A new solar-powered desalination technology converts seawater into drinking water while eliminating brine waste and extracting valuable minerals.
Billions of people worldwide still lack reliable access to safe drinking water. The United Nations estimates that around 2.2 billion people do not have safely managed drinking water services. To meet rising demand, regions like California and the Middle East use desalination plants to turn seawater into freshwater.
However, traditional desalination techniques like reverse osmosis and thermal distillation have major limitations. They require high energy input, often depend on chemical treatments before and after processing, and produce highly concentrated brine. When this waste is released into the ocean, it can harm marine ecosystems by raising salinity and lowering oxygen levels.
Researchers at the University of Rochester have introduced a new method that could overcome many of these issues. Their solar-powered system produces freshwater efficiently, removes liquid brine waste, and requires no chemical pretreatment.
The study was led by Chunlei Guo of the University of Rochester and published in Light: Science & Applications.
Solar Desalination Using Laser-Treated Metal
The system uses specialized solar panels made from black metal textured with ultrafast femtosecond lasers. This treatment gives the surface two key properties: strong solar absorption and high water affinity, known as superwicking.
A laser-structured active area spreads a thin film of seawater across the panel. The material absorbs almost all incoming sunlight, heating the water and triggering evaporation. During this process, salts and minerals are separated from the water and pushed toward untreated areas of the panel, referred to as the passive region.
By keeping salt away from the evaporation zone, the system avoids buildup that could disrupt continuous freshwater production.
Leveraging the Coffee Ring Effect to Prevent Blockages
Guo explains that several solar-thermal desalination methods have produced encouraging results in laboratory settings using simplified seawater made from water and sodium chloride.
In these experiments, sodium chloride forms porous, grain-like crystals as the water evaporates. These structures still allow water to pass through, enabling the salt to dissolve again and making the panels fairly easy to clean.
However, real seawater is much more complex.
Alongside sodium chloride, it contains many dissolved minerals. Compounds based on magnesium and calcium, for instance, tend to form dense, crust-like layers that obstruct water flow. Over time, such deposits can clog the desalination surfaces and significantly reduce the system’s effectiveness.
This effect is similar to what we see in everyday life, such as mineral buildup inside a showerhead or scale forming in a kettle—only seawater contains much higher levels of dissolved salts.
To address this issue, the Rochester researchers designed microscopic grooves on the black metal surface that guide salts and minerals away from key working areas, preventing buildup.
They also made use of a well-known physical phenomenon called the coffee ring effect. As Guo explains, “If you drop coffee on a surface, the water evaporates and leaves a ring of concentrated particles at the edge. We apply the same idea to move salts toward the passive region.”
When tested using seawater from the Pacific, Atlantic, and Indian Oceans, the system consistently produced freshwater while continuously pushing salts into the passive area. This self-cleaning action preserved efficiency and allowed the accumulated salts to be collected afterward without reducing performance.
Converting Salt Waste into Valuable Resources
One of the key benefits of this technology is that it eliminates the production of liquid brine.
Instead, most of the dissolved salts are recovered as solids. These recovered materials could potentially be used as table salt or processed further to extract more valuable elements.
A particularly important example is lithium, a crucial material for lithium-ion batteries found in electric vehicles and a wide range of electronic devices.
In a related study published in Journal of Materials Chemistry A, Guo and his team showed that the same superwicking solar panels can also assist in separating lithium from other salts during the desalination process.
The researchers incorporated hydrogen titanate nanoparticles into the microscopic grooves of the black metal surface. These particles are designed to selectively bind lithium while allowing other salts to pass through.
Guo explains that extracting lithium from terrestrial sources is highly energy-intensive and environmentally demanding, making recovery from saltwater a potentially important alternative in the future.
Using samples taken from Utah’s Great Salt Lake, the team was able to recover about 50 percent of the lithium contained in the salt mixture remaining after desalination.
A Possible Approach to Address Water and Mineral Supply Challenges
Although the technology has only been tested in small proof-of-concept devices so far, Guo believes it has the potential to be scaled up for larger use.
If successfully developed at scale, it could improve global access to clean drinking water while also providing a more sustainable way to obtain critical minerals like lithium.
Read the original article on: SciTechDaily
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