Characterization and adsorption performance of magnetite nanoparticles-impregnated bentonite for methylene blue removal

Abstract

This study investigates the synthesis, characterization, and application of bentonite modified magnetite nanoparticles (MNPs-B) for methylene blue (MB) adsorption. Comprehensive characterization techniques, including X-ray fluorescence (XRF), X-ray diffraction (XRD), Fourier Transform Infrared (FT-IR), Transmission Electron Microscopy (TEM) and Scanning Electron Microscopy (SEM), confirmed the successful incorporation of magnetite into bentonite, with an eightfold increase in Fe₂O₃ content and a transition from a hexagonal to a cubic crystalline phase. Adsorption experiments demonstrated optimal MB removal efficiency at a dosage of 0.5 g/L, pH 8, an initial MB concentration of 50 mg/L, a temperature of 65°C, and a contact time of 90 minutes, achieving over 90% removal. The adsorption behavior followed the Langmuir isotherm model, suggesting monolayer adsorption, while kinetic studies aligned with the Pseudo-second-order model, indicating a chemisorptive process. Thermodynamic analysis revealed an exothermic and spontaneous adsorption mechanism. MNPs-B outperformed natural bentonite due to its larger surface area and enhanced adsorption capacity, although recyclability tests highlighted a slight decline in efficiency after repeated cycles. MNPs-B demonstrates enhanced adsorption performance for methylene blue, with potential applications in environmental remediation and magnetic separation processes. Future work should focus on improving regeneration techniques and scaling the process for industrial applications.