Preparation and Adsorption Performance of Walnut Waste-Based Magnetic Activated Carbon with High Specific Surface Area

Magnetic activated carbon (MAC) derived from agricultural waste shows significant potential for the removal of norfloxacin (NOR) from wastewater. However, understanding the removal mechanisms, efficiency, and recyclability of MAC produced from walnut green husk and ferrocene for NOR remains a challenge. In this study, walnut green husk-based MAC (HQP-MC) was synthesized, and changes in surface functionality, mechanisms for NOR removal, and major influencing factors were investigated. The results indicated that HQP-MC predominantly features a mesoporous structure with a diverse array of surface functional groups, including -OH, NH₂, C=O, and C-O. Additionally, HQP-MC demonstrates a remarkable adsorption capacity for NOR, achieving 226.8 mg·g^-1 at 298 K and pH 7.0 under various substrates and experimental conditions. This high capacity can be attributed to a significantly enhanced specific surface area and pore volume, which increased by factors of 2.40 and 2.46, respectively, compared with pristine activated carbon. Moreover, HQP-MC exhibited an exceptional saturation magnetic strength of 11.5 emu·g^-1, along with a reusability rate of 80.5% after ten cycles. The adsorption kinetics were effectively described by the pseudo-second-order model and the Langmuir isotherm model. This study provides valuable insights into the sustainable development of magnetic adsorbent materials derived from agricultural waste and their applications in wastewater decontamination.