Scientists managed to transform seawater into freshwater without generating harmful brine

Billions of people around the world still lack access to safe drinking water. In this context, desalination has become an increasingly used alternative by different regions that depend on seawater to obtain this resource. However, conventional methods present some drawbacks. Reverse osmosis and thermal distillation can require large amounts of energy and, in addition, generate a waste product known as brine: water with a very high concentration of salts and minerals. When this is returned to the ocean, it can increase local salinity and decrease oxygen levels, creating harmful conditions for marine organisms. Now, researchers at the University of Rochester in the United States have developed a solar desalination system that seeks to avoid this problem. The method was described in an article published in the journal Light: Science & Applications. The research was led by Chunlei Guo, professor of optics and physics at the University of Rochester. Scientists managed to transform seawater into fresh water without generating harmful brine. Photo: Pexels A panel that uses sunlight The technology uses panels of black metal treated with femtosecond lasers, extremely brief pulses of light that modify their surface. This allows the material to absorb much of the sunlight and allows the water to spread over it in a very thin layer. When receiving solar radiation, that layer of seawater heats up and evaporates. The water turns into vapor, but the salt and other minerals that were dissolved in it remain on the panel. To prevent these residues from accumulating in the evaporation zone, the researchers designed small grooves that move them toward the edges of the panel, where they can be collected. The system takes advantage of the so-called "coffee ring effect" for this. When a drop of coffee dries, the water evaporates, while its particles tend to concentrate at the edges. The researchers use a similar principle to carry the salts toward the ends of the panel, preventing them from forming a layer that could block its operation. Scientists managed to transform seawater into fresh water without generating harmful brine. Photo: Pexels Tested with water from three oceans One of the main challenges of solar desalination is avoiding the accumulation of minerals. The problem is especially complex when real seawater is used, which contains magnesium, calcium and other substances, in addition to sodium chloride. The researchers tested their system with seawater collected from the Pacific, Atlantic and Indian oceans. In the experiments, the salts were moved to the passive zone and could later be collected, without reducing the desalination efficiency. In this way, the system extracts almost 100% of the dissolved salts in solid form, instead of producing liquid brine.