Coffee Husk-Derived Activated Carbon for the Adsorptive Removal of Imatinib Mesylate from Water: Kinetic, Isotherm, Thermodynamic, and DFT Studies

Coffee husk-derived activated carbon prepared by H3PO4 chemical activation was investigated for the removal of imatinib mesylate from aqueous solutions. Structural and chemical characterization using N2 physisorption, SEM, FTIR, Raman spectroscopy, and thermogravimetric analysis revealed a porous carbon matrix containing oxygenated functional groups and a defective turbostratic structure. The adsorption behavior was evaluated through batch experiments by examining the effects of pH, adsorbent dosage, particle size, contact time, and initial drug concentration. Under optimized conditions (300 µm particle size, 0.6 g adsorbent dosage, and pH 6), imatinib mesylate removal reached 97.9%, with equilibrium achieved within 60 min. The adsorption kinetics followed the pseudo-second-order model (R2 = 0.946–0.984), while equilibrium data were best described by the Sips isotherm model (R2 > 0.99), indicating adsorption on a heterogeneous surface. Density functional theory calculations confirmed the contribution of oxygen-containing groups, with carboxyl-functionalized carbon exhibiting the strongest interaction with imatinib mesylate (−105.3 kJ mol−1). These findings highlight the potential of coffee husk-derived activated carbon as a sustainable adsorbent for pharmaceutical contaminant removal.