Researchers at TU Wien have demonstrated a simple way to separate cotton–polyester blended textiles using a solvent made from two inexpensive and non-toxic materials, menthol and benzoic acid. The method, developed by the team led by Nika Depope with senior researcher Andreas Bartl from the Institute of Chemical, Environmental and Bioscience Engineering, offers an approach that could support large-scale textile recycling at a time when global textile production continues to climb. The work responds to a well-documented challenge in the textile industry: mixed fibers are difficult to recycle because each material requires a different treatment, and separating them without degradation has largely remained inefficient or costly.
Depope, N., Depope, A., Archodoulaki, V.-M., Ipsmiller, W., & Bartl, A. (2025). Deep eutectic solvent as a solution for polyester/cotton textile recycling. Waste Management, 208, 115177. https://doi.org/10.1016/j.wasman.2025.115177
Menthol and benzoic acid are solids at room temperature, but when combined in the right ratio they form what is known as a deep eutectic solvent. These types of solvents have attracted attention over the past decade because they are easy to prepare, generally safer to handle than traditional industrial solvents, and can be tuned for specific chemical tasks. When heated to around 216 °C, the mixture used by the TU Wien researchers begins to dissolve polyester while leaving cotton fibers intact. Tests conducted in the lab showed that blended fabrics could be separated in roughly five minutes under these conditions.
Nika Depope with senior researcher Andreas Bartl from the Institute of Chemical Environmental and Bioscience Engineering stated,
“What may be surprising at first: both menthol and benzoic acid are solid at room temperature. But together they form a liquid; a so-called deep eutectic solvent. This novel liquid is a powerful, nontoxic and easy-to-produce solvent with a wide range of possible applications.”
According to the team’s analyses, the cotton fibers remain structurally stable after treatment and can be washed, dried, and spun again. The polyester, once cooled, precipitates out of the solvent and can be filtered off without signs of chemical breakdown. This aspect is important because many existing recycling methods rely on depolymerization, splitting polyester into smaller building blocks that must then be reprocessed. Preserving the polymer chains simplifies reuse and improves the likelihood that the recycled material can substitute for virgin polyester in manufacturing.
Reports from TU Wien’s internal communication and independent coverage of the study emphasize the recovery rates reached in the experiments. Cotton was recovered completely, and polyester at roughly ninety-seven percent, making the method close to a closed-loop separation process. The researchers note that the solvent itself is simple to regenerate and can be reused, though long-term cycling tests are still under way to understand how its performance changes over repeated runs.
The study also acknowledges the current constraints. The temperature required for separation is relatively high, and any industrial deployment would have to address the associated energy demand. Depope and Bartl’s team is working on reducing the operating temperature or improving heat-transfer efficiency. Energy modeling is being incorporated into the next phase of development, along with collaborations with textile-processing partners to test the method on larger batches of fabric and more complex blends.
Although the work remains at the lab scale, the underlying principle is straightforward, and several textile-engineering commentators have pointed out its compatibility with existing recycling lines. Because neither fiber type is chemically modified, the recycled materials could be fed into conventional spinning, extrusion, or nonwoven production without extensive remediation. This positions the approach as a potential complement to other recycling technologies rather than a replacement.
The research, published in Waste Management, adds to a growing interest in chemical separation methods that prioritize material preservation over breakdown. As textile waste continues to accumulate worldwide, solutions that make blended fabrics easier to recover are expected to play an important role in future recycling infrastructure. The TU Wien team’s solvent system offers one possible route, balancing practicality with material quality, and providing a foundation for larger-scale development.
Adrian graduated with a Masters Degree (1st Class Honours) in Chemical Engineering from Chester University along with Harris. His master’s research aimed to develop a standardadised clean water oxygenation transfer procedure to test bubble diffusers that are currently used in the wastewater industry commercial market. He has also undergone placments in both US and China primarely focused within the R&D department and is an associate member of the Institute of Chemical Engineers (IChemE).
