Hemp Waste-Derived Activated Carbon for Capecitabine Removal: Kinetic and Isothermal Insights

Capecitabine (CTN) is a widely used oral chemotherapeutic agent frequently detected in hospital effluents and aquatic environments, where it poses serious ecological and toxicological risks. In this study, a high surface area activated carbon derived from hemp waste-derived activated carbon waste was synthesized and evaluated for CTN removal from aqueous solutions. Under optimized conditions (adsorbent dose: 20 mg/50 mL; pH: 7.0; initial CTN concentration: 30 mg/L; contact time: 45 min; temperature: 293 K), a maximum removal efficiency of 99.12% was achieved. Kinetic analysis revealed that the adsorption process followed the pseudo second order model (R² = 0.999; RMSE and MAE minimized), indicating that surface interactions governed the adsorption rate. Equilibrium data were best described by the Langmuir isotherm model (R² = 0.9999), with a maximum adsorption capacity of 167.24 mg/g, confirming monolayer adsorption on a homogeneous surface. Thermodynamic parameters (ΔG° = −11.05 to −15.20 kJ/mol, ΔH° = +47.12 kJ/mol, ΔS° = +197.91 J/mol·K) demonstrated that the process is spontaneous, endothermic, and entropy driven, with improved adsorption at elevated temperatures. These results highlight hemp waste-derived activated carbon waste–derived activated carbon as a sustainable, low cost, and highly effective adsorbent for the removal of capecitabine from aqueous environments.