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.
Desalination membranes remove salt and other chemicals from water, a critical process for society’s health, cleaning billions of gallons of water for agriculture, energy production and beverage. The idea seems simple – push salt water and clean water comes out the other side – but it contains complex complexities that scientists are still trying to understand.
The research team, in partnership with DuPont Water Solutions, solved an important aspect of this mystery, opening the door to reducing the costs of clean water production. The researchers found that desalination membranes are inconsistent in terms of density and mass distribution, which can impede their performance. Uniform nanomedical density 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 are still many things we don’t know,” said Manish Kumar, an associate professor in the Department of Civil, Architectural and Environmental Engineering at UT Austin. led the research. “I couldn’t really tell how the water was moving through them, so all the improvements over the last 40 years have been essentially in the dark.”
The findings were published today in Science.
The paper documents an increase in the efficiency of the tested membranes by 30% -40%, which means that they can clean more water while using significantly less energy. This could lead to increased access to clean water and lower water bills for both individual households and large users.
Reverse osmosis membranes work by applying pressure to the saline feed solution on one side. The minerals remain there as the water passes. Although it is more efficient than membrane-free desalination processes, it requires a large amount of energy, the researchers said, and improving the efficiency of membranes could reduce this burden.
“Managing freshwater is becoming a crucial challenge around the world,” said Enrique Gomez, a professor of chemical engineering at Penn State who led the research. “The lack of drought – with the increase in severe weather conditions, this problem is expected to become even more significant. It is extremely important to have clean water available, especially in low-resource areas.”
The National Science Foundation and DuPont, which make many desalination products, have funded the research. The seeds were planted when DuPont researchers found that the thicker membranes proved to be more permeable. This was a surprise, because conventional science has been that thickness reduces the amount of water that can flow through membranes.
The team connected with Dow Water Solutions, which is now part of DuPont, in 2015, at a “water summit” organized 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 nanomatic scale using state-of-the-art electron microscopes at the Penn State Materials Characterization Laboratory. They modeled the path that water takes through these membranes to predict how efficiently water can be cleaned based on the structure. Greg Foss of the Texas Advanced Computing Center helped visualize these simulations, and most of the calculations were performed on Stampede2, the TACC supercomputer.
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