Mechanochemically modified biogenic silica with Zn-Al domains for reversible imatinib mesylate capture and recovery under batch and continuous-flow conditions

The increasing occurrence of cytostatic drugs in aquatic environments has raised concern because of their biological activity, persistence, and incomplete removal by conventional wastewater treatment. Here, a Zn-Al-modified rice husk-derived silica nanohybrid was prepared mechanochemically and evaluated for imatinib mesylate (IM) adsorption and recovery under batch and continuous-flow conditions. Although the specific surface area decreased from 275 to 164 m 2 g −1 after modification, the hybrid showed higher IM adsorption than its individual components. Adsorption was pH-responsive, with charge-dependent interactions likely contributing together with interactions involving hydroxylated and oxygen-containing surface groups. Among the tested equilibrium models, Sips provided the most consistent overall description, yielding a model-derived saturation capacity of 147.82 mg g −1 at 298.15 K, whereas the highest experimentally measured capacity was 93.80 mg g −1 . Thermodynamic analysis indicated a spontaneous and endothermic process (ΔH° = 44.19 kJ mol −1 ). IM removal in surface water reached 92.34%, while stronger matrix effects occurred in drinking water treatment plant effluent and groundwater. Desorption with 0.1 M HCl reached 94.51%, and adsorption capacity remained between 21.98 and 24.60 mg g −1 over ten adsorption-desorption cycles, with 95.70% adsorbent mass recovery. In continuous flow, breakthrough and saturation occurred at 1080 and 3900 min, with useful and total dynamic adsorption capacities of 214.7 and 407.7 mg g −1 after accounting for glass-wool retention. Acidic elution of the complete packed system produced an overall IM recovery of approximately 98% and a maximum eluate concentration 3.82-fold higher than the influent, supporting further evaluation for continuous-flow adsorption and preconcentration applications.