Facile one-pot hydrothermal synthesis of cubic spinel-type manganese ferrite/biochar composites for environmental remediation of heavy metals from aqueous solutions

This study reports the facile synthesis of cubic spinel-type manganese ferrite (MnFe2O4)/biochar (MF/BC) composites via a one-pot hydrothermal technique. Multiple characterizations demonstrated that the MnFe2O4 spinel nanoparticles were successfully grown on the biochar, which provides magnetic separability with superparamagnetic behavior and effective adsorption performance for heavy metals (Pb(II), Cu(II), and Cd(II)). The adsorption kinetics and isotherms can be well described with a pseudo-second-order and Sips isotherm models, respectively. Comparative adsorption in multi-heavy metal systems (binary and ternary) indicated that the adsorption affinity of MF/BC composites toward heavy metals followed the sequence of Pb(II) > Cu(II) > Cd(II), which followed the order of their covalent indexes. Thermodynamic analysis revealed that the adsorption process was endothermic and primarily governed by physisorption. This study provides a feasible and simple approach for the preparation of high-performance materials for the remediation of heavy metal-contaminated wastewater in a cost-effective manner.