Multiscale synergistic effect of Fe/Mn oxides and biochar on bifunctional adsorption of tetracycline and Cu2+ in water at a wide pH range

Heavy metal and antibiotic compound pollution poses a serious threat to ecosystems and human health. In this study, a bifunctional magnetic biochar (FMBC) was prepared by a synergistic iron and manganese bimetallic modification strategy using discarded mushroom rods as biomass precursors. The Fe/Mn co-doping not only synergistically optimized the multilevel pore structure of the biochar matrix, but also endowed the biochar with ferromagnetic properties, which facilitates the separation of the solid-liquid after adsorption. It was demonstrated that FMBC exhibited exceptional adsorption performance for both tetracycline (TC) and Cu 2+ in the pH range of 2 to 12. In the TC-Cu 2+ composite pollution system (40 mg·L −1 TC and 10 mg·L −1 Cu 2+ ), the adsorption amounts of TC and Cu 2+ by FMBC were 14.53 mg·g −1 and 4.97 mg·g −1 after 60 min, respectively. Density functional theory (DFT) calculations were used to analyze the molecular configurations and electrostatic potential (ESP) of TC under different pH conditions, as well as the adsorption energies and charge transfers of TC and Cu 2+ in different adsorption configurations on the BC and FMBC surfaces, respectively. Due to the ferromagnetic properties, the FMBC can realize efficient solid-liquid separation within 10 s under the applied magnetic field. The removal efficiencies of more than 93.38 % and 96.66 % for TC and Cu 2+ were still maintained after 5 cycles. This study provides a novel approach for treating complex environmental pollution systems.