A comprehensive investigation of performance of pulsed electrodialysis for desalination of brackish water

Abstract

Pulsing the electric field is an operational strategy for suppressing concentration polarization (CP) in electrodialysis (ED). In this study, the effects of pulsing parameters on the desalination performance of ED were investigated. Experimental analyses were performed at sub-limiting and limiting regimes for frequencies of 0.5–100 Hz and duty cycles of 20–80 %. A 1-D transient model was developed to calculate the concentration profiles inside the cell. The results indicated that under the same input voltage, the cycle-averaged current density of the pulsed ED (PED) increased at higher frequencies and duty cycles while always remaining below the current density of conventional ED (CED). The energy savings gained from suppressing CP compensated for the inefficiencies introduced due to the longer desalination time, resulting in approximately similar specific energy consumption (SEC) compared to CED. Pulsed operation increased the limiting voltage, allowing for higher input voltages without intensifying water dissociation. However, increasing the pulsing voltage led to a higher SEC and reduced the effectiveness of the approach for suppressing CP. To enhance the viability of PED, pulsing parameters should be tuned according to the desalination objectives. This study provides the required insights for developing a generalizable optimization approach for PED.