Water electro-transport with hydrated cations in electrodialysis

Electrodialysis (ED), an efficient, low energy consumption and environmentally friendly separation and desalination technology, has attracted great attentions. Due to a drawback in water transport mechanism from the dilute stream to the concentrate one, its applications are limited, especially on the concentrating or desalinating seawater/brackish water, biological products-contained streams. In this work, the relationship between water transport rate (WTR) and ion species in ED was firstly studied by using ion exchange membranes with different ion exchange capacities (IECs). A mathematical model based on Nernst-Planck equation was established to further associate WTR with IECs, membrane matrix backbone materials, bulk solution concentration, electrolyte type, etc. The results indicate that WTR during ED is a very significant phenomenon and cannot be ignored. To mitigate this effect, attention should be paid to the modification of membrane matrix materials and the selection of suitable IEC or functional groups or the introduction of ligands to obtain a win-win coupling of high desalination ability and low WTR.