Preparation of novel multifunctional magnetic biochar integrating adsorption and degradation and application in printing and dyeing wastewater

This study focuses on solving the urgent problem of water environment pollution caused by the discharge of organic dyes in high-concentration textile wastewater. A multifunctional magnetic biochar (MMBC-400) with adsorption and degradation functions was prepared by pyrolysis of corn cob and red mud demonstrating efficient handling of Malachite Green (MG). Compared with traditional adsorbents, MMBC-400 combines adsorption and catalytic degradation functions. The adsorption efficiency of MG was 99.19 %, and the adsorption capacity was 793.51 mg/g. The composite material has excellent stability and is still more than 90 % after 6 cycles. The composite material has excellent stability, and the adsorption efficiency is still greater than 90 % after 6 cycles. Kinetic and isothermal analyses showed that the chemisorption was dominated by multilayer adsorption. Meanwhile, the free radical (∙OH, SO- 4·) and non-radical ( 1 O₂, electron transfer) pathways were supplemented to realize the rapid degradation of MG, and the degradation efficiency was greater than 85 % after four regenerations. Characterization studies further confirmed the role of hierarchical pore structure, surface functional groups (e.g., -OH, Fe O), and π-π interactions in pollutant binding. Despite the good experimental results achieved in laboratory scale, future work should address the issues of generalizable application and long-term stability in complex wastewater matrices. This work provides a sustainable strategy for dye removal through the reuse of agricultural and industrial wastes, realizing a paradigm shift from monofunctional materials to multifunctional remediation systems.