The removal efficiencies of phenol, 2-chlorophenol (2-CPh), and 4-chlorophenol (4-CPh) from aqueous solution with magnetic chitosan nanoparticles were investigated in this work. Chitosan-coated magnetite nanoparticles were successfully synthesized, characterizated, and applied as an effective magnetic biosorbent for the removal of phenol, 2-CPh, and 4-CPh from aqueous solutions. The characterization of synthesized magnetic chitosan nanoparticles was performed by Fourier transform infrared spectroscopy, transmission electron microscopy, scanning electron microscopy, dynamic light scattering, vibrating sample magnetometry analyses, and thermogravimetric analysis. Adsorption characteristics of phenolic compounds from aqueous solution on to magnetic chitosan have been studied and results indicated that the adsorption capacities were affected by initial pH values, initial concentration of adsorbates, dosage of adsorbent, and contact time. The adsorption of adsorbates followed with the pseudo-second-order reaction and equilibrium experiments were well fitted with the Freundlich isotherm model. Furthermore, it was found that the magnetic biosorbent can be regenerated and reused for five repeated cycles for the removal of phenol, 2-CPh, and 4-CPh and avoided secondary pollution of biosorbent to water.

In this study, glutaraldehyde cross-linked magnetic chitosan nanoparticles (GMCNs) were prepared through cross-linking modification of magnetic chitosan nanoparticles using glutaraldehyde as a cross-linker that exhibited excellent Metanil Yellow (MY) adsorption performance. The characterization of the GMCNs was performed by Fourier transform infrared spectroscopy, transmission electronmicroscopy, scanning electron microscopy, dynamic light scattering, and vibrating sample magnetometry analyses. Adsorption characteristics of MY from aqueous solution onto GMCNs have been studied. During the studies, various essential factors influencing the adsorption, like adsorbate concentration, amount of adsorbent, pH of the solution, and contact time have been monitored. The equilibrium was achieved within 17 h at pH 4, and the adsorption data obeyed the Langmuir equation with a maximum adsorption capacity of 625 mg/g and a Langmuir adsorption equilibrium constant of 5.2 × 10⁻⁴ dm³/mg at 25°C. The adsorption kinetics of MY at different initial dye concentrations was evaluated by the first-order and second-order models. The kinetic studies of MY adsorption showed that the adsorption process followed a second-order kinetic model. Furthermore, the GMCNs can be regenerated and reused through dye desorption in alkaline solution at pH 10. Adsorption results for reusability were 100, 93, and 65%, respectively, for three repeats.