2.6. Dye Adsorption Experiment

The dye adsorption study of the CT-Fe₃O₄ and JC-Fe₃O₄ NPs was performed by taking a known concentration of methylene blue (MB) (200 mg/L) solution and a definite quantity of MNPs (50 mg) in a conical flask (at pH~7), shaken thoroughly for 120 min at room temperature. At an interval of 20 min, the optical density (OD) was checked for each solution at 660 nm for adsorption kinetic study. For another set of experiments, a series of different initial concentrations (200 mg/L–500 mg/L) of MB were shaken (at pH~7, room temperature) with MNPs (50 mg) for 120 min, and the optical density (OD) was checked for each solution for adsorption isotherm study. While collecting the samples, the nanoparticles were removed by application of an external magnetic field [41].

C_o = initial concentration of MB dye only, C_e = concentration of MNPs solution (MB dye + MNPs) at equilibrium.