A recyclable magnetic biochar from corn cobs and red mud for treating complex contaminants containing dyes and heavy...

The treatment of wastewater co-contaminated with organic dyes and heavy metals remains challenging due to competitive adsorption. Herein, a magnetic multifunctional biochar (MMBC-400) was synthesized from corn cobs and red mud for the simultaneous removal of malachite green (MG) and Pb²⁺. In single systems, MMBC-400 exhibited high adsorption capacities (794.72 mg/g for MG and 129 mg/g for Pb²⁺). Crucially, in a binary system with 500 mg/L MG, it maintained high removal efficiencies (98.4% for MG and 93.8% for Pb²⁺), demonstrating exceptional anti-interference capability. Characterization revealed that site-specific adsorption mechanisms (π-π interactions for MG on the carbon matrix; complexation for Pb²⁺ on red mud components) led to minimal competition. Furthermore, MMBC-400 showed excellent regenerability, retaining over 85% removal after five cycles. This work presents a cost-effective and sustainable strategy for designing adsorbents for complex wastewater remediation.