Enhanced desalination performance of an electrodialysis stack in over-limiting current by adding AC/Fe3O4 nanocomposite as a flow electrode

Abstract

The primary aim of this study was to investigate the enhanced desalination performance of the electrodialysis (ED) stack under over-limiting current conditions. This was achieved by coupling the flow-electrode capacitive deionization (FCDI) process with the ED stack, incorporating an AC/Fe3O4 nanocomposite (NC) as a flow electrode in the electrode and concentrate compartments. The results obtained indicate that utilizing AC/Fe3O4 NC in the electrode compartment during the ED process, under a potential of 15 V, has led to a significant enhancement in desalination efficiency and current efficiency (CE). Specifically, the desalination efficiency and CE have increased from 60 % to 89.3 % and 35.9 % to 72 %, respectively, compared to the absence of AC/Fe3O4 NC. The desalination efficiency was increased to 93.24 % and the ASRR reached 1.46 μmol cm−2 min−1 by simultaneously adding AC/Fe3O4 NC to the electrode and concentrate compartments. This improvement can be attributed to a reduction in solution resistance, the electro-sorption of ions in the electrical double layer (EDL) of NC, as well as a decrease in ion concentration polarization. Moreover, it is likely that Fe3O4 nanoparticles of NC have resulted in electrical and membrane surface heterogeneity. These factors collectively contribute to the enhancement of the electroconvection phenomenon during the ED process.