This device is central to a new wastewater purification technique developed by researchers at the Beckman Institute for Advanced Science and Technology at the University of Illinois Urbana-Champaign. Credit: Beckman Institute for Advanced Science and Technology Communications Office
Key points:
- Modified electrodialysis method replaces water-splitting with an energy-efficient redox reaction
- The design allows for use of inexpensive nanofiltration membranes
- Researchers successfully applied the system to desalination and purification of wastewater
A new water purification method based on electrodialysis effectively removes salt and organic matter while cutting both costs and energy consumption. The method could improve access to clean drinking water in low resource areas.
The system designed at the Beckman Institute for Advanced Science and Technology reduces energy use by 90% compared to traditional electrodialysis. While desalination by electrodialysis typically requires an energy-intensive water-splitting reaction, the team’s novel method uses a more efficient reduction-oxidation (redox) reaction.
The system also lowers costs because it does not require ion-exchange membranes, which are expensive and require frequent replacement. Instead, the researchers used nanofiltration membranes that are more affordable and robust.
To remove the need for water-splitting, the team designed a special polymer-based material that is added to the water prior to purification. This material changes the charge of the entire water molecule instead of splitting the molecule into a positively-charged proton and negatively-charged hydroxide.
This change in charge via the redox reaction expends much less energy than water-splitting while achieving the same degree of salt separation. The team’s paper, published in ACS Energy Letters, describes how experiments at a water treatment plant demonstrated the method’s ability to successfully desalinate and purify wastewater.
“We need a way to purify drinking water that’s low-energy, inexpensive, and useful for the communities that need it the most,” said corresponding author Xiao Su, a Beckman researcher and assistant professor of chemical and biomolecular engineering at the University of Illinois Urbana-Champaign. “I see our solution as a platform to tackle both the energy and water crises.”
While the method has been tested using multiple liters of wastewater, the researchers hope to scale up the method to purify larger volumes of water, and also extend its application to salt water and brackish water.