Preparation and Characterization of Magnetic Biochar Nanocomposites via a Modified Solvothermal Method and Their Use as Efficient Heterogeneous Fenton-like Catalysts

In this study, magnetic biochar nanocomposites (FeC–S) were prepared by employing ethylene glycol as a liquefaction agent of corn stalks and solvent for the solvothermal synthesis approach. The effects of urea/Fe3+ molar ratio, final solvothermal temperature, and residence time on the properties of FeC–S were investigated. Magnetic biochar synthesized through pyrolysis and the chemical co-precipitation method (FeC–P) was employed for comparison. As revealed by Fourier transform infrared spectroscopy, X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy/energy-dispersive X-ray spectrometry, vibrating sample magnetometer analysis, and Fenton-like oxidation of sulfamethoxazole, the impregnated iron in FeC–S presented as Fe3O4 nanoparticles with an average grain size of 8.9 nm, which makes the material magnetically separable. The FeC–S exhibited a higher Fenton-like catalytic activity than FeC–P, due to the highly dispersed and smaller crystalline size of loaded Fe3O4 particles, as well as the higher amount of oxygen-containing functional groups. The stability test showed that FeC–S can be easily recycled for five subsequent runs without significant activity loss.