World News – AU – The complex secret of the membranes

Researchers at Penn State, the University of Texas at Austin, and DuPont Water Solutions found that the density of the filtration membranes, also down to the atom, can greatly affect how much clean water can be produced.

A desalination membrane acts as a filter for salt water: push the water through the membrane, you get clean water that is suitable for agriculture, power generation and even drinking. The process seems simple, but it contains complex intricacies that have baffled scientists for decades – until now.

Researchers at Penn State, the University of Texas at Austin, Iowa State University, the Dow Chemical Company, and DuPont Water Solutions released an important finding today (December) to help understand how membranes actually filter minerals from water. 31) in science. The article will appear on the cover of the print edition and will appear tomorrow (January). 1).

« Despite their longstanding use, we don’t know much about how water filtration membranes work, » said Enrique Gomez, Penn State professor of chemical and materials science and technology who led the research. “We have found that controlling the density distribution of the membrane at the nano level is very important to the performance of water production. ”

Under the direction of Manish Kumar, Associate Professor in the Department of Civil, Architectural, and Environmental Engineering at UT Austin, the team used multimodal electron microscopy, which combines detailed imaging at the atomic level with techniques that understand chemical composition disclose that desalination membranes are inconsistent in density and mass. The researchers mapped the density fluctuations in the polymer film in three dimensions with a spatial resolution of about one nanometer – that is less than half the diameter of a DNA strand. According to Gomez, this technological advance was key to understanding the role of density in membranes.

« You can see some spots in a coffee filter becoming more or less dense just through your eye, » said Gomez. “It looks uniform in filtration membranes, but not on the nano scale, and how you control that mass distribution is really important to water filtration performance. ”

This came as a surprise, said Gomez and Kumar, since it was previously believed that the thicker the membrane, the less water production is. Filmtec, now part of DuPont Water Solutions, which makes numerous desalination products, partnered with the researchers and funded the project because their in-house scientists discovered that thicker membranes actually turned out to be more permeable.

The researchers found that thickness is less important than avoiding high-density nanoscale regions or « dead zones ». “In some ways, according to Gomez, more even density throughout the membrane is more important than thickness to maximize water production.

This understanding, according to the researchers, could increase membrane efficiency by 30% to 40%, resulting in more water being filtered with less energy – a potential cost-saving update to current desalination processes.

« Reverse osmosis membranes are so widely used to purify water, but we still don’t know a lot about them, » said Kumar. « We can’t really tell how water moves through them, so all of the improvements over the past 40 years have essentially been made in the dark. ”

Reverse osmosis membranes work through one-sided pressure. The minerals stay there while the water passes through. While this is more efficient than desalination processes without a membrane, it still requires an immense amount of energy, the researchers said, but improving the efficiency of the membranes could reduce that burden.

« Freshwater management is becoming a critical challenge worldwide, » said Gomez. “Bottlenecks, droughts – as the storm increases, this problem is expected to become even greater. Having clean water available is critical, especially in areas with limited resources. ”

The team continues to study the structure of the membranes as well as the chemical reactions involved in the desalination process. They also study how the best membranes can be designed for specific materials, e.g.. B.. sustainable yet robust membranes that can prevent the formation of bacterial growth.

« We are advancing our techniques with higher performing materials to clarify the critical factors for efficient filtration, » said Gomez.

Other contributors are lead author Tyler E. . Culp, Kaitlyn P. . Brickey, Michael Geitner, and Andrew Zydney, all affiliated with the Penn State Department of Chemical Engineering; Biswajit Khara and Baskar Ganapathysubramanian, both with the Department of Mechanical Engineering at Iowa State University; Tawanda J. . Zimudzi from the Materials Research Institute (MRI) at Penn State; Jeffrey D. . Wilbur and Steve Jons, both at DuPont Water Solutions; and Abhishek Roy and Mou Paul, both with Dow Chemical Company. Gomez is also linked to the MRI. The microscopic work was carried out on electron microscopes in the Materials Characterization Lab in MRI. DuPont and the National Science Foundation funded the research.

Desalination, research, drinking water, water treatment, purification