The energy-intensive nature of water desalination processes is being overcome with new electrochemical technologies that use capacitive or battery electrodes. A battery electrode deionization (BDI) technique devised at Pennsylvania State University eliminates the regeneration stage required in standard capacitive deionization (CDI) methods and lowers the voltage needed for process completion.

A typical CDI cell consists of two electrodes attached on opposite sides of a flow channel. Cations bind to the A feed solution contained in a reservoir was separately fed to the two inlets of the flow cell using pumps, one desalinated and the other concentrated. The conductivity of the discharge was then measured using flow conductivity meters located at each outlet, which were monitored by computer. Source: Taeyoung Kimcathode and anions bind to the anode, but high applied voltages greater than 1.2 V result in parasitic reactions and irreversible electrode oxidation.

By contrast, the newly developed BDI system uses a custom-built flow cell that uses two channels separated by a membrane, and two identical battery electrodes are secured at each end.

The system was tested by supplying each channel with a salty solution at a specified flow rate while applying a constant electrical current. Different current densities were used, depending on the number of membrane stacks, and the cell voltage flow was reversed when it reached a low of −0.6 V or a high of +0.6 V.

The set-up effectively removed salt at levels consistent with CDI with only an applied voltage of 0.6 V. The low voltage required and materials used helped prevent unwanted side reactions, achieved greater desalination abilities and consumed less energy than traditional CDI.

The simultaneous production of desalinated and concentrated water in two channels also eliminates the two-cycle approach, so the system no longer needs to rely on a regeneration stage. Stacking additional membranes between electrodes was observed to reduce energy consumption even further.

The current BDI version is not applicable to seawater and other very salty solutions, but it could be effective as a low energy method for brackish water, such as groundwater, or for desalinating water before it enters treatment plants.