Fig. 4.

(A) Photograph of the recirculating FDI system incorporating inlet valves (IVs) and outlet valves (OVs) that direct fluid to/from electrodes from/to a brine reservoir (BR) and a diluate reservoir (DR). (B) Top view of the cell showing valve locations. Detailed views of (C) the inlet region of the cell showing PBA symmetric electrodes sandwiching an anion exchange membrane (AEM) and (D) of valve switching actions. The time sequence of cell voltage and salt concentration used to conduct one complete cycle is shown using inset diagrams together with the timing of valve and current switching events controlled automatically. PC, OC, and NC respectively denote positive current, open circuit, and negative current conditions.