High-Performance Biosorbent from Pyrolyzed Themeda arundinacea for Effective Removal of Textile Dyes: Isotherm, Kinetic, and Thermodynamic Studies

Sustainable removal of textile dyes from wastewater is crucial. Herein, we demonstrate the efficacy of a mesoporous biosorbent, derived from Themeda arundinacea (TAAC), for the adsorptive removal of cationic dyes. Pyrolysis of T. arundinacea yielded 61% activated carbon. TAAC exhibited a high BET surface area (1552 m²/g), micropore volume (0.398 cc/g), and micropore area (1022 m²/g), with mesopores (4.3–5.7 nm). DSC analysis revealed endothermic transitions at 83.1 and 939 °C, indicating the structural changes at high temperature. Equilibrium isotherm capacities were 15 mg/g (MB) and 30 mg/g (MG, CBB). Adsorption studies with methylene blue (MB), malachite green (MG), and Coomassie brilliant blue (CBB) showed rapid dye removal kinetics, best described by pseudo-second-order (MG) and pseudo-first-order (MB) models. The Freundlich model fit the adsorption isotherm for MG and MB. The TAAC’s high surface area and regeneration potential highlight its promise as a sustainable, efficient adsorbent for wastewater treatment.