New Solar-Powered Desalination Method Produces Drinking Water and Extracts Lithium
Researchers at the University of Rochester developed a solar-powered desalination method that produces drinking water from seawater without chemical additives. According to a paper in Light: Science & Applications, the system uses laser-etched black metal to eliminate brine waste and can extract lithium for rechargeable batteries.
How does the solar-thermal desalination process work?
The technology relies on solar panels made of black metal etched with femtosecond lasers. This process creates a surface that is both super light-absorbing and “superwicking,” meaning it is extremely attractive to water, according to Chunlei Guo, a professor of optics and physics at the University of Rochester.
A laser-treated active region pulls a thin layer of water across the surface and absorbs nearly all solar radiation. This distills the water and pushes leftover salts and minerals into untreated “passive” regions.
Guo explains that the team used the “coffee ring effect” to keep the system running. This is the same principle that leaves a concentrated ring of particles when a coffee drop evaporates. By leveraging this, the system advances salts to the passive region, preventing the surface from clogging.
Why is this method better than traditional desalination?
Common techniques like reverse osmosis and thermal distillation are energy-intensive and require chemical pre- and post-treatment. These methods produce a concentrated saltwater byproduct called brine, which the University of Rochester reports can lower oxygen levels and raise salt levels in the ocean, harming sea life.
The new solar-thermal process requires no chemical additives and produces no brine. Instead, it extracts nearly 100% of the salts in solid form. This allows for the collection of table salt and other precious minerals without dumping waste back into the sea.
How can this technology provide minerals like lithium?
In a separate paper published in the Journal of Materials Chemistry A, Guo and his colleagues demonstrated the ability to isolate lithium from other salts. They achieved this by embedding hydrogen titanate nanoparticles in the grooves of the black metal surface.
Testing with water samples from the Great Salt Lake allowed researchers to extract approximately 50% of the lithium from the remaining salts. Guo states that pulling lithium directly from saltwater could be an important future route, as terrestrial mining is taxing on the environment and energy supplies.
What happens next for the technology?
The researchers have demonstrated these proofs of concept on small-scale devices. Because the technology is inherently scalable, it may be used to improve global access to drinking water.
Future applications could include the development of more sustainable supply chains for precious minerals. The research was supported by the National Science Foundation, the Bill & Melinda Gates Foundation, and the Worldwide Universities Network.
Frequently Asked Questions
What is the “coffee ring effect” in this process?
It is a physical phenomenon where evaporating liquid leaves a concentrated ring of particles at the outer edge. The researchers used this principle to move salts away from the active region of the solar panel to prevent clogging.
How does this system handle the complex composition of real ocean water?
Unlike simulated seawater, real ocean water contains magnesium- and calcium-based materials that typically form crusty, non-porous clogs. The team precisely etched the black metal’s grooves so these minerals would slough off, making the surface self-cleaning.
Which oceans were used to test the desalination technique?
The team tested the system using water samples from the Pacific, Atlantic, and Indian Oceans.
Do you think mineral recovery from seawater could replace traditional mining for battery materials?