Mathematical Modelling for Fixed-Bed Column and Batch Adsorption Studies of Antibiotic and CO₂ Capture Using Soybean Stover Biochar

Biochar is a versatile material increasingly recognized for its efficacy in wastewater treatment and environmental remediation. Herein, phosphoric acid-activated soybean stover biochar (ASSB) was prepared via torrefaction under inert atmospheric conditions and evaluated for its adsorption capabilities towards pharmaceutical Norfloxacin (NFX) alongside its CO₂ capture potential. Comprehensive characterization using FT-IR, XRD, SEM, EDX, TGA-DTA, and BET analysis revealed a substantial surface area of 298.82 m² g⁻¹ for ASSB. Batch adsorption studies demonstrated remarkable maximum adsorption capacities of 203.05 mg g⁻¹ for NFX. Response surface methodology (RSM) facilitated the optimization of operational constraints. Isotherm and kinetic analyses indicated that the adsorption of NFX confirmed the Langmuir model and pseudo-second-order kinetics, respectively, with thermodynamic assessments confirming the spontaneity of the adsorption process. Column studies further validated the efficiency of ASSB in large-scale applications. Clark model was found to be the best fit out of non-linear Thomas, Bohart–Adams, and Wolborska column modelling. Regeneration capacity was checked using a gamma irradiation dose of 6 kGy with 84% removal up to the fifth cycle. This study underscores the multifunctional utility of ASSB in pharmaceutical wastewater treatment and CO₂ capture (49.96 cc g⁻¹ at 273 K), highlighting its promising prospects for sustainable environmental applications.