Researchers Separate Cotton from Polyester in Blended Fabric
May 1, 2023 In a new study, North Carolina State University researchers found they could separate blended cotton and polyester fabric using enzymes, hoping that their findings will lead to a more efficient way to recycle the fabric’s materials to reduce textile waste.
However, they also found the process needs more steps if the blended fabric was dyed or treated with chemicals that increase wrinkle resistance.
“We can separate all of the cotton out of a cotton-polyester blend, meaning now we have clean polyester that can be recycled,” says the study’s corresponding author Sonja Salmon, Associate Professor of Textile Engineering, Chemistry, and Science at NC State. “In a landfill, the polyester is not going to degrade, and the cotton might take several months or more to break down. Using our method, we can separate the cotton from polyester in less than 48 hours.”
According to the U.S. EPA, consumers throw approximately 11 million tons of textile waste into U.S. landfills each year. Researchers wanted to develop a method of separating the cotton from the polyester so each component material could be recycled.
In the study, researchers used a cocktail of enzymes in a mildly acidic solution to chop up cellulose in cotton, allowing it to “fall out” out of the blended woven structure, leaving some tiny cotton fiber fragments remaining, along with glucose (the biodegradable byproduct of degraded cellulose). The glucose is then washed away, and the cotton fiber fragments are filtered from the polyester.
The researchers compared degradation of 100% cotton fabric to degradation of cotton and polyester blends, and also tested fabric that was dyed with red and blue reactive dyes and treated with durable press chemicals. To break down the dyed materials, the researchers had to increase the amount of time and enzymes used. For fabrics treated with durable press chemicals, a chemical pre-treatment was used before adding the enzymes.
“The dye has a big impact on the potential degradation of the fabric,” says the study’s lead author Jeannie Egan, a graduate student at NC State. “Also, 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 pre-treating it, we achieved less than 10% degradation. But after two enzyme doses, we were able to fully degrade it.”
Researchers say the polyester could be recycled, while the slurry of cotton fragments could be valuable as an additive for paper or useful addition to composite materials. They’re also investigating whether the glucose could be used to make biofuels.
“The slurry is made of residual cotton fragments that have potential value as a strengthening agent,” Salmon says. “For the glucose syrup, we’re collaborating on a project to see if we can feed it into an anaerobic digester to make biofuel. We’d be taking waste and turning it into bioenergy, which would be much better than throwing it into a landfill.”
The study, “Enzymatic textile fiber separation for sustainable waste processing,” was published in Resources, Environment and Sustainability. Co-authors included Jeannie Egan, Siyan Wang, Jialong Shen, Oliver Baars,, and Geoffrey Moxley, and Sonja Salmon. Funding was provided by the Environmental Research and Education Foundation, Kaneka Corporation, and the NC State Department of Textile Engineering, Chemistry, and Science.
Source: North Carolina State University
GET THE NEWSLETTER TODAY!
