Chitosan microspheres modified with poly(ethylenimine) enhance the adsorption of methyl orange from aqueous solutions

Chitosan (CS) microspheres were prepared by emulsion crosslinking, and the surfaces of the spheres were modified with poly(ethylenimine) (PEI) for preparing efficient adsorbents. Consequently, a series of PEI‐modified CS (CS–PEI) microspheres with different ion exchange capacities (IECs) was prepared and used for the adsorption of methyl orange (MO). The adsorption performance of CS–PEI increased significantly with the increase of the sphere IECs, and the maximum adsorption capacity of 400.00 mg/g was achieved at 303 K with CS–PEI–1275, which had the highest IEC in the experiments. The adsorption process of MO well fitted the pseudo‐second‐order kinetic and Langmuir isotherm models, and the process was favorable at low temperature. Thermodynamic analyses showed that the adsorption of MO by CS–PEI was a spontaneous and exothermic reaction. Furthermore, CS–PEI exhibited good reusability within seven cycles of adsorption–desorption.