Biological membranes can achieve remarkably high permeability, while maintaining the ideal selectivity by relying on homogeneous internal structures in the form of membrane proteins. In new research, a team of scientists led by Penn State University and the University of Texas at Austin have applied such design strategies to desalination of polyamide membranes.
This 3D model of a polymer desalination membrane shows water that avoids dense patches in the membrane and slows flow; red above the membrane shows water under higher pressure and with higher salt concentrations; the golden, granular, spongy structure in the middle shows denser and less dense areas within the saline stop membrane; silver channels show how water flows through; and the blue below shows water under lower pressure and with lower concentrations of salt. Image Credit: Ganapathysubramanian Research Group / Iowa State University / Gregory Foss, Texas Advanced Computing Center.
Dr. Enrique Gomez, dr. Manish Kumar and their colleagues from Iowa State University, Penn State University, the University of Texas at Austin, DuPont Water Solutions and Dow Chemical Co., found that creating a uniform membrane density to the nanoscale of billionths. of a meter is crucial for the maximum performance of reverse osmosis, water filtration membranes.
Using transmission electron microscope measurements of four different polymer membranes used for desalination of water, they predicted the prediction of water by 3D models of the membranes, so that a detailed comparative analysis of why some membranes perform better than other.
“The simulations could succeed in having more uniform membranes and no ‘hot spots’ levels and better performance. The secret ingredient is less inhomogeneity, ”said Professor Baskar Ganapathysubramanian, a researcher at Iowa State University.
“Just look at the image we created using the Texas Advanced Computing Center,” added Biswajit Khara, a doctoral student at Iowa State University.
“We show how the water concentration across the membrane changes,” said Professor Ganapathysubramanian.
“This is beautiful. It has not been done before because such detailed 3D measurements were not available, and also because such simulations are not trivial to perform.”
“The simulations themselves posed computer challenges, as the diffusivity within an inhomogeneous membrane can vary by six orders of magnitude,” Khara said.
The key to better desalination membranes is to figure out how to measure and control the density of manufactured membranes on a very small scale.
Manufacturing engineers and materials scientists need to make the density throughout the membrane uniform and thus promote water flow without compromising salt removal.
“These simulations provided a lot of information to determine the key to making desalination membranes more effective,” said Professor Ganapathysubramanian.
The team’s work appears in the journal Science.
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Tyler E. Culp et al. 2021. Nanoscale control of internal inhomogeneity increases the transport of water in desalination membranes. Science 371 (6524): 72-75; doi: 10.1126 / science.abb8518