematical calculations. WP3 leader, Paulina Wienchol, will use Kinetics NEO software to optimise the methodology for our kinetic analysis.

Once we determine the details of the methodology, we will compare the kinetic parameters of the pristine and spent chars to evaluate how the deionisation process affected our samples.