The superabsorber becomes a liquid under ultraviolet light after absorbing enough water. It can then be reused. Credit: Ken Pekarsky, KIT
Water and UV light effectively and quickly break down the cross-linked polymers in diaper liners without the use of any chemicals. This process allows recycled plastic molecules to be reused for a variety of uses.
Superabsorbent materials such as sodium polyacrylate are important components of a variety of hygiene and medical products, including diapers, bandages, and dressings. These cross-linked polymers are typically insoluble in water, although they are known for their high absorbency. Recycling them traditionally required the use of strong acids.
It will not melt at high temperatures, it will only deteriorate. However, the acid “breaks” the chains and stabilizes the polymer after about 16 hours at 80 degrees. Celsius Therefore, recycling is now possible. Because this process is complex and expensive, superabsorbents are rarely recycled. Approximately 2 million tons of this waste is thrown away or incinerated each year.
Turns into liquid in 5 minutes instead of 16 hours
Researchers from KIT’s Institute of Biochemical Systems, Institute of Biointerfaces, and Institute of Chemical Technology and Polymer Chemistry have discovered that crosslinked sodium polyacrylate polymers degrade under ultraviolet light after uptake of water. .
“The chains that connect the polymers are broken by light, and they are so loose that they swim underwater and turn into liquid fibers,” explains Pavel Levkin, a professor at the Institute of Biochemical Systems. For the study, researchers cut liners from traditional diapers, wetted them with water and exposed them to a 1000 W lamp. After 5 minutes, the solid material turned into a liquid and fell into the collector. “This method using ultraviolet light is about 200 times faster than using acids,” Revkin says.
Recycled polymers can be used in a variety of ways
The team then used known processes to convert the liquid into new adhesives and dyes. “The observation that this substance is soluble and processable was very important. It could probably be turned into many other products,” explains the scientist.
In the test, the researchers used clean diapers. However, it is also possible to separate superabsorbents from used diapers. “Therefore, there is no reason why a near-realistic use should not be possible,” Revkin says. By using solar power, you can optimize recycling methods that are cost-effective and environmentally friendly. “We have discovered a promising strategy to recycle superabsorbents, which significantly reduces environmental pollution and contributes to a more sustainable use of polymers.”
Reference: “From diapers to thickeners and pressure-sensitive adhesives: recycling superabsorbents by UV degradation” by Shuai Li, Johannes M. Scheiger, Zhenwu Wang, Birgit Huber, Maxi Hoffmann, Manfred Wilhelm, Pavel A. Levkin , September 7, 2023 ACS Applied Materials & Interfaces.
DOI: 10.1021/acsami.3c06999
Source: scitechdaily.com
