Electrodialysis with asymmetrically profiled membranes: Influence of profiles geometry on desalination performance and limiting current phenomena

Abstract

Electrodialysis (ED) has recently gained much attention in the wide field of desalination and water treatment. However, energy consumption and capital costs may impair the process competitiveness. In this regard, limiting current density (LCD) and current efficiency (η) are key performance parameters for optimized ED systems. In this work, an experimental campaign was carried out characterizing the performance of ED stacks when adopting asymmetrically profiled membranes. Current–voltage curves were recorded under different operating conditions mimicking the operation of brackish water or seawater desalination units. Results showed that there was a preferable direction of the electric current relative to the membrane profiles, which provided higher values of LCD and of maximum η. Stacks with Overlapped Crossed Filaments profiled membranes performed better than conventional ED stacks with flat membranes and spacers by increasing the LCD (by ~20% under various operating conditions) and the maximum η (e.g., from ~55–65% to ~70–73% at 0.5 – 60 g/l inlet concentrations of diluate and brine, respectively). The specific energy consumption was significantly reduced (even more than 50%). On the contrary, the investigated pillar-profiled membranes exhibited the worst performances. The present results suggest that well-designed profiled membranes can reduce the costs of desalination via ED.