A recent study, published in Science Advances, by Case Western Reserve University researchers reveals that manufactured porous separation materials often fail to function as intended because their pores are blocked by excess polymer, leading to inefficiencies and higher costs. Using single-molecule microscopy, they found that molecules primarily diffuse and adsorb around the outer edges, leaving the material’s center largely unused.
Lydia Kisley. Image Credit: Case Western Reserve University
Separating useful molecules from mixtures of other substances costs $4 billion a year, produces 100 million tons of carbon dioxide, and uses 15% of the country's energy.
For instance, commercial manufacturers create columns of porous materials to separate possible new drugs created by the pharmaceutical industry. These materials are also used in environmental science, energy and chemical production, and the production of foods and beverages.
Lydia Kisley and Ambrose Swasey - Assistant Professor of Physics and Chemistry at Case Western Reserve - were involved in the study.
Porous Materials that are not Porous
These materials are marketed as ‘fully porous,’ but they aren’t. We were really surprised by this. Why isn’t this material working the way it was designed and is being sold to work?
Lydia Kisley, Study Lead, Case Western Reserve University
Kisley and colleagues Professor Burcu Gurkan and Associate Professor Christine Duval from the Department of Chemical and Biomolecular Engineering at the Case School of Engineering wanted to know why.
Seeing with a Microscope
Kisley observed molecular dynamics at the nanoscale using single-molecule fluorescence microscopy, a specialized technique that enables researchers to observe and examine the behavior of individual molecules.
We use light to be able to observe individual molecules, shining a bluer laser to get the molecules to fluoresce in red.
Lydia Kisley, Study Lead, Case Western Reserve University
Gurkan and Muhammad Zeeshan, a postdoctoral researcher in Kisley lab, initially tested the materials according to industry specifications rather than the solution conditions in which they are used and discovered that they performed as the manufacturers had claimed.
However, Kisley discovered that the manufacturers were adding so much cellulose material to capture molecules that it blocked the pores when he imaged the same materials under conditions used in actual separations. Removing excess material with a solvent enhanced the potential separations.
Improving Separations for Industry
Kisley anticipates that their research will assist producers in creating more effective separations.
Half the cost of bringing a new drug to market is trying to separate molecules, a process which may be done between 10 and 20 times for one substance.
Lydia Kisley, Study Lead, Case Western Reserve University
The performance of separators can be predicted and their actual operation is demonstrated using the single-molecule microscopy technique. According to Kisley, if the industry adopts this, separation science could do away with its current trial-and-error approach.
“Maybe you could get more efficient separations and eliminate an entire step. Think of the monetary and time savings. We could converge faster on the successful drug to help treat disease,” said Kisley.
Kisley credited Ricardo Monge Neria, a physics graduate student at Case Western Reserve, spearheading the experimental investigation and writing the published study.
Researchers from the Case School of Engineering Swagelok Center for the Surface Analysis of Materials and Rachel Saylor, an Associate Professor of Chemistry and Biochemistry at Oberlin College, also worked together on the study.