In-situ one-pot synthesis, characterization of magnetic hydrochar and its application as Fenton-like catalyst for the degradation of methylene blue dye

The widespread use of dyes in various industries has led to alarming levels of water pollution, posing significant environmental and health risks. This study presents biochar being a carbon-rich source, produced from Acacia koa pod covers has been used as a sustainable source to prepare Ak/BC-Fe₃O₄ magnetic nanocomposite, subsequently employed for Fenton-like degradation of methylene blue (MB) dye. FESEM-EDS revealed that the synthesized nanocomposite has a morphology of spherical magnetic nanoparticles being embedded on the biochar base and EDS further confirmed the synthesis of magnetic biochar by detecting only C, O, and Fe. The nanocomposite is mesoporous with a pore volume of 0.03204 cm³/g and a surface area of 7.11 m²/g as shown by the BET results. XRD substantiated the presence of an amorphous structure of biochar and the presence of ultra-small crystallites of Fe₃O₄ nanoparticles. FTIR signified the presence of specific functional groups for Fe–O and biochar whereas, XPS showed the peaks at 712.39 and 725.78 eV indicated the coexistence of Fe²⁺ and Fe³⁺. The nanocomposite is superparamagnetic with a saturation magnetization of 8.64 emu/g having remarkable magnetic separation capacity. Fenton-like degradation of MB dye in the presence of H₂O₂ revealed a first-order reaction with removal efficiency ranging between 82 and 96% in 120 min with convenient recycling ability for 7 cycles. Hence, this study underscores the outstanding characteristics and MB degradation efficiency of Ak/BC–Fe₃O₄, emphasizing its synthesis from sustainable plant biomass as a promising solution to address water pollution challenges associated with dye contamination.