Optimising textile waste pyrolysis for high-performance activated carbons: Fibre-dependent behaviour and synergistic effects in mixed waste streams

The growing volume of textile waste requires efficient valorisation strategies that go beyond energy recovery. This study investigates the pyrolysis and subsequent KOH activation of major textile fibres (cotton, viscose, polyester, wool) and their realistic mixtures to produce high–surface–area activated carbons. The effects of temperature (400–700 °C) and residence time (15–60 min) on char yield and pore development were systematically evaluated. Cellulosic fibres reached maximum BET surface areas at 500 °C, whereas polyester and wool required 600 °C and 700 °C, respectively. KOH activation produced highly microporous carbons (1659–3504 m 2 /g, >90% micropore contribution). Most pore development occurred within the first 30 min of pyrolysis. Strong positive synergistic effects were observed for fibre mixtures at 500 °C, where the experimental BET surface area exceeded the theoretical additive value by approximately 49%. The activated carbons showed excellent methylene blue adsorption (1284–3003 mg/g), which fitted the most to the Langmuir isotherm model. Importantly, the favourable performance of materials derived from cotton and polyester, which are the dominant components of global textile waste streams, suggests that strict fibre separation prior to thermochemical treatment may not be necessary. These findings provide new insights into pore formation in multicomponent textile systems and highlight the potential of mixed textile waste as a feedstock for high–performance carbon adsorbents within circular economy frameworks.