Removal of cationic dyes from aqueous solutions using N-benzyl-O-carboxymethylchitosan magnetic nanoparticles

Magnetic nanoparticles prepared with iron oxides and N-benzyl-O-carboxymethylchitosan, an amphiphilic chitosan derivative, were prepared through the incorporation method and characterized by Fourier infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA), transmission electron microscopy (TEM), Mössbauer spectroscopy, and magnetization measurements. The γ-Fe2O3 nanoparticles proved to be spherical and well crystallized, and some aggregation behavior was observed. The particles containing the polymer presented saturation magnetization of 18.4 emu g−1 and roughly superparamagnetic behavior. The material was used to adsorb three cationic dyes from aqueous solution (methylene blue, crystal violet, and malachite green). The adsorption process preferably followed the Langmuir–Freundlich isotherm and pseudo-second-order kinetic model. The removal of the dyes was optimized using a 32 factorial design, and the initial dye concentration proved to be more influential in dye adsorption than the temperature of the system.

► The incorporation method produced nanoparticles with superparamagnetic behavior.
► The hydrophobic aromatic ring enhanced the dye adsorption.
► In optimization process the dye concentration was the most important factor.