The sorbed mechanisms of engineering magnetic biochar composites on arsenic in aqueous solution

The aim of this study was to produce magnetic biochar for the removal of As (III) from the aquatic environment. Magnetic biochar (MBC) was prepared from corn straw‑derived biochar. Pristine biochar (BC) was impregnated with iron oxide and relative analyses were performed on the adsorption capacity of BC's and MBC's. After impregnation, the specific surface area of MBC800-0.6₃₀₀ increased from 79.66 to 309.7 m² g^-1 and superparamagnetic magnetization was about 9.75 emu g^-1 contributed by the contained Fe₃O₄. Results of MBC800-0.6₃₀₀ showed maximum adsorption capacity (Q_max) 22.94 mg g^-1 for As (III) based on Langmuir model which is 5.71 times higher than the adsorption capacity of BC800 (4.02 mg g^-1). The adsorption of As (III) increased significantly due to the successful loading of iron oxide and the increased oxygen functional groups that were confirmed by XPS and FTIR results. The removal of As (III) followed Langmuir isotherm model and pseudo-second-order (R² ≥ 0.99), indicated that the adsorption rate was monolayer and depended on the chemical adsorption process, respectively. Consequently, the simple preparation procedure and high adsorption performance suggest that MBC800-0.6₃₀₀ could be used as an environment-friendly and extremely effective adsorbent for As (III) removal from aqueous environment.