Battery-like Electrodes Desalinate Brackish Water
S. Himmelstein | October 18, 2017Schematic of the desalination process. Source: University of Illinois
University of Illinois engineers have theorized that technology used in sodium-ion batteries may efficiently desalinate seawater: salt is extracted and confined in a chamber separate from purified water by application of sodium- and chloride ion-containing electrodes.
The researchers constructed and tested a battery-like device to confirm the utility of the proposed method. The electrodes incorporated into the system were composed of a chemical analog to the compound Prussian blue — the intense pigment used in ink for blueprints. This material, which contains redox-active nickel hexacyanoferrate nanoparticles, can remove sodium ions as well as potassium, calcium and magnesium from brackish water.
The Prussian blue analog traps positively charged ions like sodium within its crystal structure. While other materials can perform the same function, the new analog incurs a much lower cost.
“To make a technology like this be economically feasible, it needs to be cheap and, ideally, have some value-added benefit,” said mechanical science and engineering professor Kyle Smith. “By showing that our device works well with lower-salinity waters, the door for use with inland brackish waters and possibly industrial wastewater has opened.”
The amount of salt removal is sufficient to demonstrate their concept using brackish water, but additional research is needed to determine how salt removal from higher-salinity seawater and wastewater will impact energy efficiency.