Synthesis and Application for Pb2+ Removal of a Novel Magnetic Biochar Embedded with FexOy Nanoparticles

Biochar (BC) is a widely studied economic and environment-friendly material. However, its application is limited by its underdeveloped pore structure, small specific surface area, low degree of graphitization, and difficulty in being separated from liquids during the application process. Raw cotton contains almost 100% cellulose and has a high yield for preparing biochar. A novel type of magnetic biochar composite was prepared by the impregnation–calcination method using cotton and iron nitrate nonahydrate(Fe(NO3)3·9H2O). The material was characterized using scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, thermogravimetric analysis (TG), and specific surface area testing (BET). The results show that FexOy nanoparticles with a uniform morphology and an average particle size of less than 20 nm are embedded in the composite; the saturation magnetization strength of the composite material reaches 21.6 emu/g; and compared to the original biochar, the composite material has a larger specific surface area (326 m2/g). As an adsorbent, the composite material has a fast removal rate for Pb2+ of 95% in 50 min. The Langmuir model calculation results show that the maximum adsorption capacity of the composite for Pb2+ is 252.7 mg/g. FexOy-BC easily achieves solid–liquid separation and can be recycled for Pb2+ wastewater treatment through adsorption–desorption–regeneration.