Efficient removal of diclofenac sodium from water by chitosan/microcrystalline cellulose@polyethyleneimine hydrogel beads: Adsorption performance and mechanism study

Abstract

In this study, chitosan (CS) was combined with microcrystalline cellulose (MCC) to fabricate composite hydrogel beads. These beads were further modified through blending and grafting with polyethyleneimine (PEI) to develop chitosan/microcrystalline cellulose@polyethyleneimine (CS/MCC@PEI) composite gel spheres for the efficient adsorption of diclofenac sodium (DS) from aqueous solutions. The adsorbent was characterized using scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), and thermogravimetric analysis (TGA). The CS/MCC@PEI composite exhibited a spherical morphology with a porous structure, abundant surface functional groups, and a high adsorption capacity of 274.84 mg/g for DS. Kinetic studies revealed that the adsorption process followed the pseudo-second-order model, dominated by physical adsorption, with both surface and internal diffusion influencing the adsorption rate. The Freundlich isotherm model best described the adsorption behavior, indicating multilayer adsorption on heterogeneous surfaces. Environmental adaptability tests demonstrated minimal interference from co-existing anions and humic acid, while regeneration experiments confirmed excellent reusability (>77 % removal after five cycles). The adsorption mechanism involved electrostatic interactions and hydrogen bonding between the hydroxyl/amino groups of the composite and DS. These findings highlight the potential of CS/MCC@PEI as a cost-effective and sustainable adsorbent for DS removal from water.