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.

This research investigated the effect of the synthesis conditions on the adsorption capacity of hydrochar (HC) derived from Rosa rubiginosa stems via hydrothermal carbonization. HC samples were prepared at 180, 200 and 220 °C using masses with three different raw-material-to-water ratios (i.e., 5, 7.5 and 10 g of biomass in 80 mL of water), obtaining yields between 43 and 57%. The point of zero charge (PZC) of all samples was determined, obtaining the highest value (5.36) for the sample prepared at 180 °C using 5 g of biomass: 80 mL water ratio (HC5_180). This sample exhibited a crystallinity index value (I_D/I_G, determined by Raman Spectroscopy) of 1.73, which is indicative of a higher degree of structural disorder, related to a greater presence of defects generated by surface functional groups, which, in turn, was identified by infrared spectroscopy. Adsorption tests were conducted using methylene blue (MB), achieving 76.3% removal at an initial concentration of 2.5 mg/L. Adsorption isotherms were also obtained for each HC type, which were fitted to the Langmuir and Freundlich models to elucidate the adsorption mechanism, while kinetic studies were performed on the HC5_180 sample. The findings demonstrate that HC adsorption capacity is governed by the distribution and type of surface functional groups. Thus, the valorization of floral industry by-products into biosorbents, as HC, promotes the circular economy, converting operational waste into a sustainable raw material with added commercial value.