Water and UV radiation break down cross-linked diaper core polymers quickly and efficiently without the need for chemicals. The recycled molecules can then be used in different ways.
Absorbent granules are found in diapers and in a number of other hygienic and medical products, such as bandages and incontinence pads. Until now, strong acids were needed to recycle sodium polyacrylate, the highly absorbent material. These cross-linked polymers are insoluble in water. At high temperatures they do not melt, but only break down. However, the acids ‘cut’ the chains after 16 hours at 80 degrees Celsius and thus make recycling possible. This process is complex and expensive and therefore absorbent granules are hardly reused. Every year, approximately two million tons end up in the trash or are incinerated.
Liquid in five minutes
Researchers from the Institute for Biological and Chemical Systems, the Institute for Biological Interfaces and the Institute for Chemical Technology and Polymer Chemistry at KIT have now discovered that the cross-linked sodium polyacrylate polymers break down under UV light after absorbing water. “The chains connecting the polymers are broken by light. Then they are so loose that they swim in water and turn into liquid fibers,” says Pavel Levkin, professor at the Institute of Biological and Chemical Systems. For their study, the researchers cut the inserts from conventional diapers, moistened them with water and exposed them to a 1,000 W lamp. After just five minutes, the solid material turned into a liquid that fell into a collector. “This method with UV light is about 200 times faster than with acids,” says Levkin.
The team then used known processes to convert the liquid into new adhesives and dyes. “The observation that the substance is soluble and processable was of great importance. Most likely, many other products can be made from it.”
The researchers used clean diapers for their tests. But it is also possible to separate the absorbent granules from used diapers. “So there’s no reason why a usage close to reality shouldn’t be possible,” Levkin says. The recycling method can be ecologically optimized free of charge by using solar energy. “We have found a promising strategy for recycling superabsorbers. This will significantly reduce environmental pollution and contribute to a more sustainable use of polymers.”
2023-10-30 15:00:32
#Diapers #recycled #times #faster #light #News #KunststofenRubber.nl #Plastic #Rubber
