New research publication supports BioSusTex mission for circular textile recycling

Researchers at Aalto University has developed an effective new method for removing persistent reactive dyes from cotton textile waste, offering a major step forward for sustainable textile recycling and circular fashion systems.

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The study, titled “An effective color stripping process for reactive dyed cotton waste,” was recently published in the journal Industrial Crops & Products. The research introduces a two-step chemical treatment capable of removing up to 99% of color from dyed cotton fabrics while largely preserving the strength and quality of the fibers.

Reactive dyes are among the biggest obstacles in recycling cotton textiles because they form strong covalent bonds with cellulose fibers. These dyes are widely used in the textile industry due to their durability and wash fastness, but they are extremely difficult to remove once garments reach the end of their life cycle. As a result, large volumes of colored textile waste are currently landfilled or incinerated instead of being recycled into new fibers.

The newly developed process combines an alkaline sodium hydroxide treatment followed by sodium chlorite bleaching under acidic conditions. The researchers tested the method on four differently colored cotton fabrics — green, gray, black, and navy — commonly dyed with reactive dyes used in commercial textile manufacturing.

According to the study, the treatment achieved color stripping efficiencies between 97% and 99%, while maintaining high fabric performance. The treated fabrics reached whiteness index values above 80 and lightness values above 85, approaching the appearance of undyed cotton.

Importantly, the process also minimized damage to the textile fibers. The treated fabrics experienced only around 4% weight loss and approximately 12% tensile strength reduction, significantly lower than many previously reported textile stripping technologies. Researchers noted that maintaining fiber quality is essential for enabling high-value fiber-to-fiber recycling applications.

“Our findings demonstrate that effective dye removal can be achieved without relying on extremely high chemical loads or highly destructive treatments,” the authors explained. “This makes the process promising for future circular textile recycling systems.”

The study also investigated the structural and thermal properties of the treated fabrics. Advanced analyses confirmed the successful removal of sulfur-containing reactive dyes while preserving much of the cellulose structure. Researchers observed improved crystallinity in the treated fibers and cleaner thermal degradation behaviour, both indicators of successful purification.

Another important outcome of the study was the possibility of reusing the stripping solutions. The research showed that the treatment chemicals could be effectively reused for up to two additional cycles, reducing chemical consumption, operational costs, and environmental impact.

The work was carried out by researchers Tonmoy Saha, Uyen Le, Md. Reazuddin Repon, Inge Schlapp-Hackl, Tapani Vuorinen, and Ali Tehrani-Bagha at the Department of Bioproducts and Biosystems, School of Chemical Engineering, Aalto University, Finland. The research contributes to ongoing efforts within European textile sustainability initiatives, including the BioSusTex project which focus on advancing circular and sustainable textile technologies.

As the global textile industry faces mounting pressure to reduce waste and transition toward circular production models, innovations such as this could play a key role in enabling large-scale recycling of post-consumer cotton textiles into new high-quality fibers and products. The research team will focus future work on converting the stripped cotton into regenerated fibers through advanced recycling systems, as well as conducting life cycle assessments and techno-economic analyses to evaluate industrial scalability and environmental performance.

You can access and read the paper here: https://doi.org/10.1016/j.indcrop.2026.123480