Influence of Mg-doped Ni_0.33Zn_0.33Co_0.33Fe₂O₄ Nanoparticles on the Methylene Blue Adsorption Efficiency Under Various Operational Parameters

Dye disposal in water has caused a serious environmental threat. Thus, ongoing research is driving efforts to explore solutions for this contaminant removal. Accordingly, the adsorption efficiency of ferrite nanoparticles has shown promising results for dye pollutant removal. Hence, in this study, Zn_0.33Ni_0.33Co_0.33-xMg_xFe₂O₄ nanoparticles were synthesized by chemical co-precipitation technique and studied under various operational parameters for the removal of methylene blue dye. The structural characterization of nanoparticles, held by XRD, confirms the successful phase formation with a small percentage of the hematite phase (< 8%). Additionally, the crystallite size decreased from 13.72 to 10.05 nm with Mg²⁺ increase from 0.00 up to 0.20. Consequently, the morphological characterization confirms the dependence of Mg²⁺ doping on the reduction of agglomeration between particles. The optical characterization was investigated by photoluminescence spectroscopy, highlighting an essential trend with the variation of excitation wavelength and Mg doping dependence. As the Mg content increases from 0.00 to 0.20, the surface area increases from 43.82 to 60.19 m².g⁻¹ whereas the pore diameter decreases from 16.65 to 12.49 nm. Among the synthesized samples, Zn_0.33Ni_0.33Co_0.33Fe₂O₄ nanoparticles exhibited superior adsorption performance, achieving the highest adsorption capacity of 90.4 mg.g⁻¹. In addition, the removal efficiency of methylene blue reached 95.8% for the Mg0.00 sample and 78.9% for the Mg0.20 sample, after a contact time of 30 min at pH 11. As the initial methylene blue concentration increased from 5 to 100 mg.L⁻¹, the removal percentage in the presence of Mg0.00 decreased from 98.4 to 79.8%. The adsorption process followed second-order kinetics and was well-fitted with the Freundlich isotherm model.