A team of researchers from the University of Texas at Austin and the State University of Iowa said they had managed to improve the technology of reverse osmosis – a method of desalination of seawater, known to mankind for more than 200 years. The scientists’ finding improved the technology’s efficiency by 30-40 percent.
Reverse osmosis is a water purification technology that uses semi-permeable membranes to separate unwanted molecules and ions from water. It is based on a natural process – osmosis. Its essence is the movement of water from a more saturated solution to a less saturated one through the membranes. Osmosis plays an important role in maintaining cell life.
In reverse osmosis, water is “pressed” through a membrane under pressure to remove organic and inorganic impurities, making it suitable for drinking. To improve the method has been actively worked over the past 40 years, as stocks of drinking water in the world is rapidly diminishing.
The main problem along the way is improving the semi-permeable membranes through which non-desalinated water passes. “Pushing” water through membranes requires a lot of energy, and scientists still don’t really know exactly how water passes through them and what happens to it there.
Now, thanks to the efforts of a group of researchers from the USA and two American water treatment companies – Dow Chemical Company and DuPont Water Solutions – we know a bit more about the properties of semi-permeable membranes used in reverse osmosis. In particular, the homogeneity of these membranes at the nanoscale plays an important role.
The idea behind the study was based on the observation that reverse osmosis technology was effective if the membranes were thicker. At first glance, this doesn’t seem logical, because water would pass through more material.
But colleagues at the University of Iowa in Texas created a 3D model of such a membrane on a supercomputer and simulated the movement of water through it. It turned out that the thickness of the membrane played almost no role in the speed of water passage – of greater importance was the homogeneity and the presence of cavities in it.
In other words, if the membrane is thick and homogeneous, more undetermined water can pass through it with less energy. Experimentally, the authors of the study were able to achieve 30-40% greater efficiency when using reverse osmosis.
Salt water (which is the oceans and seas) makes up about 97% of all water on Earth. According to the World Health Organization, more than 785 million people worldwide do not have access to clean drinking water. Because of global climate change, the number of such people will only increase. So, salt water is a huge untapped resource for drinking water, so scientists are looking for ways to purify the water.
“The management of drinking water resources is now an important challenge around the world. Water shortages, droughts – as weather conditions worsen, these problems are only expected to worsen. That’s why it’s important to have access to clean water supplies, particularly in areas where water is scarce,” says Enrique Gomez.