Researchers from North Carolina State University found they could separate blended cotton and polyester fabric using enzymes — nature’s tools for speeding chemical reactions.
Ultimately, they hope their findings will lead to a more efficient way to recycle the fabric’s component materials, thereby reducing textile waste. However, they also found the process need more steps if the blended fabric was dyed or treated with chemicals that increase wrinkle resistance.
The study, “Enzymatic textile fiber separation for sustainable waste processing,” was published in Resources, Environment and Sustainability and was co-authored by Siyan Wang, Jialong Shen, Oliver Baars and Geoffrey Moxley.
“We can separate all of the cotton out of a cotton-polyester blend, meaning now we have clean polyester that can be recycled,” said 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.”
In the study, researchers used a “cocktail” of enzymes in a mildly acidic solution to chop up cellulose in cotton. The idea is to chop up the cellulose so it will “fall out” out of the blended woven structure, leaving some tiny cotton fiber fragments remaining, along with glucose, the biodegradable byproduct of degraded cellulose. Then, their process involves washing away the glucose and filtering out the cotton fiber fragments, leaving clean polyester.
“This is a mild process — the treatment is slightly acidic, like using vinegar,” Salmon said. “We also ran it at 50 degrees Celsius, which is like the temperature of a hot washing machine.
Researchers said 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 resist a very powerful enzymatic degradation,” Salmon said. “It has potential value as a strengthening agent. 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.”