Producing clean water at a lower cost could be on the horizon after researchers at the University of Texas at Austin and Penn State solved a complex problem that has baffled scientists for decades, until now.
Desalination membranes remove salt and other chemicals from water, a process essential to the health of society, cleaning up billions of gallons of water for agriculture, energy production, and consumption. The idea sounds simple – push salt water through and clean water comes out the other side – but it contains complex intricacies that scientists are still trying to figure out.
The research team, in partnership with DuPont Water Solutions, solved an important aspect of this mystery, opening the door to reducing the costs of producing clean water. Researchers have determined that desalination membranes have inconsistent density and mass distribution, which can adversely affect their performance. Uniform density at the nanoscale is the key to increasing the amount of clean water these membranes can create.
“Reverse osmosis membranes are widely used to clean water, but there is still a lot we don’t know about them,” said Manish Kumar, associate professor in the Department of Civil, Architectural and Environmental Engineering. at UT Austin, who co-led the research. “We couldn’t really tell how the water was going through them, so all of the improvements over the past 40 years have basically been done in the dark.”
The results were published today in Science.
The paper documents an increase in efficiency of the membranes tested from 30% to 40%, which means they can clean more water while using much less energy. This could lead to better access to drinking water and lower water bills for single-family homes and heavy users.
Reverse osmosis membranes work by applying pressure to the salt feed solution on one side. The minerals stay there as the water passes. Although more efficient than membrane-less desalination processes, it still requires a large amount of energy, the researchers said, and improving membrane efficiency could reduce this load.
“Managing freshwater is becoming a crucial challenge around the world,” said Enrique Gomez, a chemical engineering professor at Penn State who co-led the research. “Shortages, droughts – as extreme weather conditions increase, this problem is expected to become even more serious. It is extremely important to have safe drinking water available, especially in areas with scarce resources. . ”
The National Science Foundation and DuPont, which manufactures many desalination products, funded the research. The seeds were planted when DuPont researchers found that thicker membranes were actually more permeable. This was a surprise as the conventional knowledge was that the thickness reduces the amount of water that can flow through the membranes.
The team connected with Dow Water Solutions, now part of DuPont, in 2015 at a “water summit” hosted by Kumar, and they were eager to solve this mystery. The research team, which also includes researchers from Iowa State University, developed 3D reconstructions of the membrane structure at the nanoscale using state-of-the-art electron microscopes in the lab. of Penn State Materials Characterization. They modeled the path water takes through these membranes to predict the efficiency of water cleaning based on structure. Greg Foss of the Texas Advanced Computing Center helped visualize these simulations, and most of the calculations were done on Stampede2, TACC’s supercomputer.
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