One of the most pressing environmental challenges is textile wastewater with high chemical oxygen demand (COD). Another critical issue is the underutilization of lignocellulosic waste, such as sesame press cake (SPC). While SPC is a promising source of cellulose, conventional acidic extraction methods generate toxic effluents, further contributing to environmental pollution. This study proposes a circular economy strategy to concurrently address both challenges. Cellulose was extracted from SPC using a recycle flow reactor with nitric acid as the solvent. Interestingly, the acidic effluent was combined with alkaline-treated marble waste (MW) under pyrolysis (350 °C, 30 min) to synthesize a magnetic lignocellulosic‑calcium adsorbent (BFa), which effectively reduced the COD of textile wastewater. This method simultaneously enabled the treatment and valorization of acidic effluent, textile wastewater, and MW. The results demonstrated that the extracted semi-crystalline cellulose from SPC (yield: 22.91 %) exhibited a wrinkled, rough morphology. The BFa adsorbent, with a specific surface area of 35.98 m2/g, achieved 99 % COD removal (initial COD: 2200 ± 100 mg O2/L) at an optimal dosage of 40 g/L, with an equilibrium adsorption amount of 55 mg/g. The adsorption process was spontaneous, endothermic, and followed a multilayer heterogeneous mechanism, as indicated by the Freundlich isotherm, with kinetics best described by a pseudo-second-order model. Techno-economic analysis revealed that this approach offers a cost-effective textile wastewater treatment solution at $0.081/1000 COD removal with BFa production costing $4.45/kg. Furthermore, the integrated process combines wastewater treatment with cellulose production ($34.04/kg), establishing a sustainable circular economy model.

Keywords