Fabrication of Polyethyleneimine-Functionalized Chitosan Composite Microspheres for Efficient Removal of Diclofenac Sodium from Water: Behavior and Mechanism Study

Ecotoxicity of diclofenac sodium (DS) even at low concentrations makes it urgent to remove DS from water. In this work, chitosan microspheres were prepared by one-step reversed-phase emulsion method, and then, polyethyleneimine (PEI) was successfully grafted to form CS/PEI composites. The CS/PEI was characterized by Fourier infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and X-ray photoelectron spectroscopy (XPS). Effects of different influencing factors like material composition, dosage, pH, co-existing anions, and humic acid were investigated, and adsorption behavior of CS/PEI was explored by model simulation analysis. Results showed that adsorption process fits well with pseudo-second-order kinetic model and Langmuir adsorption isotherm model, indicating homogeneous and monolayer adsorption nature, and maximum Langmuir adsorption capacity was 364.12 mg/g at pH 6. The reusability of CS/PEI was confirmed by cyclic adsorption-desorption experiments, and electrostatic attraction and hydrogen bonding were the main mechanism for DS uptake by CS/PEI. Therefore, CS/PEI microspheres can be regarded as an efficient and convenient adsorbent for DS removal from aqueous media.