Recycling rates for post-consumer textile waste are very low (<0.5%) because the fabrics often consist of tightly interlaced synthetic and natural fibers that require costly sorting and separation processes, and because they often contain dyes and additives that must be addressed. A research team at the University of Delaware (UD; Newark, Del.; www.udel.edu), led by chemical engineering professor Dionisios Vlachos, has developed a method for recycling mixed fabrics made from blends of synthetic fibers, such as spandex, nylon and polyester, with natural fibers, such as cotton.
The process uses a microwave-assisted glycolysis reaction over a zinc-oxide catalyst, followed by solvent dissolution to depolymerize polyethylene terephthalate (PET) and spandex into their respective monomers, while leaving nylon and cotton intact. The approach makes mixed-textile recycling faster and more effective, potentially leading to high-quality recycled materials and greater circularity of the textile industry, the researchers say.
The UD process depends on the use of ethylene glycol (EG), a strong acceptor of microwave radiation, as a solvent. “The microwaves heat up the EG rapidly and help the glycolysis reactions to break down the synthetic fibers,” explains UD graduate student Erha Andini, the first author of a paper published in a recent issue of the journal Science that describes the work.
While the current project was demonstrated at the scale of grams, the team has carried out a techno-economic assessment of the process, and intends to scale it up to larger volumes of fibers. Further refinement of this process holds the potential to achieve a global textile circularity rate of 88%, the researchers wrote.
The effectiveness of the microwave-assisted glycolysis process in completely breaking down polyester and spandex while leaving cotton and nylon intact was surprising, Andini says, even successfully working on samples of unknown composition, she adds.