Assessment of copper ferrite doped montmorillonite for efficient dye removal with insights into operational...

Copper ferrite (CuFe₂O₄) nanoparticles were successfully loaded onto montmorillonite (MMT) to develop a highly active adsorptive material (MMT@CuFe₂O₄) capable of removing acid red 18 (AR18) and methylene blue (MB) dyes. Textural, crystalline, and morphological properties were examined by XRD, SEM, FTIR, and BET analyses. A substantial rise in surface area from 12.55 to 43.55 m²/g and an increase in total pore volume from 0.0622 to 0.1295 cm³/g in MMT@CuFe₂O₄ relative to MMT demonstrates the successful introduction of mesoporous structures. Adsorption data revealed that the maximum removal efficiencies of MB and AR18 were 74.23% and 88.96%, respectively, under the same conditions of time (180 min) and temperature (35 °C). The adsorption equilibrium was best described by the Langmuir model, with maximum adsorption capacities (q_max) of 17.89 mg/g for MB and 16.26 mg/g for AR18, and high correlation coefficients (R² = 0.991 and 0.924). Kinetic data fitted the pseudo-second order model (R² > 0.97), indicating chemisorption as the dominant process, while the Elovich and intra-particle diffusion models further supported multilayer adsorption and intra-pore diffusion. The thermodynamic study demonstrated that adsorption proceeded spontaneously, as shown by the negative ΔG° values (- 3.29 to - 6.75 kJ/mol for MB and - 1.27 to - 9.01 kJ/mol for AR18), and was endothermic, with respective ΔH° values of 21.37 and 54.18 kJ/mol. Among the regeneration systems tested, electro-Fenton exhibited the highest recovery efficiency (75.63% for MB and 82.36% for AR18), whereas thermal regeneration showed the lowest (34.63% and 50.36%, respectively), demonstrating the superior regeneration performance of the EF method and the potential reusability of MMT@CuFe₂O₄ in practical dye removal applications.