Recycling: Researchers separate cotton from polyester in blended fabric


Date:
March 20, 2023
Source:
North Carolina State University
Summary:
Researchers 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.


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FULL STORY ==========================================================================
In a new study, North Carolina State University researchers 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.

"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." According to the
U.S. Environmental Protection Agency, 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. Cellulose is the
material that gives structure to plants' cell walls. 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. Glucose is 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.

"It's quite promising that we can separate the polyester to a clean
level," Salmon added. "We still have some more work to do to characterize
the polyester's properties, but we think they will be very good because
the conditions are so mild. We're just adding enzymes that ignore
the polyester." They 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. In order 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, they had to use a chemical pre-treatment
before adding the enzymes.

"The dye that you choose has a big impact on the potential degradation
of the fabric," said 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, with two enzyme doses,
we were able to fully degrade it, which was a really exciting result." 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." The study,
"Enzymatic textile fiber separation for sustainable waste processing,"
was published in Resources, Environment and Sustainability. Co- authors included Siyan Wang, Jialong Shen, Oliver Baars and Geoffrey Moxley.

Funding was provided by the Environmental Research and Education
Foundation, Kaneka Corporation and the Department of Textile Engineering, Chemistry and Science at NC State.

* RELATED_TOPICS
o Plants_&_Animals
# Biology # Fisheries # Biochemistry_Research
o Matter_&_Energy
# Textiles_and_Clothing # Wearable_Technology #
Materials_Science
o Earth_&_Climate
# Hazardous_Waste # Recycling_and_Waste #
Environmental_Issues
* RELATED_TERMS
o Enzyme o Parachute o Cotton o Antioxidant o Asbestos o
Autocatalysis o Recycling o Hazardous_waste

========================================================================== Story Source: Materials provided
by North_Carolina_State_University. Original written by Laura
Oleniacz. Note: Content may be edited for style and length.


========================================================================== Journal Reference:
1. Jeannie Egan, Siyan Wang, Jialong Shen, Oliver Baars, Geoffrey
Moxley,
Sonja Salmon. Enzymatic textile fiber separation for sustainable
waste processing. Resources, Environment and Sustainability, 2023;
13: 100118 DOI: 10.1016/j.resenv.2023.100118 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2023/03/230320143826.htm

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