Researchers from The University of Texas at Austin and Penn State have taken a step toward developing a cost-effective desalination membrane that could provide clean water for drinking and irrigation. The researchers collaborated with DuPont Water Solutions to look at the nanostructure of membranes in order to better understand why desalination is still such an enigmatic science. Their findings were published recently in Science.
"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 process of reverse osmosis with membranes requires large amounts of energy. The researchers found that desalination membranes do not function efficiently if the density is not uniform at the nanoscale, so they figured that tweaking the nanoscale density of a membrane could in turn enhance its efficiency.
"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. "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 group found that, contrary to thought, thicker membranes showed to be more permeable and ultimately more efficient. Using electron microscopy, the scientists modeled the movement of water through membranes to predict how to increase efficiency. Their simulations were able to show an increase in efficiency of 30%-40%, which means that their membranes cleaned more water with less energy.
Ultimately the determination that density fluctuations reduce water movement within a membrane was key to enhancing permeability and efficiency. The researchers say that this understanding could promote access to clean water as well as cut expenses for water.