Microwave Assisted Glycolysis: A Chemical Solution to Textile Waste Management

   

Piles of discarded clothes wait to be sorted at a textile-recycling factory in Taiwan.

    Every year, millions of tons of clothing are discarded, nearly three quarters of which end up being incinerated or dumped into landfills which end up as microplastics polluting our oceans. The solution to this is a newly developed chemical-processing technique that can break down fabrics into reusable materials. A recent Nature article highlights the discovery.

    Recycling is a tricky process; Much of it involves physically separating waste into raw materials. Recycling of textiles becomes even trickier. Many fabrics are made of a mixture of materials such as cotton and polyester which mechanical recycling methods often struggle to separate into products that can be used again. When separation is possible, the quality of the product is often low and not worth reusing. 

    A newly developed chemical process called microwave assisted glycolysis can break up large chains of molecules called polymers into their smaller, monomer units, with the help of heat and a zinc oxide (ZnO) catalyst. For pure polyester fabrics, the reaction converts the polyester into BHET (Bis(2-Hydroxyethyl) terephthalate) with 90% yield. The main advantage of this technique though, is its ability to process textiles that have mixed composition. The researchers tested fabrics containing a blend of cotton, polyester, nylon or spandex. Like polyester, spandex was broken down into its monomer units called MDA (4,4′-methylenedianiline). Both MDA and BHET products of the reaction can be used directly to make new clothing. Cotton and nylon on the other hand, were found to not be affected by the treatment and could thus be recovered intact. 

Overview of the chemical recycling process.

    Another significant advantage of microwave assisted glycolysis is its relatively low reaction time. The reaction takes only 15 minutes which is significantly lower than other processing techniques which can take days to break down the same materials. Dionisios Vlachos, co-author of the study and professor of Chemical & Biomolecular Engineering at the University of Delaware, states that he believes reaction conditions can be further optimized to bring reaction times down to the order of seconds. With further developments, the researchers estimate that 88% of clothing worldwide could be recycled.

Sources

Andini, Erha, et al. “Chemical recycling of mixed textile waste.” Science Advances, vol. 10, no. 27, 5 July 2024, https://doi.org/10.1126/sciadv.ado6827.

Kudiabor, Helena. “‘Chemical Recycling’: 15-Minute Reaction Turns Old Clothes into Useful Molecules.” Nature News, Nature Publishing Group, 4 July 2024, www.nature.com/articles/d41586-024-02210-1.