A research project conducted at the Center for Integrated Nanotechnologies found that by imitating Mother Nature, scientists at Sandia Labs were able to develop a new membrane to produce fresh water. By mimicking an algae protein, the membrane can remove salt from seawater and wastewater to produce fresh water for agriculture and power generation, while using less electricity than the current method. The project was funded by the research and development program led by the Sandia laboratory.
By adding a common amino acid, called phenylalanine, to an electrodialysis membrane, the researchers found that it allowed the membrane to better capture and remove positive ions, such as sodium. Susan Rempe, a bioengineer at Sandia National Laboratories, and Stephen Percival, a materials scientist, shared their membrane design in a recent article published in the peer-reviewed scientific journal. Soft matter.
Currently, electrodialysis using electrical energy is used to capture salt from seawater. This facilitates the removal of salt from brackish water to make fresh water and produce table salt. The new, more efficient membrane could also be used to remove salt from industrial wastewater to provide a new source of fresh water.
“The addition of phenylalanine to the electrodialysis membrane increased the selectivity for positive ions by a significant amount, to our pleasant surprise,” said Chief Bioengineer Rempe.
Ensuring an adequate supply of fresh water is a national security concern, Rempe added. Fresh water is essential for everything from consumption and agriculture to generating energy from nuclear power plants, coal and natural gas.
There are few options for cleaning up salty wastewater. The more concentrated the salt solution, the more difficult it is to remove the salt. The water produced by hydraulic fracturing to recover natural gas can be ten times saltier than sea water. As a result, the produced water is usually buried underground instead of being returned to the environment, said Rempe.
Due to its salty nature, while some oil and gas operators reuse water for power generation, the wastewater produced is often buried underground. The new membrane could be a way to economically desalinate industrial wastewater.
“Our partners at the University of Texas at El Paso analyzed our membrane in a real electrodialysis system,” Rempe added. “They placed membrane samples in their lab-scale system, performed numerous tests and compared our membrane to commercial membranes. Our membrane worked pretty well.
For a future research project, Rempe would like to design an electrodialysis membrane capable of separating specific ions of economic value, such as ions of rare earth metals. Rare earth metals are used in automotive catalytic converters, strong magnets, rechargeable batteries, and mobile phones, and are mainly mined in China.
“Rare earth metals are precious and the lack of domestic supply is a national security concern. Together, taking care of our water supply and recycling our precious minerals is important for environmental security and climate change mitigation. said Rempé.
Gwynne Ann Unruh is an award-winning journalist, formerly of the Alamosa Valley Courier, an independent newspaper in southern Colorado. She covers the environment for The Paper.