Access to clean drinking water remains a major global challenge.
According to the United Nations, approximately 2.2 billion people lack safely managed drinking water.
Many regions, including parts of California and the Middle East, rely on desalination plants to convert seawater into fresh water.
Today’s desalination technologies have significant drawbacks. Most systems use large amounts of energy and often leave behind a very salt-rich waste known as brine.
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When this brine is released back into the ocean, it can harm marine ecosystems by increasing salinity levels and reducing the oxygen content of the water.
Now, researchers at the University of Rochester have developed a new solar-powered desalination technology that can provide a cleaner and more sustainable alternative. The system produces fresh water using sunlight, requires no chemical additives, and leaves no harmful brine.
The research team, led by Professor Chunlei Guo of the University of Rochester’s Institute of Optics, has described the technology in the journal Light: Science & Applications.
The system relies on special solar panels made of black metal that are etched with ultra-fast femtosecond lasers. This treatment creates a surface that absorbs almost all incoming sunlight while strongly attracting water.
When seawater comes into contact with the panel, a thin layer spreads over the surface. The absorbed solar energy heats and evaporates the water, leaving salts and minerals behind. Unlike conventional systems, the salt does not accumulate where evaporation occurs.
The researchers solved this problem by carefully designing microscopic grooves on the metal surface. These grooves direct the salts away from the active evaporation region to a separate region where they can be collected without interfering with the desalination process.
The design takes advantage of a well-known phenomenon called the “coffee ring effect”. When a drop of coffee dries on a table, the liquid evaporates while the coffee particles collect around the edge, leaving a dark ring. The researchers use the same principle to move salts towards the outer edges of the panel.
To test the technology, the team used seawater collected from the Pacific, Atlantic, and Indian Oceans. The system successfully produced fresh water while continuously diverting the salts away from the work surface, thus creating a self-cleaning desalination system.
One of the most important advantages is that the system captures almost all of the dissolved salts as solid materials instead of producing liquid brine. These recycled materials can become valuable resources. Ordinary table salt can be collected, and more valuable minerals can also be extracted.
In a related study, the researchers showed that the same technology can recover lithium, a key ingredient in rechargeable batteries. By adding special nanoparticles to the panel surface, they were able to separate lithium from other salts. Tests with water from Utah’s Great Salt Lake recovered about half of the lithium present.
The researchers believe the technology can be scaled up for larger applications. If successful, it could help provide clean drinking water to millions of people, while also recovering valuable minerals and reducing the environmental impact of desalination.
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