A team of researchers at Penn State university has used the latest in microscopy to model the internal structure of a desalination membrane, seeking to improve the technology.
The team led by professor of chemical engineering Enrique Gomez, investigated the internal structure of polyamide film using high-angle annular dark field scanning transmission electron microscopy (HAADF-STEM) tomography. The image intensity of HAADF-STEM is directly proportional to the density of the material, enabling it to be mapped to nanoscale resolution.
HAADF-STEM enabled the researchers to construct a three-dimensional model of the membrane’s internal structure, and to analyse the structural components, determining which characteristics might be manipulated to improve membrane life, reduce resistance to fouling, and enhance recovery.
Gomez said: “We found that the density of the polyamide layer varies throughout the film. This potentially changes the way engineers think about how water moves through the material, because resistance to flow is not homogeneous, and is highest at the membrane surface.
“Knowing what the material looks like on the inside, and understanding how this microstructure affects water transport properties, is crucial to designing next-generation membranes with longer operational lifetime that can function under a diverse set of conditions,” he added.
The Dow Chemical Company and National Science Foundation sponsored the work, which was a collaboration between Penn State and Dow Chemical Company.