Enhanced Adsorptive Removal of Methylene Blue Using Kaolinite–MnFe₂O₄ Nanocomposites: Synthesis, Characterization, and Adsorption Mechanisms
J. Environ. Nanotechnol., Volume 15, No 1 (March 2026) pp. 405-417
Abstract
Kaolinite (K)-based matrices modified with manganese ferrite nanoparticles (MnFe₂O₄) were synthesized via a microwave-assisted route and evaluated as magnetically recoverable adsorbents for methylene blue (MB) removal from aqueous solutions. Structural, morphological, and compositional characteristics were investigated using X-ray diffraction (XRD), X-ray fluorescence (XRF), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and Brunauer–Emmett–Teller (BET) surface area analysis. XRD confirmed the presence of inverse spinel MnFe₂O₄, while XRF revealed a significant increase in iron oxide content, indicating successful incorporation of manganese ferrite into the kaolinite matrix. FTIR and SEM analyses supported surface modification through changes in functional groups and morphology. Batch adsorption studies demonstrated that MB removal efficiency was influenced by solution pH, adsorbent dosage, initial dye concentration, contact time, and temperature. Optimal adsorption performance was achieved at pH 5, an initial MB concentration of 40 mg/L, and an adsorbent dosage of 0.6 g/L, attaining approximately 91% removal efficiency. Adsorption equilibrium was best described by the Langmuir isotherm, indicating monolayer adsorption on a homogeneous surface. Kinetic data followed the pseudo-second-order model, suggesting that the adsorption rate was governed by surface interaction mechanisms rather than diffusion control. Thermodynamic analysis revealed that the adsorption process was spontaneous and weakly exothermic, with enhanced adsorption at elevated temperatures attributed to improved mass transfer rather than thermodynamic favorability. The MnFe₂O₄-modified kaolinite exhibited superior adsorption capacity and magnetic separability compared with natural kaolinite, along with good regeneration performance over multiple cycles. These findings demonstrate that MnFe₂O₄-embedded kaolinite matrices are promising, low-cost, and reusable adsorbents for dye-contaminated wastewater treatment.
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