Effects and mechanisms of Fe/N co-doped magnetic biochar for efficient removal of single and multiple dye

The development of efficient, recyclable, and environmentally friendly biomass adsorbents is essential for mitigating resource waste and environmental pollution. In this study, iron and nitrogen co-doped biochar (2FN2ZC700) was synthesized using peanut shells as the raw material and ZnCl2 as a pore-forming agent through a one-step carbonization process. The structural properties of 2FN-2ZC700, along with its adsorption performance, synergistic effects, and adsorption mechanisms for the removal of methyl orange (MO), methylene blue (MB), and rhodamine B (RhB) dyes, were systematically investigated. The results demonstrate that 2FN-2ZC700 features a high specific surface area, a mesoporous structure, and abundant oxygen-containing functional groups, which collectively enhance its dye adsorption capacity. In multi-dye adsorption experiments, 2FN-2ZC700 showed a strong affinity for MO, achieving nearly 100 % removal, followed by MB and RhB. In the multi-dye system, MO exhibited preferential adsorption on 2FN-2ZC700, acting as a bridge that facilitated the adsorption of MB and RhB, particularly RhB, through electrostatic attraction and it-it interactions. In a ternary dye system, with each dye at an initial concentration of 100 mg/L, the bridging effect of MO increased the degradation rate and adsorption capacity of RhB by 19.46 % and 43.87 mg & sdot;g-1, respectively. Analyses of 2FN-2ZC700