Atakan Toprak, Muhammet Hüseyin Çokal
In this study, high-surface-area magnetically activated carbon nanocomposites were synthesized from sustainably sourced chestnut shells via a hydrothermal process, followed by chemical activation with ZnCl 2 at 550–950 °C, and then magnetization. Physicochemical characterization using BET, XRD, SEM-EDS, FTIR, VSM, and XPS confirmed the successful integration of Fe 3 O 4 nanoparticles into the highly porous activated carbon matrix. MAC850 was identified as the most suitable adsorbent, exhibiting a superior BET specific surface area of 1802 m 2 /g and a total pore volume of 1.25 cm 3 /g. Adsorption experiments for MB removal showed that the process followed pseudo-second-order kinetics (R 2 = 0.99). The equilibrium data fit both the Langmuir and the Freundlich isotherm models, and MAC850 achieved an exceptional maximum monolayer adsorption capacity (Q 0 ) of 1020.4 mg/g, significantly outperforming many previously reported biomass-derived magnetic adsorbents. Furthermore, MAC850 demonstrated remarkable reusability, maintaining a removal efficiency of 75% after five regeneration cycles. The adsorption mechanism is attributed to the synergistic interaction of electrostatic attraction, π-π stacking, hydrogen bonding, and significant pore filling within the hierarchical porous network. These results highlight the potential of MAC derived from chestnut shells as a highly effective, renewable, and magnetically separable adsorbent for the sustainable treatment of wastewater contaminated with cationic dyes.