A complex problem that has baffled scientists for decades has been solved
From:
University of Texas at Austin
December
31, 2020 -- Desalination membranes remove salt and other chemicals from water,
a process critical to the health of society, cleaning billions of gallons of
water for agriculture, energy production and drinking. The idea seems simple --
push salty water through and clean water comes out the other side -- but it
contains complex intricacies 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 reduce costs of clean water production. The researchers determined
desalination membranes are inconsistent in density and mass distribution, which
can hold back their performance. Uniform density at the nanoscale is the key to
increasing how much clean water these membranes can create.
"Reverse osmosis membranes are
widely used for cleaning water, but there's still a lot we don't know about
them," said Manish Kumar, an associate professor in the Department of
Civil, Architectural and Environmental Engineering at UT Austin, who co-led the
research. "We couldn't really say how water moves through them, so all the
improvements over the past 40 years have essentially been done in the
dark."
The findings were published today
in Science.
The paper documents an increase in
efficiency in the membranes tested by 30%-40%, meaning they can clean more
water while using significantly less energy. That could lead to increased
access to clean water and lower water bills for individual homes and large
users alike.
Reverse osmosis membranes work by
applying pressure to the salty feed solution on one side. The minerals stay
there while the water passes through. Although more efficient than non-membrane
desalination processes, it still takes a large amount of energy, the
researchers said, and improving the efficiency of the membranes could reduce
that burden.
"Fresh water management is becoming
a crucial challenge throughout the world," said Enrique Gomez, a professor
of chemical engineering at Penn State who co-led the research. "Shortages,
droughts -- with increasing severe weather patterns, it is expected this
problem will become even more significant. It's critically important to have
clean water availability, especially in low-resource areas."
The National Science Foundation and DuPont,
which makes numerous desalination products, funded the research. The seeds were
planted when DuPont researchers found that thicker membranes were actually
proving to be more permeable. This came as a surprise because the conventional
knowledge was that thickness reduces how much water could flow through the
membranes.
The team connected with Dow Water
Solutions, which is now a part of DuPont, in 2015 at a "water summit"
Kumar organized, and they were eager to solve this mystery. The research team,
which also includes researchers from Iowa State University, developed 3D
reconstructions of the nanoscale membrane structure using state-of-the-art
electron microscopes at the Materials Characterization Lab of Penn State. They
modeled the path water takes through these membranes to predict how efficiently
water could be cleaned based on structure. Greg Foss of the Texas Advanced
Computing Center helped visualize these simulations, and most of the
calculations were performed on Stampede2, TACC's supercomputer.
Journal Reference:
- Tyler
E. Culp et al. Nanoscale control of internal inhomogeneity
enhances water transport in desalination membranes. Science,
Jan 1st, 2021 DOI: 10.1126/science.abb8518
https://www.sciencedaily.com/releases/2020/12/201231141511.htm
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