Biomass-Derived Magnetic Fe3O4/Biochar Nanoparticles from Baobab Seeds for Sustainable Wastewater Dye Remediation

Abstract

This work presents the synthesis and application of magnetic Fe3O4 nanoparticles supported on baobab seed-derived biochar (Fe3O4/BSB) for removing Congo red (CR) dye from aqueous solutions through an oxidative process. The biochar support offered a porous structure with a surface area of 85.6 m2/g, facilitating uniform dispersion of Fe3O4 nanoparticles and efficient oxidative activity. Fourier-transform infrared (FT–IR) spectroscopy analysis confirmed surface fictionalization after Fe3O4 incorporation, while scanning electron microscopy (SEM) images revealed a rough, porous morphology with well-dispersed nanoparticles. Thermogravimetric analysis (TGA) demonstrated enhanced thermal stability, with Fe3O4/BSB retaining ~40% of its mass at 600 °C compared to ~15–20% for raw baobab seeds. Batch experiments indicated that operational factors such as pH, nanoparticles dosage, and initial dye concentration significantly affected removal efficiency. Optimal CR removal (94.2%) was achieved at pH 4, attributed to stronger electrostatic interactions, whereas efficiency declined from 94.1% to 82.8% as the initial dye concentration increased from 10 to 80 mg/L. Kinetic studies showed that the pseudo-second-order model accurately described the oxidative degradation process. Reusability tests confirmed good stability, with removal efficiency decreasing only from 92.6% to 80.7% after four consecutive cycles. Overall, Fe3O4/BSB proves to be a thermally stable, magnetically recoverable, and sustainable catalyst system for treating dye-contaminated wastewater.