Functionalized biochar-supported magnetic MnFe 2 O 4 nanocomposite for the removal of Pb( ii ) and Cd( ii )

In this study, a novel magnetic biochar-MnFe 2 O 4 nanocomposite (BC/FM) was prepared using low-cost corn straw and MnFe 2 O 4 by sol–gel/pyrolyzing route using egg white, which has abundant functional groups (–NH 2 and –COOH). Following that, its composition, morphology and structure was characterized by various techniques including SEM-EDX, BET, XRD, and VSM. Batch experiment of the adsorption for Pb( ii ) and Cd( ii ) including influence of pH, kinetics, isotherm and thermodynamics was also studied. The results demonstrated that biochar could effectively support MnFe 2 O 4 , which displayed high dispersion on the surface of the biochar and possessed abundant functional groups and high surface area contributing to superior performance on Pb( ii ) and Cd( ii ) removal. Therein, MnFe 2 O 4 with high magnetism is convenient for separating the magnetic BC/FM from an aqueous medium. Adsorption experiment results indicate that Pb( ii ) and Cd( ii ) removal by BC/FM was closely related to pH with the best value of pH 5.0, and the process reached equilibrium in 2 h. The adsorption process is well-described by the pseudo-second-order kinetic model and Sips (Freundlich–Langmuir) model. Thermodynamic studies suggest that the adsorption process is spontaneous and exothermic. The maximum experimental adsorption capacity of BC/FM is 154.94 and 127.83 mg g −1 for Pb( ii ) and Cd( ii ), respectively, in single-solute system, which is higher than that of some of the other adsorbents of biochar or biochar-based composites. In bi-solute system, the preferential adsorption order of BC/FM for the two metals is Pb( ii ) prior to Cd( ii ). Finally, FTIR and XPS analysis verified that the main mechanism of Pb( ii ) and Cd( ii ) removal by BC/FM is by forming Pb/Cd–O or complexation of carboxyl and hydroxyl and ion exchange. Therefore, the prepared magnetic BC/FM composite, as an excellent adsorbent, exhibited potential applications for the removal of Pb( ii ) and Cd( ii ) from wastewater.