The antimicrobial triclosan is widely used in personal hygiene products, textiles and plastics, but when it enters the environment via wastewater, it poses a significant threat to aquatic organisms.
A Cornell research group has developed a cyclodextrin-based fibrous membrane that in lab testing removed approximately 90% of triclosan from water. Their washable and reusable nanofiber material, fabricated via electrospinning - a process that uses an electric field to draw ultra-thin fibers from a liquid - also effectively removed other micropollutants.
"The electrospinning produces a very thin fiber, less than 1 micron in diameter (a human hair is approximately 75 microns), which gives us high surface area and excellent adsorption," said Mahmoud Aboelkheir, doctoral student in human centered design and lead author of "Removal of Pharmaceutical Micropollutants From Aqueous Environment by Electrospun Polycyclodextrin Nanofibrous Membrane," which published Oct. 15 in the journal Separation and Purification Technology.
The senior author is Tamer Uyar, associate professor of fiber science in human centered design in the College of Human Ecology. Co-authors are former Uyar group postdoctoral researcher Asli Celebioglu; Damian Helbling, associate professor in the School of Civil and Environmental Engineering, in Cornell Engineering; and Ivan Keresztes, director of the Cornell NMR and Chemistry Mass Spectrometry Facilities.
In addition to being a threat to aquatic organisms, triclosan has been linked to endocrine disruption, which can cause hormonal imbalance, as well as skin irritation, rashes and other allergic reactions. The chemical is banned in the U.S. in consumer hand and body washes, but is still found in many personal-care products.
Ten years ago, Helbling was part of a research group that invented a porous, cyclodextrin-infused polymer that achieved adsorption rates 200 times that of traditional activated-carbon filtration systems. In the current work, the Uyar group has made a fiber out of cyclodextrin, meaning it can stand alone as filtration material instead of being incorporated onto a polymer or some other material, resulting in even greater filtration potential.
"As fiber scientists, we are always looking for the application of fiber," Uyar said. "So our cyclodextrin membrane is a fiber material, so it can be used as a membrane without a support structure."
In lab testing, the cyclodextrin membrane removed approximately 75% of triclosan in water (11 milligrams per liter concentration) in the first 15 minutes. The membrane reached saturation after six hours, achieving around 88% uptake.
In addition to triclosan, the group's nanofibrous cyclodextrin membrane demonstrated effective removal of ciprofloxacin, an antibiotic used to treat bacterial infections; and oxybenzone, found in sunscreen. According to Aboelkheir, the group tested water from several sources to confirm its efficacy.
"Our collaborators got water samples from Flat Rock and also from some groundwater wells and wastewater treatment plants in the area," he said. "This was an actual test of our membrane, in realistic environments where it could be used, and it still had efficiency in the removal of these micropollutants."
Another benefit of the Uyar group's membrane: reusability. Unlike powdered adsorbents that require a lot of energy to restore them for further use, the cyclodextrin membrane could be easily regenerated just by washing it. And since cyclodextrin is a derivative of corn starch, it's biodegradable and more sustainable than activated carbons, silicas and other non-renewables.
The group confirmed its findings via rotating frame Overhauser enhancement spectroscopy, a type of nuclear magnetic resonance spectroscopy, conducted at the Cornell NMR Facilities.
Ongoing studies in Uyar's lab involve developing advanced cyclodextrin-based nanofibrous membranes designed to capture and remove textile dyes, volatile organic compounds (VOCs), and persistent pollutants like per- and polyfluoroalkyl substances (PFAS), commonly known as "forever chemicals."
This work made use of the NMR and Cornell Center for Materials Research facilities, both supported by the National Science Foundation. Support also came from the Fulbright Foreign Student Program.
