Electrochemical Desalination of Seawater and Hypersaline Brines with Coupled Electricity Storage

We present a zinc|ferricyanide hybrid flow battery that achieves extensive first-pass desalination while simultaneously supplying electrical energy (10 Wh/L). We demonstrate 85% salt removal from simulated seawater (35 g/L NaCl) and 86% from hypersaline brine (100 g/L NaCl), together with reversible battery operation over 100 h with high round-trip efficiency (84.8%). The system has a high operating voltage (E0 = +1.25 V), low specific energy consumption (2.11 Wh/L for 85% salt removal), and a desalination flux (4.7 mol/m2·h) on par with that of reverse osmosis membranes. Salt removal was similarly effective at higher feed salinities, for which reverse osmosis becomes physically impossible because of the pressure required. The results have positive implications for regions that rely on desalination for their freshwater needs, especially where sea salinity is high. Alternatively, the battery may also be useful in minimal liquid discharge wastewater treatment if operated as a brine concentrator.