Efficient removal of Cr6+ by magnetically modified biochar from aqueous solution:Removal mechanism investigation

The magnetic biochar is prepared by one-pot method using waste wooden building formwork as feedstock in the existence of the FeCl₃ for Cr⁶⁺ removal form wastewater. Characterization analysis indicates that magnetic biochar exists Fe₃O₄ with specific surface area of the 333.89–496.35 m²/g, contributing to Cr⁶⁺ removal. Cr⁶⁺ removal process can be well analyzed by the Pseudo-second order and Hill models with adsorption capacity of 30.41 mg/g. The adsorption process analysis indicates that Cr⁶⁺ removal mechanism includes surface complexation, electrostatic attraction, reduction and pore filling. The influence of Fe²⁺ on Cr⁶⁺ removal is analyzed, indicating Fe²⁺ participation into Cr⁶⁺ removal by reduction. The magnetic biochar has excellent reusability after three cycles. The Cr⁶⁺ removal process is also investigated using column adsorption experiment, indicating that magnetic biochar has column adsorption amount of the 56.64 mg/g. The economic feasibility of the magnetic biochar is investigated and calculated with the production cost of $2.48/1kg. The waste wooden building formwork is converted into the efficient magnetic biochar for Cr⁶⁺ removal from wastewater.