Determination of critical parameters for the mathematical modelling of an electrodialysis process using a 3D-printed reactor

Measuring critical experimental parameters like electrical membrane resistance ( R m ), exchange current density (j 0 ) or the Tafel slope (b) in pilot or pre-pilot electrodialysis (ED) reactors can be challenging and often lead to imprecise outputs. These parameters can be precisely measured in smaller customed or commercial devices. However, if the hydrodynamics and characteristic features of the ED reactor are not correctly replicated, the calculated parameters may not be representative of the ED process, thus leading to wrong process modelling. In this context, 3D-printing emerges as a powerful tool capable of replicate, at a reduced scale, the hydrodynamics of larger reactors cost-effectively. The present study aims to 3D-print an electrodialyzer, characterize its performance both by CFD calculations and experimentally, and later measure those characteristic parameters ( R m , j o and b) and assess their influence on the mathematical modelling of an ED process, comparing it to non-calculated parameters. The case study selected has been a water desalination process. The results obtained show that the 3D-printing technology effectively reproduces the hydrodynamics of the pre-pilot reactor studied. The CFD calculations successfully predict the real hydrodynamic behavior in terms of fluid velocity, path, and residence time distribution (RTD). Subsequently, the R m , j 0 and b parameters, highly dependent on the experimental conditions, have been calculated and added to a standard initial mathematical model to reproduce and simulate electrodialysis experiments. Different experiments have been carried out varying the initial salt concentration, highly related to the initial conductivity, of the water samples. The determination coefficient (R 2 ) of 0.92 obtained using the calculated parameters is almost constant with the different starting conductivities of water and improved the results obtained with standard of tabulated parameters.