Researchers at North Carolina State University (NC State) are trying to reduce the amount of textile waste using enzymes to separate cotton-polyester blends, making it possible to recycle both materials.
Normally, polyester does not degrade in landfills and cotton may take several months or more to break down, says Sonja Salmon, associate professor of textile engineering, chemistry and science at NC State.
“Using our method, we can separate the cotton from polyester in less than 48 hours,” Salmon says.
The researchers accomplished this feat using a mixture of enzymes in a mildly acidic solution to cut up the cellulose in the cotton, leaving small cotton fiber fragments and glucose.
Then, they washed away the glucose in 50 C water (122 F) to filter out the cotton fiber fragments, separating the cotton from the polyester.
For dyed or chemically treated fabrics, such as for wrinkle resistance, however, additional steps were required. In order to break down the dyed materials, the number of enzymes and time were increased, and for fabrics treated with durable press chemicals, a pretreatment was used before the enzymes were added.
“The dye that you choose has a big impact on the potential degradation of the fabric,” says Jeannie Egan, a graduate student at NC State. “We found the biggest obstacle so far is the wrinkle-resistant finish. The chemistry behind that creates a significant block for the enzyme to access the cellulose. Without pretreating it, we achieved less than 10% degradation, but after, with two enzyme doses, we were able to fully degrade it, which was a really exciting result.”
This study was published in Resources, Environment and Sustainability journal in September 2023.