Enhancing Cellulose Reactivity in Textile Waste via Cold-Alkali Swelling

Global fiber demand is rising rapidly, yet less than 1% of discarded textiles are recycled into new materials. Here, cold-alkali swelling followed by acid reprecipitation was investigated as a pretreatment to improve cellulose accessibility and reactivity in textile-waste feedstocks. Two recycled cotton-based textiles were compared with cotton linters and dissolving wood pulp. Swelling was performed in 10 wt% NaOH at –20°C, followed by reprecipitation and washing. Cold-alkali treatment increased water retention value (WRV) for all samples, reaching 3.0 g g ⁻¹ for recycled pure-cotton textile, 2.5 g g ⁻¹ for the cotton–synthetic blend, and 1.6 g g ⁻¹ for both cotton linters and dissolving wood pulp. Initial acid-hydrolysis rates increased from 9.0 to 26.3 mg l ⁻¹ min ⁻¹ for cotton linters, 10.0 to 27.5 mg l ⁻¹ min ⁻¹ for dissolving wood pulp, 11.6 to 28.8 mg l ⁻¹ min ⁻¹ for recycled pure-cotton textile, and 12.9 to 22.4 mg l ⁻¹ min ⁻¹ for the cotton–synthetic blend. These increases occurred despite moderate intrinsic-viscosity losses of 7-26%, depending on feedstock. X-ray diffraction showed broader and less-resolved diffraction peaks after swelling and reprecipitation, with crystallinity index values decreasing from 90% to 63% for cotton linters, from 78% to 66% for dissolving wood pulp, from 89% to 61% for recycled pure-cotton textile, and from 85% to 50% for the cotton–synthetic blend. Overall, cold-alkali swelling and reprecipitation improved cellulose accessibility and reactivity in textile-derived feedstocks and offer a practical pretreatment route for upgrading low-value cotton-rich waste toward regenerated-cellulose and cellulose-derivative processes.