Synthesis of Magnetic Chitosan/Poly (vinyl alcohol) Fe3O4 Nanocomposite and Evaluation of Its Efficiency in Removing Malachite Green Dye from Aqueous Solutions: A Kinetic, Isotherm, and Thermodynamic Analysis Approach

Objective: To address health concerns posed by cationic dyes such as malachite green in industrial effluents, this study aimed to synthesize a novel magnetic chitosan/poly (vinyl alcohol) (Fe₃O₄@CS/PVA) nanocomposite via in-situ co-precipitation and evaluate its dye removal efficiency through kinetic, isotherm, and thermodynamic analyses.
Methods: The Fe₃O₄@CS/PVA nanocomposite was prepared by immobilizing Fe₃O₄ nanoparticles within a CS/PVA polymer matrix. Characterization was performed using FT-IR, XRD, FE-SEM/EDX, BET, TGA, and VSM. Batch adsorption experiments were conducted at varying pH (3–11), adsorbent dosage (0.2–2 g/L), contact time (5–240 min), initial dye concentration (10–100 mg/L), and temperature (25–45 °C). Equilibrium data were fitted to Langmuir, Freundlich, and Temkin isotherms. Kinetic data were analyzed using pseudo-first-order, pseudo-second-order, and intraparticle diffusion models. Thermodynamic parameters were calculated using the van't Hoff equation.
Results: Fe₃O₄ nanoparticles were uniformly dispersed within the polymer matrix, with crystallite sizes of 11–13 nm, surface area of 66.8 m²/g, and saturation magnetization of 47.6 emu/g. Under optimal conditions (pH=7, dosage=1 g/L, time=120 min), removal efficiency reached 97.7%. Adsorption followed the Langmuir isotherm (R²=0.995) with maximum capacity of 83 mg/g, and pseudo-second-order kinetics (R²=0.998). Thermodynamic analysis revealed spontaneous (ΔG° = –6.8 to –9.5 kJ/mol), endothermic (ΔH° = +33.5 kJ/mol), and entropy-driven (ΔS° = +135.1 J/mol·K) adsorption. After five cycles, the adsorbent retained 87% of its initial efficiency.
Conclusion: The Fe₃O₄@CS/PVA magnetic nanocomposite, with high adsorption capacity, rapid kinetics, excellent stability, and easy magnetic separation, is an efficient and cost-effective adsorbent for removing malachite green from aqueous solutions.