Green synthesis of a novel Mn–Zn ferrite/biochar composite from waste batteries and pine sawdust for Pb2+ removal

Magnetic ferrite/biochar composites are a kind of promising adsorbents due to their high adsorption efficiency and facile magnetic separation; however, their synthesis is associated with high cost and secondary environmental impacts. In this study, a novel Mn–Zn ferrite/biochar composite (MZF-BC) is synthesized via a green two-step biocheaching and hydrothermal method using waste batteries and pine sawdust. Characterization results indicate that the introduced Mn–Zn ferrite particles are successfully embedded and coated on biochar (BC), and synthesized MZF-BC50 with 50% BC content exhibits best performance with a specific surface area of 138.5 m2 g−1, the saturation magnetization of 27.5 emu g−1 and CEC value of 53.2 mmol 100 g−1. The maximum adsorption capacity of Pb2+ is 99.5 mg g−1 based on the Langmuir sorption isotherm study at 298 K, and pseudo-second-order model accurately describes the adsorption process. Regeneration test suggests that MZF-BC50 can be efficiently reused for 6 cycles. In addition, it exhibits a good selective Pb2+ and Cd2+ removal performance in lead-acid battery wastewater. The results illustrate that this newly developed material has low cost and rapid remediation of Pb2+ as good application potential. [Display omitted] •Mn–Zn ferrite/biochar composite is synthetized by using a green two-step method.•MZF-BC50 with 50% biochar content exhibits best performance.•The maximum adsorption capacity of MZF-BC50 for Pb2+ is 99.5 mg g−1.•MZF-BC50 has a good selective Pb2+ removal performance in lead-acid battery wastewater.