A new study based in the USA aims to improve the efficiency of desalination membranes by studying the way in which density and mass impacts their ability to produce clean water.
A team of researchers from Penn State University, The University of Texas at Austin, Iowa State University, Dow Chemical Company and DuPont Water Solutions published a key finding for the creation of desalination membranes, which will act as a filter for salty water and provide clean water to be used in agriculture and energy production.
Enrique Gomez, professor of chemical engineering and materials science and engineering at Penn State, who led the research, said: “Despite their use for many years, there is much we don’t know about how water filtration membranes work. We found that how you control the density distribution of the membrane itself at the nanoscale is really important for water-production performance.”
Co-led by Manish Kumar, associate professor in the Department of Civil, Architectural and Environmental Engineering at UT Austin, the team used multimodal electron microscopy, which combines the atomic-scale detailed imaging with techniques that reveal chemical composition, to determine that desalination membranes are inconsistent in density and mass. The researchers mapped the density variations in polymer film in three dimensions with a spatial resolution of approximately one nanometre. According to Gomez, this technological advancement was key in understanding the role of density in membranes.
Gomez said: “You can see how some places are more or less dense in a coffee filter just by your eye. In filtration membranes, it looks even, but it’s not at the nanoscale, and how you control that mass distribution is really important for water-filtration performance.”
Could thicker membranes be more permeable?
Filmtec, now a part of DuPont Water Solutions, which makes numerous desalination products, partnered with the researchers and funded the project because its in-house scientists found that thicker membranes were proving to be more permeable.
The researchers from this study found that the thickness does not matter as much as avoiding highly dense nanoscale regions, or ‘dead zones’. A more consistent density throughout the membrane is more important than thickness for maximising water production. This understanding could increase membrane efficiency by 30% to 40%, according to the researchers, resulting in more water filtered with less energy.
Gomez said: “Freshwater management is becoming a crucial challenge throughout the world. 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 available, especially in low resource areas.”
The team continues to study the structure of the membranes, as well as the chemical reactions involved in the desalination process. They are also examining how to develop the best membranes for specific materials, such as sustainable yet tough membranes that can prevent the formation of bacterial growth.
