Analysis of Leachates in Activated Char from Textile Sources: Implications for Their Use as Adsorbents Arjona, Lourdes Calero De Hoces, Francisca Mónica Quintana, María Alejandra Rodríguez Solís, Rafael Martín Lara, María Ángeles Textile waste Pyrolysis char Sodium thiosulfate activation Textile waste management remains a critical environmental challenge. Valorization through thermochemical routes such as pyrolysis offers a sustainable pathway within the circular economy. In this study, carbonaceous materials were obtained from the pyrolysis of 100% cotton textile residues and subsequently activated with sodium thiosulfate (Na2S2O3). The physicochemical and leaching behaviors of the activated (CA) and non-activated (C) chars were assessed in aqueous solution under controlled pH conditions (3, 7, and 11). Activation significantly increased the specific surface area (from 90 to 975 m2 g−1). Leaching tests revealed that acidic conditions (pH = 3) enhanced the release of major elements following the order Na > Ca > K for C and S > Ca > Na for CA. Despite this, all concentrations of major and trace metals remained well below regulatory discharge limits. Anionic species (Cl−, SO42−) increased slightly after activation but also stayed within safe thresholds, and chemical oxygen demand (COD) values were low (0–9 mg O2 L−1), indicating negligible organic leaching. Overall, the findings show that the structural quality of textile-derived chars was improved by Na2S2O3 activation without compromising their environmental stability, validating their applicability as effective and safe adsorbents for wastewater treatment applications. 2026-02-13T13:19:00Z 2026-02-13T13:19:00Z 2026-02-13 journal article Arjona, L., Calero, M., Quintana, M. A., Solís, R. R., & Martín-Lara, M. Á. (2026). Analysis of Leachates in Activated Char from Textile Sources: Implications for Their Use as Adsorbents. Applied Sciences, 16(4), 1870. https://doi.org/10.3390/app16041870 https://hdl.handle.net/10481/110988 10.3390/app16041870 eng http://creativecommons.org/licenses/by/4.0/ open access Atribución 4.0 Internacional MDPI